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Evaluating the Performance of Corridors with Roundabouts (2014)

Chapter: Appendix A. Corridor Comparison Document

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Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-1 APPENDIX A. CORRIDOR COMPARISON DOCUMENT The Corridor Comparison Document (CCD) provides an overall framework for users to compare alternative corridor configurations and to objectively inform project decisions based on the unique context of each project. The CCD provides a broad approach for helping to inform corridor solution concept evaluations; it presents a framework that could adapt to the range of potential catalysts that might be the impetus for a particular project. There is a wide range of project catalysts, and projects may have a combination of contributing factors. Each project requires a unique range of considerations to evaluate potential solutions. Performance measures vary depending upon the project needs and context. Not all projects will have the same performance measures, nor will the full range need to be applied to each and every project. However, there are some performance measures that will generally apply to most projects. In some cases, a project may require special considerations to augment primary considerations. In such cases, the primary considerations alone may not be sufficient to differentiate the corridor solution needs. In those instances, adding additional considerations in a tiered approach could help introduce considerations that more clearly differentiate the project solution needs. CHAPTER 1: INTRODUCTION 1.1. PURPOSE OF DOCUMENT The CCD provides a sequence of potential criteria to be used when considering intersection control options on an arterial street with three or more major intersections that could potentially be controlled by a roundabout or traffic signal. This CCD is intended to help agencies choose between roundabouts and traffic signals on new or reconstructed arterials. 1.2. INTENDED USERS This document is crafted for the following types of users: Traffic engineers Transportation planners Roadway designers Preparers of environmental documents 1.3. SCOPE OF GUIDE This document guides users through the arterial corridor planning process, including project initiation, concept development, and alternatives analysis. A focus of this document is a sequential framework for selecting roundabouts or a traditional form and control (traffic signals or stop signs) for the intersection. For the purposes of this document, a corridor is considered to be an arterial street

Evaluating the Performance of Corridors with Roundabouts Page A-2 with three or more “major” intersections that could potentially be controlled with a roundabout or a traffic signal. Throughout the document, “major” intersections are defined as intersections needing roundabout, traffic signal, or stop control. “Minor” intersections are defined as intersections or driveways at which the side street is stop controlled (with major street uncontrolled) regardless of control at the major intersections. The principles in this document could also be adapted to shorter corridors or grid networks, but these applications are not explicitly addressed. The document provides guidance on evaluating alternatives and considering tradeoffs to make an informed intersection control decision. The document does not present standards or warrants for the use of a control device, as the choice is ultimately left to the user. Finally, the document focuses on corridor analysis, and does not explicitly address isolated intersections. 1.4. RELATIONSHIP TO OTHER RESOURCE DOCUMENTS The document acknowledges established resource documents that could also be used when assessing roundabout and signalized alternatives for a corridor. These documents include: Highway Capacity Manual (2010) Roundabouts: An Informational Guide, 2nd Edition (NCHRP Report 672, 2010) Highway Safety Manual, 1st Edition (2011) Manual of Uniform Traffic Control Devices (2009) A Policy on Geometric Design of Highways and Streets (Green Book) (2011) CHAPTER 2: USERS OF ARTERIALS This chapter provides information on the different users of arterials and how each user affects or is affected by traffic signals and roundabouts, particularly throughout a corridor. This chapter helps readers consider the various modal users, their unique needs, how they interact with one another, and how they are affected by or affect roadway design elements. Key modes and information on them (generally qualitative) are presented here. Identifying users and understanding their needs is a valuable exercise to establish key needs for a specific corridor. The function of a corridor and the modes it serves influence the project planning process (discussed in Chapter 3) and the selection and evaluation of performance measures (discussed in Chapter 4). Many performance measures are mode specific, and the relative weight and importance assigned to them when evaluating alternatives is, to some degree, a function of the volume and operating characteristics of a given mode. Addressing project catalysts and stakeholder priorities for a given corridor will influence selected performance measures and corridor evaluation needs. Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-3 2.1. PASSENGER CARS Passenger cars often dominate arterial streets, in terms of their percentage of the overall mode split. Historical planning and design of arterials has focused on serving the needs of passenger cars. Trends in design, such as “complete streets,” place greater emphasis on non automobile modes than historical approaches. Some arterial design choices and passenger car operating characteristics are noted here: Traditionally, most operational analyses of arterials have been auto based. In isolation, roundabouts generally have less vehicular delay than signalized intersections. However, roundabouts have geometric features that require all vehicles to slow (causing geometric delay), whereas traffic signals require non turning vehicles to slow or stop only during the red interval or when a queue is present (i.e., at the start of green). Traffic signals assign right of way and are usually timed to favor major street operations. This timing strategy increases minor street delay. On a corridor, traffic signals can be coordinated to some extent to reduce delay and the number of vehicle stops on the arterial. Factors such as high turning volumes and balanced directional flows limit the extent to which delay and the number of vehicle stops can be reduced. During low volumes and off peak periods, less delay generally occurs at roundabouts than at signalized intersections. Roundabouts generally have less severe vehicle crashes than signalized intersections. Single lane roundabouts generally have fewer crashes than signalized intersections. Signalized intersections sometimes require more turn or through lanes than roundabouts to serve queue storage needs. 2.2. BUSES Some corridors have scheduled service by public transit buses. Corridors may also serve a variety of other bus users such as school buses or charter buses. Some arterial design choices and bus operating characteristics are noted here: Public transit buses operating on a local route stop throughout a corridor to pick up and drop off passengers. Other modes, such as automobiles and bicycles, may not stop throughout a corridor unless directed to do so by a traffic control device. The diverse bus fleet has varying operational characteristics and design needs. The 2011 AASHTO Green Book has six types of bus design vehicles, including motor coaches, school buses, city buses, and articulated buses (5). At signalized intersections, bus only queue jump lanes are sometimes placed on the right side of the road to allow buses to bypass a queue of other vehicles at the start of the green phase. Similar bus bypass lanes

Evaluating the Performance of Corridors with Roundabouts Page A-4 are also used at roundabouts in some European countries and in at least one US location (Oregon). At signalized intersections, transit signal priority is sometimes used to extend green time to allow a bus to proceed through an intersection or start the green interval early to reduce the queue delay a bus experiences. 2.3. PEDESTRIANS Land use, proximity to walkable areas, and roadway design choices influence the volume of pedestrians on an arterial. An arterial without sidewalks or crosswalks may discourage pedestrian travel. For most users on most arterials, the arterial performance is primarily based on through movement operation. For pedestrians, the experience of crossing the corridor can influence their mode choice (i.e., whether or not to walk) and quality of experience. Except when crossing a street, pedestrians generally operate beyond the vehicle travel lanes of the roadway on sidewalks (if present), grass, or dirt. Some arterial design choices and pedestrian operating characteristics are noted here: Traffic signals can provide pedestrians with right of way at an intersection. All conflicting vehicle movements are stopped, although right turns on red and permissive left turns are sometimes allowed. Pedestrians must wait for the associated signal phase to receive this right of way. A four leg, single lane signalized or stop controlled intersection has 24 pedestrian vehicle conflict points, and a four leg, single lane roundabout has 8 pedestrian vehicle conflict points. The horizontal curvature of roundabouts slows vehicles. However, pedestrians must wait for a gap in the traffic stream before crossing. Pedestrian crossings at roundabouts may be signalized, although it is rare in the United States to date. Blind and visually impaired pedestrians face impediments to accessibility at roundabouts. Pedestrians must rely on gap and/or yield detection to identify when it is safe to cross. The HCM 2010 provides pedestrian level of service procedures for several types of roadways and intersections, including urban streets, signalized intersections, and stop controlled intersections (two way and all way). Pedestrian delay, signal timing, vehicle speed, and crosswalk length are some of the factors that influence pedestrian level of service. Vehicle speed, vehicle composition, buffers, and proximity to the traveled way influence the perceived quality of service for pedestrians as computed in the HCM 2010. Roundabout corridors may have lower segment speeds than arterial corridors depending on the intersection density. This is due to deflected vehicle paths and the resulting geometric delay at roundabouts. Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-5 2.4. BICYCLES Arterials have historically been designed without bicycle sensitive design elements, such as bicycle lanes or storm drains without openings parallel to the direction of travel. As a result, bicyclists experience a poor quality of service on many arterials. Bicycles are considered vehicles in most state uniform vehicle codes and, therefore, are required to follow the same traffic control as motorized vehicles, except where bicycle specific control is provided. Some arterial design choices and bicycle operating characteristics are noted here: At traffic signals, bicycles typically operate on the roadway (sometimes in a dedicated lane) and are typically controlled by vehicular signals. Sometimes bicycles operate on a multiuse path adjacent to the roadway. At roundabouts, bicycles may operate in the roadway with vehicles or, if available, they may use a multiuse path that is accessed via bicycle ramps on the entry and exit of the roundabout. When using a multiuse path, bicyclists cross any legs of the roundabout they encounter at pedestrian crosswalks. Along a road segment and away from intersections, bicyclists nearly always operate in the roadway. Riding on the sidewalk is prohibited in many jurisdictions in the United States, and multiuse paths are generally not common. If they prefer, bicyclists can dismount and walk through an intersection rather than riding through. The HCM 2010 provides bicycle level of service procedures for several types of roadways and intersections, including multilane highways, two lane highways, urban street segments, and signalized intersections. Shoulder width, pavement quality, vehicle volume, presence/absence of bicycle specific treatments, and the width of cross streets are some of the factors that influence bicycle level of service. 2.5. TRUCKS Trucks are present on nearly all arterial streets. Truck size and acceleration/deceleration performance influence the design requirements of many roadway elements—even if truck volume is low. As truck volumes increase, their effects on the corridor and other users become more pronounced. Some arterial design choices and truck operating characteristics are noted here: Arterial corridors are generally designed to accommodate trucks as large as a WB 62 or WB 67, and truck volumes can be significant. Some arterials are designed to accommodate trucks larger than a WB 62 or WB 67. Trucks generally travel slower than passenger cars and, due to their deceleration/acceleration characteristics, experience more delay when required to stop. Trucks require more physical space than a passenger car for turn lane storage and lane width to serve tracking, especially when multiple turn lanes are present.

Evaluating the Performance of Corridors with Roundabouts Page A-6 Trucks have greater air quality and noise quality impacts due to their size and weight. The speed of trucks, like other motorized vehicles, is limited by vehicle path radii at roundabouts. Oversize vehicles affect any intersection or corridor treatment. 2.6. EMERGENCY VEHICLES Arterials usually have few design elements specific to emergency vehicles. However, elements such as paved shoulders can be beneficial to all motorized users, including emergency vehicles. Some arterial design choices and emergency vehicle operating characteristics are noted here: Corridors are used by police, fire, and ambulance vehicles. The frequency of this use is driven, in part, by the proximity of emergency services (fire stations, police stations, etc.) to the corridor. Some jurisdictions use emergency vehicle preemption at traffic signals. This technology uses some means to detect emergency vehicles as they approach the intersection, typically to initiate a sequence of signal phases to favor the approach on which an emergency vehicle is located. Roundabouts have no emergency vehicle preemption options without using traffic signals. Roundabouts do not assign priority to vehicle movements like traffic signals do. Traffic signals require electricity, while roundabouts do not (aside from illumination). Roundabouts are less affected by natural disasters than traffic signals, and an increased number of emergency vehicles may be traveling following a natural disaster. Roundabouts generally have fewer injury crashes than signalized intersections, which may decrease the need for travel by emergency responders. Some corridors feature specific treatments for accommodating emergency vehicles, such as mountable median openings. 2.7. USER SUMMARY The user characteristics noted in this chapter are some of the many that may be relevant and appropriate to consider for a given arterial. In the early stages of the project planning process, practitioners should make every effort to determine the types of users anticipated on a corridor and their specific needs. Chapter 3 explains the project planning process in greater detail. Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-7 CHAPTER 3: PROJECT-PLANNING PROCESS This chapter is primarily wrien from the perspective of practitioners evaluating alternatives for reconstructing an existing corridor or constructing a new roadway where the alignment has already been determined. In other words, the process presented in this chapter is focused on intersection control and cross section decisions, not roadway alignment decisions. Exhibit 3 1 illustrates elements of a typical project planning and development process. Community stakeholders are generally involved throughout this project planning process. The heart of any project planning process is developing and analyzing alternatives. When following activities in the project initiation state, concepts can be developed and evaluated considering the identified needs of a specific corridor. This document aims to assist users with selecting and applying performance measures. Comparing roundabout and signal corridors can be challenging, as operational performance measures for roundabout corridors are less established than signal corridors. Performance measures are discussed in Chapter 4. Exhibit 3 1 depicts three primary activity stages: Project Initiation, Concept Development, and Alternatives Evaluation. The choice between any feasible alternatives—including roundabout and traffic signal alternatives—is generally not made until the planning process is nearly at an end. This allows for all categories of performance measures (traffic operations, safety, environmental, cost, community values, and others) to be applied to all feasible alternatives before any are accepted or rejected. Often, a preferred alternative will not have the highest rating for every performance measure or even group of performance measures. Therefore, this document emphasizes the need to evaluate multiple alternatives before selecting a preferred alternative.

Evaluating the Performance of Corridors with Roundabouts Page A-8 3.1. PROJECT INITIATION 3.1.1. Understanding of Context Arterial streets can serve a wide variety of functions, users, and volumes. For example, some arterial streets serve large volumes of through vehicles, while others provide access to intensely developed land. An urban arterial may feature on street parking, one way travel, and bicycle lanes. A rural arterial may have one travel lane in each direction, with a posted speed of 55 miles per hour or more, and pass through primarily undeveloped land. When undertaking a planning effort for a new or improved corridor, a practitioner must first understand the context of the roadway. Where Exhibit 3-1: Corridor Planning Process Project Initiation Concept Development Alternatives Analysis Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-9 is it located? Who will it serve? What will be the purpose of users’ trips on the roadway? What type of roadway and place are stakeholders looking to create? Exploring these questions and others at the earliest stages of the project initiation process helps provide an understanding of the project’s context. This context will be a guiding principle throughout the corridor planning process. Identifying goals and objectives, developing alternatives, selecting performance measures, and evaluating and selecting alternatives should be based upon a project’s unique contextual environment. Developing alternatives that match a roadway’s context presents users with a self describing roadway. For example, using curb and guer on an urban arterial in a residential area reinforces an urban context, whereas an open section could suggest a higher speed environment to drivers. 3.1.2. Identify Project Goals and Objectives & Project Users Project goals and objectives will vary according to the context of a project and specific community needs. Therefore, performance measures will also vary depending upon the project needs and context. Not all projects will have the same criteria, nor will the full range of possible criteria need to be applied to each and every project. Projects typically begin by identifying an existing or future need in the transportation system. Project needs may arise from a variety of catalysts. Each catalyst will influence the project goals and selection of performance measures. During these first steps in the planning process, specific solutions considered might include roundabout or signalized concepts. Project context and the unique needs of each corridor often require more than an early project visioning effort. Project goals and objectives are typically referred to during subsequent stages of the planning process to evaluate whether the alternatives effectively meet the project needs. At the most fundamental level, project catalysts could include the following general categories, with most projects potentially including various elements of other categories: A new greenfield corridor; An existing signalized corridor being evaluated because of capacity or safety performance; An existing roundabout corridor; A corridor with a specific access management focus; A corridor that is explicitly focused on multimodal considerations; A corridor project driven by community enhancement objectives, speed management needs, or economic development or growth opportunities; or, A hybrid corridor containing roundabouts, traffic signals, and stop controlled intersections. As discussed in Chapter 2, arterials serve a wide variety of users. The degree to which these users are present can vary greatly among arterials. Likewise, the

Evaluating the Performance of Corridors with Roundabouts Page A-10 needs, goals, and objectives in some corridors may predominantly relate to deficiencies for one or several user groups, but not all. Therefore, during this stage of the planning process, planners and engineers should consider the needs of the community and begin to identify relevant performance measures for the corridor—including those that will vary with roundabouts and traffic signals—to help assess the performance of each control device. 3.1.3. Select and Prioritize Performance Measures Corresponding to the wide variety of contexts in which arterials exist, there is a wide variety of performance measures available for analyzing arterial concepts. The choice between traffic signals and roundabouts for intersection control is one of many decisions faced by those planning a corridor. Practitioners must choose which performance measures are of importance to a given project, and which are not. Stakeholder input and budget constraints often influence this choice. Performance measures should be chosen in the early stages of the project planning process, when a practitioner has gained an understanding of a project’s context, but has yet to begin developing alternatives. In this document, performance measures are grouped into six categories: Quality of service measures. Examples include delay and travel time for all modes. Safety measures. Examples include the predicted number of fatal/injury crashes or expected relative difference in crash frequency. Environmental measures. Examples include effects on public facilities, impacts to wetlands, and fuel consumption. Cost measures. Examples include economic benefits associated with a project, the capital cost of a project, and the economic cost of crashes. Community values. Examples include livability, place making, and community acceptance. Other measures. Examples include policy choices such as “roundabouts first,” tort and other legal issues, access management, economic development, speed management, and community acceptance. While many performance measures are generally worthy of consideration, ranking is necessary to guide the comparison process. This document advocates a tiered approach to ranking project considerations. Certain tiers have broader application to all arterials, and others have lesser applicability or may apply primarily to certain contexts. In some cases, adding elements from subsequent tiers may help differentiate concepts. For example, if two corridors exhibit relatively little difference using the initial tier considerations, subsequent tier considerations could provide differentiating performance evaluation results to inform project decision making. A possible classification is as follows: Tier I – critical considerations for most corridors (e.g., delay, safety, travel time, constructability). Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-11 Tier II – items that apply to many locations (e.g., access management, pedestrian accessibility). Tier III – issues that may impact a smaller subset of corridors (e.g., effects on specific adjacent land uses such as schools or hospitals, familiarity of corridor drivers with certain control devices). Exhibit 3 2 presents a number of performance measures that may be relevant when evaluating concepts for an arterial corridor. Additional information on these specific performance measures and their application is provided in the next chapter of this document.

Evaluating the Performance of Corridors with Roundabouts Page A-12 Exhibit 3-2: Performance Measures Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-13 Conceptually, the performance measures can be separated into two broad categories: quantitative and qualitative. Quantitative performance measures include delay, predicted crash frequency, and construction cost. These measures are evaluated with models, data, and computations. Qualitative performance measures include auto impacts to pedestrians and bicyclists, livability, and land use considerations. Both categories of performance measures may be used when evaluating corridor concepts. All projects are unique, and key performance measures will differ from project to project. For each project, relevant performance measures should be selected based on the project initiation activities outlined in Exhibit 3 1. In many cases, it is helpful to prioritize these measures into two or three tiers. Performance measures that are most valued by the community and relevant to the goals and objectives of the project would be placed into Tier I. The process of selecting and tiering performance measures is demonstrated in the example applications at the end of this appendix. 3.2. CONCEPT DEVELOPMENT 3.2.1. Develop Alternatives and Conduct Preliminary Analysis Developing alternatives and conducting preliminary operations and safety analyses is the heart of the project planning process. For an arterial project in which roundabouts and traffic signals are being considered, there may be more than two alternatives, as there are many design elements beyond intersection control to consider. For example, a corridor could have a two way left turn lane (TWLTL) or a raised median, and it could have sidewalks immediately adjacent to the curb or sidewalks offset from the curb by several feet. To isolate the comparison of these midblock elements from the comparison of intersection control, it may be helpful to develop alternatives in pairs; for example: Alternative 1 o Alternative 1A: Arterial with four travel lanes, TWLTL, and signalized intersections. o Alternative 1B: Arterial with four travel lanes, TWLTL, and roundabouts. Alternative 2 o Alternative 2A: Arterial with four travel lanes, raised median, and signalized intersections. o Alternative 2B: Arterial with four travel lanes, raised median, and roundabouts. Using paired alternatives allows for comparing roundabouts, signals, and stop control when all other roadway elements are the same. Conversely, it allows for Project Initiation Concept Development Alternatives Analysis

Evaluating the Performance of Corridors with Roundabouts Page A-14 a comparison of alternatives with different midblock elements (such as a TWLTL versus a median) when intersection control is the same. Developing alternatives should be an iterative process. A preliminary traffic assessment of an alternative may reveal it is infeasible or may dictate changes in the number of lanes or other major design elements. Some alternatives, while found to be infeasible, may have certain feasible and desirable features that can be incorporated into other alternatives. Examples of design elements of arterials that may differ between alternatives are listed below: Control at major intersections (traffic signal, roundabout, stop control, or uncontrolled) Median type Number of lanes Width of lanes Presence of sidewalks Presence of bike lanes Access/control at driveways and side streets Access management Roadway cross section Right of way Design speed Intersection spacing Presence of on street parking A number of planning level analysis tools are available to practitioners and are appropriate to apply at this stage of the project planning process. For example, critical movement analysis (CMA) is an analytical technique that estimates the volume to capacity ratio of an intersection using hourly traffic volumes, signal phasing, and lane configuration. CMA can be performed iteratively to assess the adequacy of different lane configurations. Section 7.4 of the 2004 FHWA publication Signalized Intersections: Informational Guide provides guidance on conducting CMA (4). For roundabouts, NCHRP Report 672: Roundabouts: An Informational Guide offers several planning level tools (2). Exhibit 3 12 of that document indicates ranges of AADT and left turn volume percentages at which single lane roundabouts or double lane roundabouts may operate acceptably. Exhibit 3 14 of NCHRP Report 672 provides similar guidance based upon hourly traffic volumes rather than AADT, and does so on an entry by entry basis rather than for the roundabout as a whole. Practitioners can use these tools and others to determine lane needs at the earliest stages of the project planning process without conducting a full operational analysis. Use of these tools is illustrated in the example applications in Chapter 5. Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-15 Sometimes, the number of through lanes on a corridor is pre determined. For example, an agency may have a programmed project that calls for a four lane roadway between two points. In this situation, planning level tools may be helpful to determine side street lane needs, but may have limited applicability to the major street lane needs. 3.2.2. Conceptual Layouts Once alternatives are developed and lane needs are known, practitioners can produce conceptual layouts. These layouts can gauge impacts on the built and natural environment, connections and interaction with other elements of the transportation system, and other elements. At this time, it may become clear some alternatives are infeasible and should be eliminated from consideration. Often this can be because an intersection capacity improvement is too impacting to the surrounding land uses or because the proposed arterial typical section is too impacting in total footprint. In another example, an arterial cross section that adds travel lanes at the expense of pedestrian and bicycle facilities (to avoid right of way acquisition) may prove to be infeasible if pedestrian and bicycle facilities are a project requirement. Production of conceptual layouts may identify opportunities to revise concept designs. Design impacts may require reassessment of traffic operations and lane needs. For example, traffic analysis may indicate double left turn lanes are required on both major street approaches to a signalized intersection, and a sketch may identify undesirable property impacts. Through iteration, an additional corridor concept with closer spacing of intersections, distribution of turning movements, and single left turn lanes could be developed. 3.3. ALTERNATIVES ANALYSIS 3.3.1. Apply Performance Measures Practitioners should apply selected performance measures to all alternatives developed during previous steps of the planning process. At least one performance measure from each of the six major groups listed in Exhibit 3 2 (traffic operations, safety, environment, cost, community values, and other) is likely to be relevant to a typical project. The tiering concept presented in Section 3.1.3 is helpful for assigning a relative importance to each performance measure. Chapter 4 presents several techniques to help practitioners compare alternatives. Example applications of the performance measures are presented in Chapter 5. 3.3.2. Identify Preferred Alternative This is the point within the planning process at which practitioners must select one of the alternatives based upon the previously conducted evaluation. This choice will determine intersection control (roundabouts, traffic signals, or something else) and other major elements of design. Project Initiation Concept Development Alternatives Analysis

Evaluating the Performance of Corridors with Roundabouts Page A-16 3.3.3. Refine Preferred Alternative After selecting an alternative, increasingly detailed design activities will begin and culminate with a final design effort to produce construction documents. At each stage of project programming, environmental evaluations, preliminary engineering, and final design the preferred alternative is detailed sufficiently to address approval and documentation for each step leading to construction. During this refinement, there is lile opportunity to change from roundabout to signal control or vice versa. The choice of control device is made prior to this stage. CHAPTER 4: PERFORMANCE MEASURES This chapter presents information on the performance measures previously listed in Exhibit 3 2. The performance measures discussed in this chapter are grouped into six categories and represent many of the things commonly considered when evaluating corridor arterials. The performance measures presented here are not an all encompassing list. Some corridors will have unique contexts and needs, and considering relevant performance measures in addition to those presented here may be needed to adapt to unique project needs. The performance measures are user based (such as operations and safety) and non user based (such as environmental impacts and costs). For user based evaluations, this document will emphasize multimodal performance capturing the experience of various potential corridor users. 4.1. OPERATIONAL EVALUATION Operational evaluations usually consider peak and off peak times of the day and different analysis years, such as the opening year and the design year. Operational performance measures can be grouped into supply side measures and demand side/user experience measures. Supply side measures include capacity, corridor throughput, and volume to capacity ratio. These measures are not directly experienced by corridor users, but can impact user experience. Demand side measures, such as delay and travel time, are experienced by users each time they pass through a corridor. When possible, this document uses a multimodal approach to performance measures. Delay, for example, is experienced by drivers, pedestrians, bicyclists, and bus riders. This approach is consistent with the HCM 2010, which includes delay and level of service procedures for pedestrians and bicyclists in addition to autos. While not used for every evaluation, commonly used operational performance measures are listed in Exhibit 4 1, along with additional guidance and methods for assessing each performance measure. 4.1.1. Corridor Travel Time The HCM 2010 includes a travel time procedure for Urban Streets, defined as a street “with relatively high density of driveway access located in an urban area and with traffic signals or interrupting STOP or YIELD signs no further than 2 mi Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-17 apart” (1). Although theoretically applicable to any urban street, the procedure was developed using data from signalized corridors and does not have roundabout specific computational steps. The NCHRP project that produced this CCD also collected field data at roundabout corridors and developed a travel time procedure for them within the framework of the HCM 2010 Urban Streets procedure. Example Application #1 illustrates the use of the roundabout specific urban street travel time procedure developed as part of this project. Performance Measure Assessment Techniques and Notes Corridor Travel Time For the auto mode, practitioners can measure corridor travel time in the field, estimate it with the Urban Streets procedure of the HCM 2010 (Chapters 16 and 17), or estimate it with software. A common means of field measurement is the floating car technique, in which a test car is driven the length of the corridor and “floats” in the traffic stream by passing and being passed by the same number of vehicles. The Urban Streets procedure of the HCM computes the travel speed along a corridor; the length of the corridor can be divided by the travel speed to determine travel time. Finally, simulation models such as VISSIM or deterministic software packages such as SYNCHRO also provide estimates of corridor travel time. Once corridor travel time is known, it can be used to determine facility level of service for the auto mode. Practitioners can conduct travel-time studies of non-auto modes in a similar manner. An individual can travel the corridor on foot, by bike, or onboard a bus and measure the resulting travel time. The Urban Streets procedure of the HCM also computes travel speed for these non-auto modes, which can be converted to travel time. Many transit vehicles are now equipped with automatic vehicle location (AVL) technology, and data from this system can be analyzed to compute travel times. Finally, simulation models such as VISSIM can provide estimates of corridor travel time for non-auto modes. Field research conducted as part of this NCHRP project measured auto travel time on nine roundabout corridors and also estimated auto travel time on nine equivalent signalized corridors. These data are summarized in the main project report. Intersection Delay The HCM provides procedures for computing auto delay at signalized intersections, stop-controlled intersections, and roundabouts. The signalized intersection procedure also computes pedestrian and bicycle delay, and the two- way stop-control (TWSC) procedure also computes pedestrian delay. In addition to the HCM, practitioners commonly use deterministic software such as SYNCHRO, SIDRA, ARCADY, or RODEL to compute auto delay at intersections. Practitioners use simulation software such as SIMTRAFFIC and VISSIM as well, but to a lesser degree. These types of software also provide pedestrian, bicycle, and transit delay data to varying degrees. Operating Speeds and Speed Profiles Practitioners measure vehicle speeds at points along a corridor (spot-speeds) in the field with a radar or lidar gun, or within a simulation model. A series of spot- speeds collected along a corridor can be graphed to produce a speed profile; this allows a practitioner to understand how speeds vary along a corridor. A speed profile can also be generated by a GPS device that is onboard a vehicle while a travel-time run is performed. As part of this NCHRP project, field-measured speed profiles of nine roundabout corridors were constructed using GPS data. The data are summarized in the main project report. Exhibit 4-1: Operational Performance Measures

Evaluating the Performance of Corridors with Roundabouts Page A-18 Performance Measure Assessment Techniques and Notes Queues The HCM provides procedures for determining queue lengths at signalized, stop- controlled, and roundabout-controlled intersections. Practitioners may also use deterministic software such as SYNCHRO and SIDRA or simulation software such as SIMTRAFFIC and VISSIM to estimate queue lengths. Practitioners generally analyze 50th-percentile and 95th-percentile queues, as these represent average and reasonable worst-case values, respectively. When queues form at roundabouts, they are generally “rolling” queues in which vehicles in queue advance one car length at a time as vehicles at the head of the queue enter the roundabout. Intersection Capacity Intersection capacity is generally determined for the sake of computing a volume- to-capacity (v/c) ratio. The HCM provides procedures for determining the v/c ratio of signalized, stop-controlled, and roundabout-controlled intersections. Deterministic software such as SYNCHRO, SIDRA, ARCADY, and RODEL also provide v/c ratios. Arterial Capacity In most cases, the capacity of an arterial is determined by the capacity of intersections along it. Exceptions to this include rural arterials and access- controlled arterials, both of which exhibit uninterrupted flow conditions. Critical Headways for Permitted Movements Delay at and capacity of unsignalized intersections is determined in part by a driver’s acceptance or rejection of an available gap in the conflicting traffic stream. The average minimum gap a driver will accept is measured as the critical headway. Critical headway is usually determined by detailed reduction and analysis of video footage of an intersection. Auto Traffic Impacts on Pedestrians and Bicyclists When crossing a high auto-volume street, pedestrians and bicyclists will generally experience more delay compared to crossing a low auto-volume street. This is an example of a quantifiable impact that can be measured in the field or computed. Autos can also impact pedestrians and bicyclists in ways that are more challenging to measure and quantify. For example, bicyclists may have an improved experience on a roadway as shoulder width increases, vehicle speeds decrease, and the number of driveways decreases. The HCM 2010 provides pedestrian and bicycle level of service, which is based in part upon the comfort of these users as they travel along a roadway or through an intersection. Considering the context of a roadway and the degree of auto, pedestrian, and bicycle activity will help in selecting appropriate performance measures. Pedestrian and Bicycle Impacts on Auto Traffic Pedestrians and bicyclists can impact auto traffic operations on an arterial, especially as their volume increases. The intricacies of these interactions are often site-specific and not fully captured in operational models. Practitioners should perform field visits to qualitatively assess such issues. Bus Operations The Transit Capacity and Quality of Service Manual (TCQSM) provides a number of measures that gauge bus performance and rider experience on arterial roadways (6). Delay to Left-Turn Movements The same techniques used to assess intersection delay can be used to assess the delay for individual movements, including left turns. The manner in which a left turn is conducted at a roundabout is different than at a signalized intersection. Lane Utilization Traffic analysis procedures in HCM and software packages generally assume vehicles are equally or nearly equally distributed across multiple lanes serving the same movement. On an existing facility, this assumption can be verified in the field and analysis adjusted as necessary. Exhibit 4-1 Continued Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-19 Performance Measure Assessment Techniques and Notes Side-Street/ Driveway Traffic Performance at TWSC Intersections Side streets and driveways can experience several operational challenges. If the major-street volume is sufficiently high, side streets and driveways may experience failing levels of delay regardless of their traffic volume. This is especially true for the left-turn movement, which may be made directly from the side street or made with a right turn followed by a U-turn. The issue can be compounded if a queue from a signalized intersection or roundabout blocks the side street. The HCM, deterministic software, and simulation models all compute side-street delay. Simulation models allow assessment of indirect left-turn treatments. Pedestrians also face challenges at TWSC intersections because of the lack of a control device to regulate major-street traffic. The Urban Streets procedure of the HCM 2010 (Chapters 16 and 17) contains a “roadway crossing difficulty factor” that quantifies this difficulty factor. Side-Street Traffic Performance at Major (signal/ roundabout) Intersections The same techniques used to assess intersection delay can be used to assess the delay for individual approaches. Unlike roundabouts, traffic signals can be timed to favor certain movements, and the degree to which a movement is favored can be changed by time of day or in response to traffic demands. Number of Stops The number of times a user stops while traveling the length of a corridor is a performance measure that is similar to delay. However, if delay is equal, users may prefer fewer, longer stops versus more frequent, shorter stops. Practitioners can use field measurements or a simulation model to determine the number of stops. Additional Bicycle- and Pedestrian-Only Performance Measures Some land-use developments may require considering unique pedestrian and bicycle needs. For example, a school or sports complex may have especially high crossing needs. Emergency Vehicle–Only Performance Measures Understanding emergency response needs early in the project-initiation stage may influence project decisions. For example, if preemption is an absolute need, signals may be favored over roundabouts. Likewise, understanding emergency vehicle design could potentially influence roundabout geometric design elements such as mountable curbs, truck apron design, or entry and exit lane widths. Truck Performance Measures Some arterials serve land uses such as ports or industrial facilities that generate a high percentage of truck trips, and may have unique operating characteristics and design needs. 4.2. SAFETY EVALUATION The Highway Safety Manual (HSM) provides a quantitative way of assessing and comparing the safety performance of many types of roadways and intersections through the use of safety performance functions (SPFs) and crash modification factors (CMFs) (3). However, quantitative safety analysis is still a relatively new field and, in some situations, the use of surrogate safety measures is still appropriate. This is especially true for non auto modes, as there has been less quantitative safety research in this area. Exhibit 4 2 lists a sample of safety performance measures and provides guidance on their application. Exhibit 4-1 Continued

Evaluating the Performance of Corridors with Roundabouts Page A-20 Performance Measure Assessment Techniques and Notes Predicted Vehicle Crash Frequency Chapter 12 of the HSM contains SPFs for segments and intersections of urban and suburban arterials. In general, fewer crashes are expected at a single-lane roundabout than at a signalized intersection. Example Application 1 illustrates the application of SPFs. Changes in Vehicle Crash Frequency or Severity The HSM contains CMFs for changing intersection control. For example, converting a signalized intersection to a roundabout has a CMF of 0.52. This means that, at a given intersection, only 52% of the crashes that occurred with a signal are expected to occur once the signal is replaced by a roundabout. Converting a minor-road stop-control intersection to a roundabout has a CMF of 0.56. The HSM also contains CMFs for conversion of specific intersection types in specific environments (such as a rural, four-leg, TWSC intersection) to roundabouts. The CMFs mentioned above are for all settings, all types of crashes, and all severities. The HSM also provides more specific CMFs for certain settings (such as urban or suburban, one or two lanes), types of crashes, and severities of crashes. Example Application 1 illustrates the application of CMFs. Conflict Points Draw all vehicle paths at an intersection and count the number of locations where they cross. Bicycle and pedestrian paths could be added as well if assessing conflicts for these modes. In general, there are fewer conflict points at roundabouts than at signalized intersections. A four-leg single-lane roundabout has 8 vehicle/vehicle and vehicle/person conflict points, and a four-leg signalized or stop-controlled intersection with single-lane entries and exits has 32 vehicle/vehicle and 24 vehicle/person conflict points. Example Application 3 contains additional discussion of conflict points. Surrogate Measures Examples of surrogates: Presence of vehicles in the crosswalk when in use by a pedestrian, Speed differential between bicycles and autos, Number of close passes of bicyclists by autos, Vehicles parking in bicycle lanes, and Conflict points. Surrogates such as these can be measured in the field or estimated from preliminary plans. 4.3. ENVIRONMENTAL EVALUATION Environmental evaluations are broad and consider impacts to the natural and built environment due to the construction and operation of the corridor. If a roundabout corridor and a signal corridor are evaluated with the same general roadway alignment, certain environmental impacts may differ only negligibly from one alternative to the other. However, different intersection footprints or roadway cross sections could result in differing impacts, especially in sensitive areas. In general, roundabouts allow capacity to be added to the intersections with less impact to the roadway segments, compared to signalized corridor needs. Environmental evaluations of different alternatives are conducted through processes outlined in state and federal regulations and guidance documents. The National Environmental Policy Act (NEPA) guides federal and most state environmental regulations. Examples of state level regulations include the State Exhibit 4-2: Safety Performance Measures Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-21 Environmental Policy Act (SEPA) in many states or the California Environmental Quality Act (CEQA). Exhibit 4 3 lists a sample of environmental performance measures, many of which are a component of federal and state evaluations, and provides guidance on their application. Performance Measure Assessment Techniques and Notes Impacts to Sensitive Features Sensitive features include wetlands, historic properties, cultural features, habitat of protected species, public facilities such as parks and schools, historic main streets, and other various protected areas. The extents of these areas are generally identified by experts and then mapped. The location of these features is compared to the footprint of a proposed alternative to determine impacts. Impacts to Private Property (including access to it) The need to restrict access at certain points along a roadway is determined by agency guidelines and standards and engineering practices. Likely access restrictions can be determined at the conceptual planning stage using simple sketches or engineering drawings. Roundabout and signal corridors often apply different access-management strategies at intersections and midblock locations. This performance measure may often be a key part of environmental analysis of traffic signal and roundabout alternatives. Specific State and Local Environmental Performance Measures Jurisdictions may have additional performance measures used in their evaluation process. Emissions and Fuel Consumption Although not part of the NEPA process, software tools can be used to predict emissions and fuel consumption. Examples include traffic analysis software such as SIDRA and VISSIM and software specifically designed for emissions analysis such as the Environmental Protection Agency’s MOBILE. Noise Software models may be used to predict the noise level at a location of interest such as a house or school. The differences in speed and acceleration/deceleration between roundabout operation and signalized intersection operation may result in different levels of noise. Light Pollution Software models may be used to predict the light level at a location of interest such as a house or park. Lighting requirements for roundabouts and signalized intersections vary from jurisdiction to jurisdiction. Amount of Impervious Surface The amount of paved area is typically measured during the development of pavement and grading plans. Roundabouts may require more pavement area at the intersection compared to a traffic signal but less on the entries and exits. 4.4. COSTS Like environment evaluations, cost evaluations consider many different elements of a project. In addition to capital construction costs and various costs related to maintaining a facility, this category of performance measures also includes costs to users and the community. Exhibit 4 4 lists a sample of cost related performance measures and provides guidance on their application. Exhibit 4-3: Environmental Performance Measures

Evaluating the Performance of Corridors with Roundabouts Page A-22 Performance Measure Assessment Techniques and Notes Construction Costs Pre-construction Costs (such as design) Often this is estimated as a percentage of the construction cost. Right-of-Way Acquisition Cost This is the value of privately-owned land to be acquired for the project. Exhibits 3-17 and 3-18 of NCHRP Report 672 show the different right-of-way needs of typical signalized intersections and roundabouts. Capital Construction Cost During the evaluation of alternatives, develop cost estimates commensurable with the level of detail of the plans. Maintenance Costs Annual Maintenance Cost Elements of a roadway requiring maintenance include lighting, landscaping, grass shoulders or medians, pavement, signs, and traffic signal equipment. Electrical Consumption Cost Street lights and traffic signals require electricity. Future Expansion Cost Some roadways and intersections are designed to be expanded in the future, and the costs associated with this expansion can vary. User Costs and Benefits Lost or Gained Productivity The amount of time a person spends in congested conditions is a lost opportunity to do other, more productive things and practitioners can assign a monetary value to this time. The value of time for commercial drivers on the job is generally greater than the value of time for personal trips by non-commercial drivers. Cost of Injuries Due to Crashes A person injured in a crash is faced with medical bills, property damage, lost productive time, and pain and hardship. Chapter 7 of the HSM quantifies the costs associated with these elements. Fuel Consumption As discussed in Section 4.3 of the CCD, the amount of fuel consumed by all vehicles under different alternatives can be estimated. The average gasoline retail price then determines the associated cost of the fuel. Community Costs and Benefits Emissions and Air Quality Emissions from vehicles using a roadway and the resulting air quality have the potential to negatively impact communities adjacent to a roadway. Development and Impact of a Roadway on Businesses New or improved roadways may spur economic activity by creating access to undeveloped land or reducing the travel time existing in developed areas. Access and Mobility Roadways provide a mixture of access and mobility. An increase in one of these elements results in a decrease of the other. The degree to which each is provided should be based upon the needs of the surrounding community and the functional classification of the roadway. 4.5. COMMUNITY VALUES Transportation facilities exist to serve people and communities. Practitioners consider the desires of communities and stakeholders in the vicinity of a roadway project. Assessing community values generally deals with qualitative issues often explored through interaction with key stakeholders and the community at large. Exhibit 4 5 lists a sample of community value performance measures and provides guidance on their application. Many topics are subjective and are based on the unique definitions provided by stakeholders and the project team. For example, community members may wish to improve “livability” and have corridor specific measures for what it means to them on a particular project. Exhibit 4-4: Cost Performance Measures Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-23 Performance Measure Assessment Techniques and Notes Livability Livability often refers to the quality of life experienced by people who live, work, and recreate in a given place. Transportation infrastructure can positively or negatively affect a community’s livability. Walkability Some communities value the ability for people to easily and comfortably make trips on foot rather than using another mode such as driving. There may be health benefits of living in a walkable community. Arterials designed in a manner to accommodate pedestrians do not create barriers to pedestrian travel. Property Value Roadways have the ability to increase or decrease property value. For example, roadways require right-of-way and increase or restrict access to property; these elements all affect property value. Aesthetics Visually appealing infrastructure can enhance the property value, the viability of businesses, and the desire of people to visit or pass through an area. The appropriate level of aesthetics is determined in part by the location and context of the roadway. Place-making Place-making refers to the creation of focal points and natural gathering places within a community. Elements to the transportation system such as the design of the road network and the streetscape can contribute to place-making. Community Acceptance Transportation projects should generally be accepted by the community before they are built, and projects should not be forced upon unsupportive communities. It may be challenging to gain support for roundabouts in communities unfamiliar with and unfavorable towards them. Special outreach and education may be needed to objectively inform and educate the community and stakeholders about the benefits and tradeoffs of roundabouts. Health Increased active transportation (such as walking and bicycling) may offer a health benefit to a community. Social Equality Transportation projects should reasonably serve the needs of users while avoid ing unreasonable community impacts. Environmental justice is a component of the NEPA process that strives to prevent disproportional impacts to minority groups. Access Multimodal transportation infrastructure can serve a greater segment of the population than a single-mode facility. Some people are unable to drive due to age, disabilities, or other reasons, but are able to walk or use transit. 4.6. OTHER CONSIDERATIONS In addition to the five major groups of performance measures listed above, additional considerations will be relevant on some corridors based upon their location, surrounding land use, and agency specific policies. These other considerations are noted in Exhibit 4 6. Exhibit 4-5: Community Value Considerations

Evaluating the Performance of Corridors with Roundabouts Page A-24 Performance Measure Comments Land-Use Considerations Roadway design choices can influence land-use patterns in a community, and vice versa. A certain alternative may be favorable to a community because it will fit well with existing land-use patterns or it will guide future land use in a manner that is desired. Access- Management Considerations The TRB Access Management Manual (2003) provides additional information on access management considerations and techniques for arterials. Access is generally restricted in the immediate vicinity of a roundabout, and when allowed it may be right-in right-out due to splitter islands. In practice, there is greater variability in access control in the vicinity of signalized intersections. Roundabouts naturally accommodate U-turns, whereas signalized intersections may require special treatments such as jug handles or a wide median. U-turns on multilane streets (both signals and roundabouts) require enough space for drivers to get into the correct lane to make the U-turn maneuver. Economic- Development/Tax- Base Considerations As discussed in Section 4.4, new or improved roadways have the potential to spur economic development and positively influence a community’s tax base. Different project alternatives may have varying degrees of economic impact. Agency Policies Some agencies have policies favoring certain types of roadway or intersection treatments such as non-traversable medians or bicycle lanes. Some agencies have a “roundabouts first” policy. These policies generally require a roundabout (rather than a traffic signal) is constructed at new or rebuilt intersections unless it is demonstrated a roundabout is not feasible. Private Investment and Public-Private Partnerships Some roads, even if they are ultimately turned over to public agencies for ownership, are built with private funds. Private entities contribute funds to road projects that benefit them by improving access or mobility. Roads funded in this manner should meet the needs of investors in addition to meeting the needs of the community-at-large. Legal Issues (including tort) Roundabouts have documented safety benefits of reducing injury and fatal crashes. Roundabouts could be part of a community’s overall risk management approach to asset management. Public Education New or innovative roadway and intersection treatments may be unfamiliar to drivers, and outreach and education may be desirable to improve road safety and their driving experience. Roundabouts are uncommon in some areas, and user education (for each user type) may be beneficial when a community’s first roundabouts are installed. 4.7. EVALUATION TECHNIQUES After the alternatives have been evaluated, a number of methods can be used to compare the evaluations and identify a preferred alternative. Two methods are presented here. 4.7.1. Cost/Benefit Analysis This method compares project costs (initially defined in terms of dollars) to benefits (converted to dollar equivalents from other measures). An alternative in which benefits are greater than costs is typically seen as feasible, and the alternative with the highest ratio of benefits to costs is considered the preferred alternative. This analysis generally encompasses the entire lifecycle of a project. Capital costs are annualized over a period of time, such as 30 years. Some items generally included in a cost/benefit analysis are noted here: Costs: Right-of-way acquisition, capital construction, annual maintenance, electrical consumption. Exhibit 4-6: Other Considerations Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Corridor Comparison Document Page A-25 Benefits: Crash reduction; delay reduction (full day and annual); fuel consumption reduction (full day and annual); emissions reduction; economic benefits to residents, businesses, and the community at large; quality of life improvements. Section 3.7 of NCHRP Report 672 provides additional guidance on computing cost/benefit ratios as well as general information on costs. The construction cost of a roundabout varies greatly, but is generally greater than the cost of a stop controlled intersection. Installation of a signal at an existing intersection typically costs less than construction of a roundabout if no lanes are added. If the installation of a signal requires approach widening, the cost is comparable to a roundabout. The operations and maintenance costs of a roundabout are generally less than a signal (2). 4.7.2. Scoring This method is typically applied by constructing a matrix of all alternatives and all performance measures. Each alternative is given a score for each performance measure. The scores of performance measures can be weighted to account for some being more relevant and important to a given project than others. Summing all scores for each alternative can provide a basis for considering and selecting a preferred alternative. CHAPTER 5: FICTIONAL EXAMPLE APPLICATIONS Four example applications presented in this chapter illustrate the use of the CCD. Each example applies the CCD as an aid in the decision making process. The CCD is not intended to be a standalone document, and practitioners should consult and apply standards and other guidance documents when appropriate. The example applications are: 1. A new suburban greenfield corridor to provide access to undeveloped land and increased connectivity. 2. A community enhancement project on an existing urban corridor. 3. An existing rural corridor in a context sensitive environment beginning to experience suburban development. 4. An existing suburban corridor being evaluated for safety and operational improvements. Although each of the examples listed above includes an aerial photograph of an existing corridor in the United States, they are not intended to portray actual corridors or present factual information. They use fictional street names and present fictional data and findings for the purpose of illustrating the concepts of the CCD.

Evaluating the Performance of Corridors with Roundabouts Page A-26 REFERENCES 1. Transportation Research Board. Highway Capacity Manual 2010. Transportation Research Board of the National Academies, Washington, D.C. 2010. 2. Rodegerdts, L., J. Bansen, C. Tiesler, J. Knudsen, E. Myers, M. Johnson, M. Moule, B. Persaud, C. Lyon, S. Hallmark, H. Isebrands, R. B. Crown, B. Guichet, and A. O’Brien. NCHRP Report 672: Roundabouts: An Informational Guide, 2nd ed. Transportation Research Board of the National Academies, Washington, D.C. 2010. 3. American Association of State Highway and Transportation Officials. Highway Safety Manual.Washington, D.C. 2009. 4. Federal Highway Administration. Signalized Intersections: Informational Guide. Washington, D.C. 2004. 5. American Association of State Highway and Transportation Officials. A Policy on Geometric Design of Highways and Streets.Washington, D.C. 2011. 6. Transportation Research Board. TCRP Report 100: Transit Capacity and Quality of Service Manual. Transportation Research Board of the National Academies, Washington, D.C. 2003. Corridor Comparison Document

Evaluating the Performance of Corridors with Roundabouts Example Application #1 Page A-27 EXAMPLE APPLICATION 1. BEECHMONT AVENUE This fictional example application presents a new suburban roadway built to provide access to land and increased connectivity. Example travel time and crash prediction calculations are presented as well. 1.1. PROJECT INITIATION Steps in the Project Initiation phase of the Project-Planning Process (refer to Corridor Comparison Document, Chapter 3) Cross-Section 4 or 5 lanes (depending on median choice) Travel Lanes 2 each direction Intersection Spacing 1,500 to 2,000 feet Average Daily Traffic (ADT) 26,000 veh/day Peak-Hour Peak Direction Flow 800 to 1,200 veh/h Sidewalks To be provided on each side of roadway Bicycle Lanes None to be provided Local Bus Service None anticipated Land Use Currently rural, suburban development projected 1.1.1. UNDERSTANDING OF CONTEXT Anderson County rezoned the area southwest of the I 32/I 232 interchange to encourage economic development. To provide access to this land, the county is Exhibit 1-1: Key Data

Evaluating the Performance of Corridors with Roundabouts Page A-28 Example Application #1 planning to extend Beechmont Avenue. Beechmont Avenue is a four lane, minor arterial roadway with a posted speed of 45 miles per hour. The current southern terminus of Beechmont Avenue is an interchange at I 32. 125th Street, a gravel roadway, continues south of the interchange for approximately two miles. Plans for Beechmont Avenue call for it to be extended to the south, and then to curve east and tie into the existing I 232/Westgate Boulevard interchange. The county has determined the approximate roadway alignment and is now considering the roadway typical section and intersection control. The county anticipates seven major intersections on Beechmont Avenue, spaced approximately 1500 to 2000 feet apart. The alignment is shown in Exhibit 1 2. Exhibit 1-2: Proposed Corridor Alignment

Evaluating the Performance of Corridors with Roundabouts Example Application #1 Page A-29 1.1.2. USERS AND TRAFFIC VOLUME The forecast ADT on the Beechmont Avenue extension is 26,000. The road is envisioned as a suburban facility serving retail and mid to low density residential development. A low degree of pedestrian and bicycle activity is expected. Forecasts estimate the majority of trips having an origin or destination along the corridor. Intersections serving large commercial or residential developments may experience a high percentage of turning vehicles. For brevity, the fictional example applications only include volumes from one year. Generally, a planning study for a corridor would forecast future, design year volumes, and practitioners would use these volumes for planning and analysis. 1.1.3. PROJECT CATALYST AND GOALS The Beechmont Avenue extension was first proposed eight years ago in Anderson County’s long range transportation plan. The county now has programmed funds for design and construction within the next two years, and planning efforts have intensified. The primary goals of the project are: Provide access to the land surrounding the roadway from both I 32 and I 232, Transport users safely and efficiently, and Create additional network connectivity in the area and provide an alternate to I 32 and I 232 for local trips. 1.1.4. SELECT AND PRIORITIZE PERFORMANCE MEASURES The sections below list the six groups of performance measures discussed in the Corridor Comparison Document (CCD), and identify specific performance measures of importance on the Beechmont Avenue corridor. The performance measures identified below are not necessarily all that could be considered for the Beechmont Avenue project. There are many performance measures that could be used to evaluate a corridor. Some are of critical importance for nearly all corridors (Tier I), and others are only applicable to some corridors (Tiers II and III). For the purpose of illustrating the use of the CCD, this example presents performance measures that are of particular interest on the Beechmont Avenue corridor and help to distinguish the alternatives from one another. This includes Tier I measures like safety and cost, and Tier II and III measures like land use and access. Performance measures of strong interest to the community are generally prioritized over those of lesser interest to the community. 1.1.4.1. Quality of Service Performance Measures Quality of service refers to auto traffic operations and the experience of other corridor users such as pedestrians, bicyclists, and transit riders. Auto traffic operations are generally quantified with the procedures of the Highway Capacity Manual. The quality of service for other users is generally assessed qualitatively or with the multimodal procedures of the Highway Capacity Manual. The Beechmont Avenue extension will be designed to adequately accommodate the forecast traffic volume. Intersections should not experience excessive delay

Evaluating the Performance of Corridors with Roundabouts Page A-30 Example Application #1 for any movement or be close to capacity. The county will assess corridor travel time as well. Key Performance Measures: Arterial capacity; intersection delay, level of service, and volume to capacity ratio; delay to left turn movements; and corridor travel time. 1.1.4.2. Safety Performance Measures The Highway Safety Manual (HSM) provides safety performance functions and crash modification factors to quantify the expected number of crashes or changes in crash frequency associated with different roadway designs. Anderson County recently incorporated the HSM into their project planning process, and assesses the safety performance of any potential alternative. Key Performance Measure: Predicted crash frequency at intersections. 1.1.4.3. Environmental Performance Measures Anderson County completed comprehensive environmental studies for extending Beechmont Avenue several years ago when they selected the roadway’s alignment. In the current phase of this project, there will be minimal environmental regulatory issues to address. However, Anderson County policy requires fuel consumption analysis of new roadway projects. An analysis commensurate with the level of project plans will be performed in accordance with county policy. Key Performance Measure: Fuel consumption. 1.1.4.4. Cost Performance Measures Anderson County performs a cost benefit assessment prior to investing in the final design and construction of a new roadway. The primary components of the analysis typically are construction cost, roadway maintenance costs, cost of delay, cost of crashes, and cost of fuel. The cost benefit assessment is performed over the life cycle of the project. Key Performance Measures: Construction cost, annual maintenance cost, cost of delay experienced by roadway users, costs of injuries and property damage suffered by roadway users, cost of fuel consumed by roadway users. 1.1.4.5. Community Value Performance Measures Stakeholders support extending Beechmont Avenue on the county selected alignment, and have not expressed strong feelings with regard to more detailed aspects of the project such as intersection or roadway cross section design. Anderson County will continue to engage stakeholders throughout the planning process and incorporate their comments and suggestions when feasible. Key Performance Measures: None. 1.1.4.6. Other Performance Measures One goal of the Beechmont Avenue extension is to provide access to undeveloped land. Anderson County will assess the degree to which alternatives provide access to adjacent land while also meeting mobility and safety needs.

Evaluating the Performance of Corridors with Roundabouts Example Application #1 Page A-31 Key Performance Measures: Land access and use. 1.2. CONCEPT DEVELOPMENT Steps in the Concept Development phase of the Project-Planning Process (refer to CCD, Chapter 3) 1.2.1. DEVELOP ALTERNATIVES AND PRELIMINARY OPERATIONS AND SAFETY ANALYSIS Studies on three lane roadways indicate capacities approach 20,000 to 24,000 veh/day. With a forecast average daily traffic (ADT) volume of 26,000 veh/day, Beechmont Avenue will need two lanes in each direction to meet capacity needs. This will result in a four lane or five lane roadway, depending on median choice. Anderson County considered three alternatives for the Beechmont Avenue extension: 1. Alternative #1 is a five lane roadway with a two way left turn lane (TWLTL) and traffic signals at major intersections. 2. Alternative #2 is a four lane roadway with a non traversable median and traffic signals at major intersections. 3. Alternative #3 is a four lane roadway with a non traversable median and roundabouts at major intersections. Signalized alternatives would have left turn lanes on Beechmont Avenue and side street lane needs will be determined on an intersection by intersection basis using forecast peak hour volumes and critical movement analysis. The FHWA publication Signalized Intersections: Informational Guide (2004) provides a methodology for critical movement analysis. Lane needs will be reassessed during the alternatives analysis with a more extensive Highway Capacity Manual methodology based analysis. Roundabouts would have two through lanes on Beechmont Avenue and one or two lanes, as needed, on side street approaches. Anderson County used Exhibit 3 12 of NCHRP Report 672 (reproduced here as Exhibit 1 3) to assess the feasibility of double lane roundabouts on Beechmont Avenue. As shown in Exhibit 1 3, double lane roundabouts are generally sufficient with an ADT of 26,000 and will therefore be sufficient for the traffic volume on Beechmont Avenue.

Evaluating the Performance of Corridors with Roundabouts Page A-32 Example Application #1 The HSM includes methods to predict roadway segment crashes. Generally speaking, the HSM indicates divided roadway segments with raised medians typically have fewer crashes than undivided roadway segments with TWLTLs. Since Alternatives 2 and 3 have a raised median, these alternatives would likely show fewer predicted mid block crashes than Alternative 1. The safety comparison of traffic signals and roundabouts is more complex and is discussed in the Alternatives Analysis section of this example application. 1.2.2. CONCEPTUAL LAYOUTS Anderson County staff developed conceptual layouts of each alternative; the layouts depicted lane needs as determined by the preliminary operations analysis discussed in Section 1.2.1. In addition, the county roundabout concept designs considered principles from NCHRP Report 672 to identify an appropriate inscribed circle diameter, applicable design vehicles, fastest path evaluations, pedestrian and bicycle treatments, good path alignment for multilane entries and exits, and other applicable aspects of contemporary roundabout design. 1.3. ALTERNATIVES ANALYSIS Steps in the Alternatives Analysis phase of the Project-Planning Process (refer to CCD, Chapter 3) Exhibit 1-3: Planning Level Daily Intersection Volumes (Reproduced from NCHRP Report 672)

Evaluating the Performance of Corridors with Roundabouts Example Application #1 Page A-33 1.3.1. EVALUATE THE ALTERNATIVES Exhibit 1 4 summarizes an analysis of the three alternatives proposed for Beechmont Avenue using the key performance measures identified in Section 1.1.4. Perfor- mance Measure Alternative 1 – Signals and TWLTL Alternative 2 – Signals and Median Alternative 3 – Roundabouts Comments Arterial capacity Four- and five-lane signalized arterials generally have a capacity of 40,000 to 50,000 veh/day. This alternative will adequately serve the forecasted 26,000 veh/day. Four- and five-lane signalized arterials generally have a capacity of 40,000 to 50,000 veh/day. This alternative will adequately serve the 26,000 veh/day. Exhibit 1-3 indicates that double-lane roundabouts should adequately serve an ADT of 26,000 veh/day. All alternatives have adequate link capacity. Peak-hour intersec- tion delay and LOS Peak-hour intersection delay will range from 30 to 51 seconds (LOS C or D). Peak-hour intersection delay will range from 31 to 53 seconds (LOS C or D). Peak-hour critical- movement delay will range from 22 to 44 seconds, except at one roundabout where the critical approach will experience 61 seconds of delay. Alternative 3 generally performs the best, with one exception. Intersec- tion v/c ratio Peak-hour v/c ratio will range from 0.64 to 0.81. Peak-hour v/c ratio will range from 0.65 to 0.84. Peak-hour v/c ratio will range from 0.72 to 0.84. In all alternatives, intersections are below capacity. Delay to left-turn move- ments Peak-hour delay for the left-turn movement at most intersections ranges from 40 to 70 seconds. Peak-hour delay for the left-turn movement at most intersections ranges from 40 to 80 seconds. Peak-hour delay for the left-turn movement at most intersections ranges from 15 to 40 seconds. Alternative 3 has the lowest peak-hour left-turn delay. Corridor travel time (See Section 1.3.1.1) The HCM Urban Streets procedure predicts an a.m. peak travel time of 4.0 minutes and a p.m. peak travel time of 4.5 minutes. Corridor travel time will be similar to Alternative 1. Mid- block speeds will increase slightly, and intersection delay will increase slightly due to increased turning volumes. The roundabout corridor travel-time procedure developed as part of NCHRP 03-100 results in a p.m. peak travel time of 5.6 minutes. Alternatives 1 and 2 result in a lower peak travel time. Mid-block safety perfor- mance Conflict points associated with right- and left-turn movements will be present at mid-block driveways. HSM crash modification factors predict a decrease in mid-block crashes of 10% to 20% with a raised median. The mid-block segment speeds are anticipated to be slower compared to Alternatives 1 and 2 and could reduce crash severity and improve the pedestrian’s perceived quality of service. Alternatives 2 and 3 are expected to have better mid-block safety performance than Alternative 1. Exhibit 1-4: Alternatives Analysis

Evaluating the Performance of Corridors with Roundabouts Page A-34 Example Application #1 Perfor- mance Measure Alternative 1 – Signals and TWLTL Alternative 2 – Signals and Median Alternative 3 – Roundabouts Comments Predicted intersec- tion crash frequency (See Section 1.3.1.2) HSM predictive analysis estimates 5.28 auto crashes per year at the northernmost intersection, and similar rates at other intersections. HSM predictive analysis estimates 5.28 auto crashes per year at the northernmost intersection, and similar rates at other intersections. HSM comparative analysis estimates 1.21 to 2.27 auto crashes per year at the northernmost intersection, and similar rates at other intersections. Alternative 3 is expected to have the best intersection safety performance. Estimated construc- tion cost $5.7 million. $6.3 million. $7.2 million. Construction cost ranges from $5.7 to $7.2 million. Annual mainte- nance cost The annual maintenance and power needs for the seven traffic signals is estimated at $35,000. Maintenance costs will be similar to Alternative 1, with the addition of mowing the grass in the median. The annual maintenance cost of the seven roundabouts is estimated at $18,000 and includes maintaining landscaping and pavement markings. The annual maintenance cost of Alternative 3 is approximate- ly half of Alternatives 1 and 2. Annual cost of delay experi- enced by roadway users Drivers will incur an annual cost of $7.6 million per year due to intersection delay. Drivers will incur an annual cost of $7.9 million per year due to intersection delay. Drivers will incur an annual cost of $4.3 million per year due to intersection delay. Alternative 3 has the lowest delay cost. Costs of injuries and property damage suffered by roadway users The estimated cost of crashes at intersections will be $1.5 million per year. The estimated cost of crashes at intersections will be $1.5 million per year. Costs associated with mid-block crashes will be lower than under Alternative 1. The estimated cost of crashes at intersections will be $400,000 per year. The safety cost of Alternative 3 is approximate- ly one-third of Alternatives 1 and 2. Cost of fuel consumed by roadway users Drivers will consume $8.0 million of fuel at intersections. Drivers will consume $8.3 million of fuel at intersections. The median will lengthen some trips compared to Alternative 1 and increase mid-block fuel consumption as well. Drivers will consume $3.8 million of fuel at intersections. The fuel consumption cost of Alternative 3 is approximate- ly half of Alternatives 1 and 2. Land access and use This alternative will provide the highest degree of access. This alternative prohibits left turns into and out of mid- block driveways. Access will be similar to Alternative 2. Roundabouts will allow U-turns. There will be some further restrictions on driveways near intersections. Alternative 1 provides more access than Alternatives 2 and 3. Exhibit 1-4: Alternatives Analysis Con’t

Evaluating the Performance of Corridors with Roundabouts Example Application #1 Page A-35 1.3.1.1. Corridor Travel-Time Analysis Anderson County estimated travel time for Alternative 3 with the procedure illustrated below. The procedure was developed as part of the NCHRP project that produced this CCD. More information on the procedure is found in the main project report. Calculations for the p.m. peak period are shown below. STEP A: GATHER INPUT DATA The sub segment lengths shown in Exhibit 1 5 below were determined based on the conceptual plan in Exhibit 1 2: Roundabout Sub-segment Length (ft) 1 US 800 1 DS 1,140 2 US 1,000 2 DS 940 3 US 800 3 DS 890 4 US 750 4 DS 940 5 US 800 5 DS 1,140 6 US 1,000 6 DS 1,140 7 US 1,000 7 DS 290 The definition of a segment and sub segment is shown in Exhibit 3 4 in the main project report. Exhibit 1 6 lists other data necessary for the travel time analysis. Because this project is at the planning stage, some values are approximated and assumed to be the same for all roundabouts on the corridor. Variable Value Unit Notes Posted speed limit (SL) 45 mph Planned speed limit for Beechmont Avenue Volume-to-capacity (v/c) ratio 0.78 none The average of the range of v/c based on preliminary traffic analysis Circulating speed (SL) 20 mph Typical 2 fastest-path speed for a double-laneR roundabout Peak-hour directional entry flow 1,000 vph The average of the range of flow in the corridor traffic projections Inscribed circle diameter (ICD) 160 feet Typical value for a roundabout with two circulating lanes Central island diameter (CID) 100 feet Typical value for a roundabout with two circulating lanes Exhibit 1-5: Segment Lengths Exhibit 1-6: Data for Analysis

Evaluating the Performance of Corridors with Roundabouts Page A-36 Example Application #1 STEP B: DETERMINE FREE FLOW SPEED Initially assume the roundabout influence areas of adjacent roundabouts do not overlap. This assumption is checked in Step D, and addressed in Step E if it proves to be incorrect. The free flow speed over each segment can be estimated using the free flow speed models: Sf,US = 15.1 + 0.0037*L + 0.43 * SL + 0.05 * CID – 4.73 * OL Sf,DS = 14.6 + 0.0039*L + 0.48 * SL + 0.02 * CID – 4.43 * OL where Sf,US = upstream free flow speed (mph); Sf,DS = downstream free flow speed (mph); L = sub segment length (feet); SL = posted speed limit (mph); CID = central island diameter (feet); and OL = binary variable equal to one when overlapping influence areas are present on the sub segment, zero otherwise. The results are shown in Exhibit 1 7: Roundabout Sub-segment Free-Flow Speed (mph) 1 US 42.4 1 DS 42.6 2 US 43.2 2 DS 41.9 3 US 42.4 3 DS 41.7 4 US 42.2 4 DS 41.9 5 US 42.4 5 DS 42.6 6 US 43.2 6 DS 42.6 7 US 43.2 7 DS 39.3 For example, the free flow speed for sub segment 1US can be computed using the free flow speed model for an upstream sub segment: Exhibit 1-7: Free-Flow Speed Results

Evaluating the Performance of Corridors with Roundabouts Example Application #1 Page A-37 = 42.41 mph Using the downstream sub segment free flow speed model, the estimated FFS for sub segment 1DS follows as: = 42.646 mph STEP C: DETERMINE ROUNDABOUT INFLUENCE AREA LENGTH The length of each roundabout influence area can be estimated using the roundabout influence area models: RIAUS = 165.9 + 13.8* Sf – 21.1*Sc RIADS = 149.8 + 31.4* Sf – 22.5*Sc where RIAUS = upstream roundabout influence area length (feet); RIADS = downstream roundabout influence area length (feet); and Sc = circulating speed (mph). The resulting lengths are shown in Exhibit 1 8. The above values are shown rounded in Exhibit 1-7. However, unrounded values for these and other intermediate calculations should be used for subsequent calculations.

Evaluating the Performance of Corridors with Roundabouts Page A-38 Example Application #1 Roundabout Sub- segment Roundabout Influence Area Length (feet) 1 US 329 1 DS 739 2 US 339 2 DS 715 3 US 329 3 DS 709 4 US 327 4 DS 715 5 US 329 5 DS 739 6 US 339 6 DS 739 7 US 339 7 DS 496 For example, the roundabout influence area of sub segment 1US can be calculated using the roundabout influence area model for an upstream sub segment: = 329 feet The roundabout influence area of sub segment 1DS can be calculated using the roundabout influence area model for a downstream sub segment: = 739 feet STEP D: CHECK OVERLAPPING ROUNDABOUT INFLUENCE AREAS Step B assumed roundabout influence areas did not overlap. To check this assumption, compare the roundabout sub segment lengths in Exhibit 1 5 to the roundabout influence areas calculated in Step C and listed in Exhibit 1 8. All sub segments except for one (7DS) are longer than their respective roundabout influence areas and do not overlap. The one overlapping sub segment—7DS—is not a true example of two sub segments having overlapping influence areas because it lies beyond the last roundabout on the corridor. However, because the roundabout influence area is still longer than the sub segment, it is considered to “overlap” and free flow speed is recalculated in the next step. Exhibit 1-8: Roundabout Influence Area Results

Evaluating the Performance of Corridors with Roundabouts Example Application #1 Page A-39 STEP E: RECALCULATE FREE FLOW SPEED OF SEGMENTS WITH OVERLAPPING ROUNDABOUT INFLUENCE AREAS Treating sub segment 7DS with OL = 1, the free flow speed is now 34.9 mph. STEP F: SELECT CONTROLLING FREE FLOW SPEED FROM EACH PAIR OF SUB SEGMENTS This step takes the minimum free flow speed within each pair of sub segments for use in future calculations. For example, sub segment 1DS has a free flow speed of 42.6 mph, and sub segment 2US has a free flow speed of 43.2 mph, so the controlling free flow speed for segment 1DS/2US is 42.6 mph. STEP G: DETERMINE SEGMENT RUNNING TIME Referring to Equation 17 6 from the HCM 2010 (Step 2 of Chapter 17), the running times are calculated for each segment, as shown in Exhibit 1 9: Roundabout Sub- segment Proximity Adjustment Factor Sub- segment Running Time (s) 1 US 1.027 14.6 1 DS 1.026 19.7 2 US 1.026 17.5 2 DS 1.027 16.9 3 US 1.027 14.7 3 DS 1.027 16.2 4 US 1.027 14.1 4 DS 1.027 16.9 5 US 1.027 14.7 5 DS 1.026 19.7 6 US 1.026 17.5 6 DS 1.026 19.7 7 US 1.026 17.5 7 DS 1.033 9.6 This process also requires the computation of the proximity adjustment factor (HCM 2010 Equation 17 5). Due to the access management policy associated with the context of the site development, all midsegment access point delays on Beechmont Avenue were assumed to be zero. Exhibit 1-9: Segment Running Time Results

Evaluating the Performance of Corridors with Roundabouts Page A-40 Example Application #1 STEP H: DETERMINE GEOMETRIC DELAY OF EACH SUB SEGMENT Using these controlling free flow speeds, the geometric delay incurred over the roundabout influence area can be estimated for each segment using the following model: Delaygeom, US= 1.57 + 0.11*Sf– 0.21*Sc Delaygeom, DS = 2.63 + 0.09*Sf + 0.73 * ICD * (1/Sc 1/Sf) where Delaygeom, US = upstream geometric delay (seconds); and Delaygeom, DS = downstream geometric delay (seconds). The resulting geometric delays are shown in Exhibit 1 10: Roundabout Sub- segment Geometric Delay (s) 1 US 2.0 1 DS 4.2 2 US 2.1 2 DS 4.1 3 US 2.0 3 DS 4.1 4 US 2.0 4 DS 4.1 5 US 2.0 5 DS 4.2 6 US 2.1 6 DS 4.2 7 US 2.1 7 DS 2.9 For example, the geometric delay of sub segment 1US can be calculated using the geometric delay model for an upstream sub segment: = 2.0 seconds The geometric delay of sub segment 1DS can be calculated using the geometric delay model for a downstream sub segment: Exhibit 1-10: Geometric Delay Results

Evaluating the Performance of Corridors with Roundabouts Example Application #1 Page A-41 = 4.2 seconds STEP I: DETERMINE IMPEDED DELAY OF EACH SUB SEGMENT Using the controlling free flow speeds and traffic characteristics, impeded delay (i.e., the delay incurred due to traffic conditions and not geometric constraints) of each sub segment is now calculated. The following are the impeded delay models: Delayimp, US = 5.35 + 0.15*Sf+ 42.50*x – 0.03 * ventering Delayimp, DS = 2.65 + 0.07*Sf+ 3.10*x + 0.0020 *L – 0.0010 *Lmedian + 0.0014 * Lcurb where x = volume to capacity ratio; ventering = entering flow (vph); Lmedian = length of sub segment with restrictive median (feet); and Lcurb = length of sub segment with curb (feet). The results are shown in Exhibit 1 11: Roundabout Sub- segment Impeded Delay (s) 1 US 4.2 1 DS 5.5 2 US 4.1 2 DS 5.0 3 US 4.1 3 DS 4.8 4 US 4.1 4 DS 5.0 5 US 4.2 5 DS 5.5 6 US 4.2 6 DS 5.5 7 US 3.0 7 DS 2.9 Exhibit 1-11: Impeded Delay Results

Evaluating the Performance of Corridors with Roundabouts Page A-42 Example Application #1 For example, the impeded delay of sub segment 1US can be calculated using the impeded delay model for an upstream sub segment: = 4.2 seconds The impeded delay of sub segment 1DS can be calculated using the impeded delay model for a downstream sub segment: = 5.5 seconds STEP J: AGGREGATE SUB SEGMENT PERFORMANCE MEASURES TO CHAPTER 17 SEGMENT LEVEL The average travel time over each segment is calculated by adding the following elements of each (non overlapping) sub segment: 1. The sub segment running time, 2. The geometric delay, and 3. The impeded delay. Exhibit 1 12 displays the average travel time for each segment, as well as a list of the sub segments that comprise each segment: Segment Sub-segments Aggregated to Comprise Segment Average Travel Time (s) Downstream Upstream A N/A 1US 20.8 B 1DS 2US 53.2 C 2DS 3US 46.7 D 3DS 4US 45.2 E 4DS 5US 46.7 F 5DS 6US 53.2 G 6DS 7US 53.2 H 7DS N/A 15.5 For example, the average travel time of Segment A is 14.6 seconds (sub segment 1US running time) + 2.0 seconds (sub segment 1US geometric delay) + 4.2 seconds (sub segment 1US impeded delay) = 20.8 seconds STEP K: DETERMINE SEGMENT AVERAGE TRAVEL SPEED Exhibit 1-12: Average Travel Time for Each Segment

Evaluating the Performance of Corridors with Roundabouts Example Application #1 Page A-43 After the travel times are computed, the average segment travel speed is computed by dividing each segment length by the respective average travel time. This performance measure is consistent with the methodology in HCM Chapter 17. The results are shown in Exhibit 1 13: Segment Average Travel Time (s) Segment Length (ft) Average Travel Speed (mph) A 20.8 800 26.2 B 53.2 2,140 27.4 C 46.7 1,740 25.4 D 45.2 1,640 24.7 E 46.7 1,740 25.4 F 53.2 2,140 27.4 G 53.2 2,140 27.4 H 15.5 290 12.8 For example, the average travel speed of Segment A is computed using the segment length (800 feet): = 26.2 mph STEP L: DETERMINE SEGMENT LEVEL OF SERVICE Referring to Exhibit 17 2 in the HCM, the level of service can then be computed for each segment using the percentage of the base FFS at which the segment operates. The results are shown in Exhibit 1 14: Segment Average Travel Speed (mph) Base Free-Flow Speed (mph) Travel Speed as a Percentage of Base Free-Flow Speed LOS A 26.2 42.4 61.8 C B 27.4 42.6 64.4 C C 25.4 41.9 60.6 C D 24.7 41.7 59.3 C E 25.4 41.9 60.6 C F 27.4 42.6 64.4 C G 27.4 42.6 64.4 C H 12.8 39.3 32.5 E The results indicate all but one segment (the short Segment H at the end of the route) operate at LOS C. The final segment, Segment H, operates at LOS E, likely Exhibit 1-13: Average Travel Speed for Each Segment Exhibit 1-14: Level of Service for Each Segment

Evaluating the Performance of Corridors with Roundabouts Page A-44 Example Application #1 because the entire segment lies within the influence area of Roundabout 7; i.e., vehicles are accelerating or decelerating over the entire sub segment. FACILITY LEVEL OF SERVICE To aggregate the travel times over the entire facility, HCM Chapter 16 is used directly. The facility travel speed is the aggregation of all segment travel speeds. The facility base FFS is the aggregation of all segment FFS. For Beechmont Avenue, the travel speed is 25.8 mph and the facility base FFS is 42.4 mph. Per Exhibit 16 4 of the HCM 2010, the facility operates at LOS C. 1.3.1.2. Predicted Intersection Crash Frequency Anderson County assessed intersection traffic safety using the crash prediction method from the HSM. The crash prediction method estimates the number of crashes that could be expected as a function of geometry and ADT. The northernmost intersection on the Beechmont Avenue extension was selected to demonstrate the procedure and potential results for each alternative. Basic assumptions used in the analysis and the calculations are summarized below. ALTERNATIVES 1 AND 2 CRASH PREDICTION Conditions: Four lane, divided major road Two lane, divided minor road One left turn lane on each major road approach Protected/permi’ed left turn signal phasing on major road Design AADT of major road is 26,000 vehicles/day Design AADT of minor road is 7,000 vehicles/day Lighting is present Suburban environment No available estimate of pedestrian or bicycle volume Calculations: Chapter 12 in Part C of the HSM provides Safety Performance Functions for segments and intersections on urban and suburban arterial highways. The intersection crash prediction models are presented below for single and multiple vehicle crashes. Vehicle pedestrian and vehicle bicycle crashes are assumed to be negligible. Safety Performance Functions (SPFs): SPF for multiple vehicle crashes at the intersection (Equation 12 21): Nbimv = exp( 10.99 + 1.07 * ln(26,000) + 0.23 * ln(7,000)) = 6.845 SPF for single vehicle crashes at the intersection (Equation 12 24): Nbisv = exp( 10.21 + 0.68 * ln(26,000) + 0.27 * ln(7,000)) = 0.404

Evaluating the Performance of Corridors with Roundabouts Example Application #1 Page A-45 Additional equations are provided in the HSM for determining the proportion of total crashes that are Fatal and Injury (FI) crashes and Property Damage–Only (PDO) crashes. Anderson County’s safety policy is more focused on total crashes than specific severities of crashes, so the additional calculations are omitted here for brevity. The base conditions of the SPF assume no turn lanes and permitted left turn phasing, permitted right turn on red, no lighting, and no red light cameras. To account for site specific variations from these base conditions, Crash Modification Factors must be applied as multiplicative factors to the predicted number of crashes. Crash Modification Factors (CMFs): o Left turn lanes on major approaches: 0.81 (Table 12 24) o Protected/permitted phasing on major approaches: 0.99 (Table 12 25) o Lighting: 0.91 (Equation 12 36 and Table 12 27) Calculate Predicted Average Crash Frequency: Npredicted int = (6.845 + 0.404) * 0.81 * 0.99 * 0.91 = 5.28 auto crashes per year. (Some additional, pedestrian and bicycle crashes may occur, but this cannot be predicted without pedestrian and bicycle volumes.) ALTERNATIVE 3 PREDICTED CHANGE IN CRASHES Part C of the HSM does not contain SPFs for roundabouts, but Part D contains CMFs for converting various traditional intersection forms into roundabouts (these CMFs also appear in NCHRP Report 672). CMFs for converting signalized intersections to roundabouts are found in Table 14 3 of the HSM, reproduced here in Exhibit 1 15: Exhibit 1-15: CMFs for Signal to Roundabout Conversion (Reproduced from HSM)

Evaluating the Performance of Corridors with Roundabouts Page A-46 Example Application #1 As shown in Exhibit 1 15, the CMF for converting a suburban signalized intersection to a two lane roundabout is 0.33, with a standard error of 0.05. With 95% confidence, the crashes are reduced by a factor of: 0.33 ± (2 *0.05) = 0.23 – 0.43 Therefore, if Beechmont Avenue is constructed with roundabouts (Alternative 3): 5.28 * 0.23 to 5.28 * 0.43 = 1.21 to 2.27 auto crashes per year are expected. 1.3.2. IDENTIFY PREFERRED ALTERNATIVE All alternatives provide adequate capacity and generally operate acceptably under design year traffic forecasts. Construction cost estimates range from $5.7 to $7.2 million. There was initially disagreement among Anderson County staff regarding alternatives. Drivers will experience longer travel times with Alternative 3 than they would with Alternatives 1 or 2 because of the geometric delay associated with the roundabouts. However, the HSM estimates roundabouts will have approximately one third the number of crashes that signalized intersections on Beechmont Avenue would have, and the corresponding (safety related) economic cost borne by drivers would be several times higher with signalized intersections than with roundabouts. Anderson County ultimately selected Alternative 3 (roundabouts). Safety performance played a large role in the decision. It was agreed travel time should be of lesser importance on this corridor given that the primary function of the Beechmont Avenue extension is to increase access to land, not provide mobility through the area.

Evaluating the Performance of Corridors with Roundabouts Example Application #2 Page A-47 EXAMPLE APPLICATION 2. OCEAN DRIVE This fictional example application presents a community enhancement project on an urban corridor. 2.1. PROJECT INITIATION Steps in the Project Initiation phase of the Project-Planning Process (refer to Corridor Comparison Document, Chapter 3) Cross-Section 5 lanes plus parallel parking on both sides Travel Lanes 2 each direction. The 5th lane is a two-way left-turn lane Intersection Spacing 600 to 800 feet ADT 16,000 veh/day Peak-Hour Peak-Direction Flow 600 to 750 veh/h 85th Percentile Speed 40 mph Existing Control 2 signals, 3 TWSC Peak-Hour Pedestrian Volume Along Ocean Drive 50 to 100 p/h Peak-Hour Pedestrian Volume Crossing Ocean Drive 35 to 80 p/h per intersection Sidewalks Present on both sides Bicycle Lanes None Local Bus Service 15 minute headways Land Use Dense Residential/Commercial Exhibit 2-1: Key Data

Evaluating the Performance of Corridors with Roundabouts Page A-48 Example Application #2 2.1.1. UNDERSTANDING OF CONTEXT Ocean Drive is a five lane roadway with two travel lanes in each direction, a two way left turn lane, and parallel on street parking. The surrounding road network is a grid, and the ocean is two blocks west of the corridor. Beyond the roadway are sidewalks and businesses that primarily front the sidewalk directly. Some businesses with parking lots and residential units are located along the corridor. In the neighborhood surrounding Ocean Drive, development consists primarily of single family housing, with some multifamily housing. The intersections at Atlantic Street, Arctic Street, and Southern Street are two way stop controlled, and the intersections at Indian Street and Pacific Street are signalized. The intersections are between 600 and 800 feet apart. The corridor is illustrated in Exhibit 2 2. (stop sign symbols indicate two way stop control) 2.1.2. USERS AND TRAFFIC VOLUME Ocean Drive serves a variety of users. The ADT is 16,000 veh/day, and peak hour, peak direction flows range from 600 to 750 veh/h. The 85th percentile Exhibit 2-2: Existing Corridor

Evaluating the Performance of Corridors with Roundabouts Example Application #2 Page A-49 speeds along Ocean Drive are approximately 40 miles per hour. There is relatively lile east west traffic crossing the corridor. Peak hour, bi directional, cross street volumes range from 50 to 100 vehicles per hour. The majority of vehicles on Ocean Drive have an origin or destination located within several miles of the project area; longer distance traffic primarily uses a freeway located several miles inland. Crash rates on Ocean Drive over the past five years are below the state average for similar facilities. Pedestrian volumes along Ocean Drive range from 50 to 100 persons during the peak hour. Pedestrian volumes crossing Ocean Drive at each intersection range from 35 to 80 persons during the peak hour. No bicycle counts are available. Observed bicycle activity suggests the majority of cyclists travelling through the area avoid Ocean Drive and instead ride on the streets one block to the east or west. Anecdotal evidence suggests riders are most comfortable travelling on these streets. Local bus service operates on Ocean Drive with 15 minute headways. For brevity, the fictional example applications only include volumes from one year. Generally, a planning study for a corridor would forecast future, design year volumes and practitioners would use these volumes for planning and analysis. 2.1.3. PROJECT CATALYST AND GOALS Members of the community expressed a desire to improve the walkability and create a business friendly atmosphere on Ocean Drive. Traffic speeds and the width of the roadway—approximately 70 feet curb to curb—make it difficult for pedestrians to cross Ocean Drive. Many businesses along the corridor lack parking lots and are patronized by area residents who walk to them or drivers who park on the street. Business owners state the limited on street parking and poor pedestrian atmosphere of the corridor are negatively impacting their customer base. The owners have worked with the local community association to encourage the city to change the roadway to a slower speed facility with a pedestrian friendly configuration. The primary goals of the project are to: Improve walking and bicycling conditions, Increase the supply of on street parking, and Maintain acceptable auto operations. 2.1.4. SELECT AND PRIORITIZE PERFORMANCE MEASURES The sections below list the six groups of performance measures discussed in the CCD, and identify specific performance measures of importance on the Ocean Drive corridor. The performance measures identified below are not necessarily all that could be considered for the Ocean Drive project. There are many performance measures that could be used to evaluate a corridor. Some are of critical importance for nearly all corridors (Tier I), and others are only applicable to some corridors (Tiers II and III). For the purpose of illustrating the use of the CCD, this example presents performance measures that are of particular interest on the Ocean Drive corridor and help to distinguish the alternatives from one another. This includes Tier I measures like intersection level of service and cost,

Evaluating the Performance of Corridors with Roundabouts Page A-50 Example Application #2 and Tier II and III measures like crosswalk length and aesthetics. Performance measures of strong interest to the community are generally prioritized over those of lesser interest to the community. 2.1.4.1. Quality of Service Performance Measures Quality of service refers to auto traffic operations and the experience of other corridor users such as pedestrians, bicyclists, and transit riders. Auto traffic operations are generally quantified with the procedures of the Highway Capacity Manual. The quality of service for other users is generally assessed qualitatively or with the multimodal procedures of the Highway Capacity Manual. Traditional auto performance measures, such as intersection delay, volume to capacity ratio, and corridor travel time, should be considered in the Ocean Drive study to assess the potential for congestion. Additionally, some of the two way stop controlled streets currently experience high delay for the left turn movement onto Ocean Drive. Side street delay should also be considered. Collectively, pedestrians, bicyclists, and bus riders account for 20 to 30 percent of the peak hour trips along Ocean Drive. The current roadway is difficult for pedestrians to cross due to its width and the speed of traffic. The alternatives analysis should assess the length of the pedestrian crossings and the speed of vehicles on Ocean Drive. Roundabout influence area, a component of the roundabout corridor travel time procedure developed as part of this NCHRP project, is used to estimate the extents of the corridor over which travel speeds are lowered due to roundabouts. Key Performance Measures: Crosswalk length, traffic speed, peak hour intersection level of service, intersection v/c ratio, auto delay for minor street left turn movements. 2.1.4.2. Safety Performance Measures Improving pedestrian and bicycle quality of experience is a goal of this project. Although the transportation profession generally lacks tools for quantitatively assessing pedestrian and bicycle safety, a number of surrogate safety measures can be considered. In the case of Ocean Drive, the community identified the roadway crossing distance and high traffic speeds—especially at two way stop controlled intersections—as challenges to pedestrians. Improvements in these elements can be considered as surrogates for pedestrian safety when evaluating alternatives. Key Performance Measures: Crosswalk length (covered under traffic operations), traffic speed (covered under traffic operations), bicyclist comfort. 2.1.4.3. Environmental Performance Measures This project will modify existing roadways in a developed urban area. No undeveloped land will be disturbed, and nearly all work for any of the alternatives would occur within the existing right of way. There are several parks and schools in the project area away from Ocean Drive. It is unlikely these facilities will be impacted. Key Performance Measures: None.

Evaluating the Performance of Corridors with Roundabouts Example Application #2 Page A-51 2.1.4.4. Cost Performance Measures Any build alternative will have capital construction and annual maintenance costs. Business and community associations indicated they will contribute to some maintenance needs such as landscaping and sidewalk cleaning. The anticipated impact on businesses in the corridor, including their profits and their impact on the tax base, is another cost to consider in the alternatives analysis. Key Performance Measures: Construction cost, anticipated impact on businesses. 2.1.4.5. Community Value Performance Measures The study of Ocean Drive began at the request of community members; therefore, an alternative should only be selected if it is embraced by the community. The community is particularly concerned about the pedestrian environment and the image of the corridor. Some property owners, particularly business owners, have a strong interest in preserving or increasing property values. Key Performance Measures: Walkability, property value, aesthetics, community acceptance. 2.1.4.6. Other Performance Measures On street parking on Ocean Drive is highly used at certain times of the day, making it difficult for customers and residents to find open parking spaces. Key Performance Measure: Parking supply. 2.2. CONCEPT DEVELOPMENT Steps in the Concept Development phase of the Project-Planning Process (refer to Corridor Comparison Document, Chapter 3) 2.2.1. DEVELOP ALTERNATIVES AND PRELIMINARY OPERATIONS ANALYSIS Exhibit 2 3 illustrates the iterative process of developing alternatives and conducting the preliminary operations analysis as it occurred on the Ocean Drive project.

Evaluating the Performance of Corridors with Roundabouts Page A-52 Example Application #2 2.2.1.1. Brainstorming of Strategies The community engagement process resulted in several strategies for achieving project goals: Road diet: Reduce the number of lanes on Ocean Drive, add bike lanes, potentially widen sidewalks, potentially narrow travel lanes. Couplet: Convert Ocean Drive to one way (direction to be determined), and divert traffic travelling in the other direction to a parallel roadway. Traffic signals: Convert the three unsignalized major intersections along Ocean Drive to signal control. Roundabouts: Convert the five major intersections along Ocean Drive to roundabouts. These strategies are commonly used tools a practitioner could consider to achieve project goals. They are not alternatives in the sense that each one is not necessarily a complete solution, and they may be combined in various ways. For example, a road diet could use traffic signals or roundabouts at intersections, or Ocean Drive could be converted to one way with additional traffic signals. Prior to developing alternatives, city engineers assessed the viability of additional traffic signals or roundabouts on Ocean Drive using traffic volumes. Exhibit 2-3: Iterative Process of Developing Alternatives and Conducting Preliminary Operations Analysis

Evaluating the Performance of Corridors with Roundabouts Example Application #2 Page A-53 2.2.1.2. Preliminary Operations Analysis Road Diet Strategy: The ADT of Ocean Drive is 16,000 veh/day. Other two lane roadways in the city have an ADT greater than 20,000 veh/day and do not experience degraded operations. Based upon ADT, a road diet may be feasible on Ocean Drive. Couplet Strategy: Streets one block to the east and to the west of Ocean Drive have a curb to curb width of 50 to 65 feet and a number of connections with Ocean Drive via the street grid. Converting a parallel street to carry one direction of Ocean Drive’s traffic may be feasible. Traffic Signal Strategy: Based upon peak hour turning movement counts, none of the unsignalized intersections meet the MUTCD’s peak hour signal warrant. Additionally, if peak hour volumes were consistent for four or eight hours, they would not satisfy the four hour vehicular volume or the eight hour vehicular volume warrants. Hourly volumes over the course of four or eight hours will actually be lower than peak hour volumes, indicating that these warrants are not satisfied. The most recent pedestrian counts, although several years old, indicate the pedestrian volume warrant is not met. Therefore, the city determined it was not feasible to add traffic signals at each intersection on Ocean Drive and no alternatives will include this strategy. Exhibits 2 4, 2 5, and 2 6 present the signal warrant analysis for Atlantic Street, the highest volume TWSC intersection on the corridor. In Exhibits 2 4 and 2 5, note that the minor street volume (shown on the y axis) does not meet the minimum value of 100 vehicles per hour (Exhibit 2 4) or 80 vehicles per hour (Exhibit 2 5), so no analysis of the major street volume is necessary. Exhibit 2-4: Analysis of Peak- Hour Vehicular Volume Signal Warrant at Highest-Volume Intersection Under Road Diet Concept (reproduced from 2009 MUTCD Figure 4C-3)

Evaluating the Performance of Corridors with Roundabouts Page A-54 Example Application #2 Roundabout Strategy: City engineers evaluated the geometric and operational feasibility of roundabouts. Exhibit 2 7 presents the available right of way at an intersection along Ocean Drive. Constraints at other intersections are similar. Exhibit 2-5: Analysis of Four-Hour Vehicular Volume Signal Warrant at Highest-Volume Intersection Under Road Diet Concept (reproduced from 2009 MUTCD Figure 4C-1) Exhibit 2-6: Analysis of Eight-Hour Vehicular Volume Signal Warrant at Highest-Volume Intersection Under Road Diet Concept (reproduced from 2009 MUTCD Table 4C-1)

Evaluating the Performance of Corridors with Roundabouts Example Application #2 Page A-55 The 125 foot dimension depicted in Exhibit 2 7 would accommodate an inscribed circle diameter (ICD) of approximately 110 feet, plus sidewalks beyond the roundabout. Guidance in NCHRP Report 672 identifies the common range of single lane roundabout ICDs as 90 to 180 feet depending on the design vehicle. A roundabout with a 110 ft ICD will generally accommodate a city bus. The diameter would need to be increased to accommodate a truck such as a WB 67. City engineers determined a single lane roundabout is potentially geometrically feasible, and larger trucks such as WB 67s, which are uncommon on Ocean Drive, can be directed to parallel streets. To assess the operational feasibility of single lane roundabouts, city engineers used Exhibit 3 14 of NCHRP Report 672 (reproduced here as Exhibit 2 8). Total entering peak hour volumes at each intersection range from 1,000 to 1,100 veh/h, with the majority of traffic making through movements on Ocean Drive. Therefore, single lane roundabouts may be operationally feasible, but a more detailed analysis should be conducted to confirm this. Multilane entry configuration would require a larger ICD. The larger ICD would require acquiring buildings, which is not considered feasible on this corridor. Exhibit 2-7: Available Distance Between Buildings at a Typical Intersection on Ocean Drive

Evaluating the Performance of Corridors with Roundabouts Page A-56 Example Application #2 2.2.1.3. Initial Layouts Based on the initial operational analysis of the strategies, the city developed three concepts for corridor improvements: 1. Alternative #1 is a road diet converting Ocean Drive from a five lane section to a three lane section. The two way left turn lane and one travel lane in each direction are preserved, bicycle lanes are added, and, on some blocks, parallel parking is converted to angle parking. Intersection control remains the same as existing conditions (see Exhibit 2 2). 2. Alternative #2 creates a one way couplet. Palm Drive, located one block east of Ocean Drive, is converted to one way northbound with two travel lanes and on street parking on both sides of the street. Ocean Drive is converted to two southbound travel lanes, and a curb separated parking area provides angle and parallel parking. Northbound traffic is transitioned to and from Ocean Drive one to two blocks north and south of the study area where connections already exist. Control on Ocean Drive remains the same as existing conditions (see Exhibit 2 2). Control on Palm Drive will be determined at a later stage of the planning process. 3. Alternative #3 is a road diet adding roundabouts at each of the five intersections in the Ocean Drive study area. Ocean Drive is reduced to one travel lane in each direction, a median is added, bicycle lanes are added, and some parallel parking is converted to angle parking. 2.2.1.4. Additional Preliminary Operations Analysis While considering the corridor strategies, two potential operational issues became apparent with the one way couplet: With increased traffic on Palm Drive, it may be appropriate to convert the AWSC intersections on Palm Drive to TWSC. Exhibit 2-8: Planning- Level Analysis of Roundabout Lane Needs (reproduced from NCHRP Report 672 Exhibit 3-14)

Evaluating the Performance of Corridors with Roundabouts Example Application #2 Page A-57 Detailed analysis of the operations and geometrics at the northern and southern ends of the couplet will be needed. At the southern end, Palm Drive will need to be connected to the Ocean Drive/Coconut Lane intersection, and the intersection will need to be reconfigured. At the northern end, the transition of northbound traffic back to Ocean Drive via Atlantic Street should be studied. These issues are site specific and cannot be assessed with a “rule of thumb” or planning level analysis. The city decided to retain the couplet strategy (as Alternative 2) and explore the issues as part of the alternatives analysis. 2.2.2. CONCEPTUAL LAYOUTS Exhibits 2 9 through 2 11 depict the conceptual layouts of the three alternatives.

Evaluating the Performance of Corridors with Roundabouts Page A-58 Example Application #2 Exhibit 2-9: Typical Ocean Drive Intersection and Road Segment, Alternative 1

Evaluating the Performance of Corridors with Roundabouts Example Application #2 Page A-59 Exhibit 2-10A: Alternative 2 Overview

Evaluating the Performance of Corridors with Roundabouts Page A-60 Example Application #2 Exhibit 2-10B: Typical Ocean Drive Intersection and Road Segment, Alternative 2

Evaluating the Performance of Corridors with Roundabouts Example Application #2 Page A-61 Exhibit 2-11: Typical Ocean Drive Intersection and Road Segment, Alternative 3

Evaluating the Performance of Corridors with Roundabouts Page A-62 Example Application #2 2.3. ALTERNATIVES ANALYSIS Steps in the Alternatives Analysis phase of the Project-Planning Process (refer to Corridor Comparison Document, Chapter 3) 2.3.1. EVALUATE THE ALTERNATIVES Exhibit 2 12 summarizes an analysis of the three alternatives proposed for Ocean Drive using the key performance measures identified in Section 2.1.4. Perfor- mance Measure Alternative 1 – Road Diet with Signals and TWSC Alternative 2 – One-Way Couplet with Signals and TWSC Alternative 3 – Road Diet with Roundabouts Comments Crosswalk length The number of lanes being crossed decreases, and the overall crossing distance may decrease if curb extensions are used. Pedestrians will cross one direction of traffic and two travel lanes. The entrances and exits to the median- separated parking areas may be confusing and challenging to pedestrians. Crossings will become two-stage; each stage will only cross one lane of traffic. Each alternative appears to address this performance measure. Traffic speed (see Section 2.3.1.1) Reducing travel lanes may slow traffic by changing the character of the roadway and increasing the density of traffic. However, there are no geometric features that reinforce the desired speed reduction. This design may increase the speed of traffic by physically separating on-street parking from the travel lanes on Ocean Drive. Speeds may increase on Palm Drive as it becomes a higher-order roadway and some AWSC intersections become TWSC. Roundabouts slow drivers to 25 mph or less at every intersection. The roundabouts are 600 to 800 feet apart, and roundabout influence areas are nearly this long. Roundabouts will reduce speeds on most of the corridor. Calculations for roundabout influence area lengths are shown in Section 2.3.1.1. Roundabouts appear to provide the best speed management technique, followed by the road diet. The couplet may potentially be worse than existing conditions. Exhibit 2-12: Alternatives Analysis

Evaluating the Performance of Corridors with Roundabouts Example Application #2 Page A-63 Perfor- mance Measure Alternative 1 – Road Diet with Signals and TWSC Alternative 2 – One-Way Couplet with Signals and TWSC Alternative 3 – Road Diet with Roundabouts Comments Peak-hour intersec- tion LOS During the a.m. and p.m. peak hours, the two signalized intersections will operate at LOS A or B and the TWSC intersections will operate at C, D, or E. Ocean Drive/Atlantic Street operates at LOS E during the p.m. peak hour. Existing signals and stop-control were left in place. During the a.m. and p.m. peak hours, the two signalized intersections will operate at LOS A or B and the TWSC intersections will operate at LOS B or C. Analysis assumed AWSC intersections on Palm Drive are converted to TWSC, the left turn from Palm Drive to Atlantic Street is uncontrolled, and existing signals and stop-control were left in place on Ocean Drive. During the a.m. and p.m. peak hours, the roundabouts will operate at LOS B or C. Each concept performs acceptably during the peak hours. Roundabouts may offer less delay during non- peak conditions compared to the other concepts. Intersec- tion v/c ratio During the a.m. and p.m. peak hours, the v/c of the intersections (TWSC and signalized) will be 0.64 or less. Same assumptions as “Delay & LOS.” During the a.m. and p.m. peak hours, the v/c of the intersections (TWSC and signalized) will be 0.48 or less. Same assumptions as “Delay & LOS.” During the a.m. and p.m. peak hours, the v/c of the roundabouts will range from 0.52 to 0.74. Each concept performs acceptably. The couplet has lower v/c ratios than the other concepts. Minor- street left- turn delay During the a.m. and p.m. peak hours, the minor-street left-turn delay will be 38 seconds or less at TWSC intersections. Same assumptions as “Delay & LOS.” During the a.m. and p.m. peak hours, the minor-street left-turn delay will be 22 seconds or less at TWSC intersections. Same assumptions as “Delay & LOS.” During the a.m. and p.m. peak hours, minor-street delay for any movement at any roundabout will be 10 seconds or less. Roundabouts have the lowest delay, followed by the couplet. Bicyclist comfort The road diet creates a bicycle lane in each direction on Ocean Drive. In some areas, bicyclists ride behind angle parking, which may reduce their visibility. Southbound bicyclists on Ocean Drive ride through the parking area and are separated from through auto traffic. Northbound bicyclists share a lane with autos on Palm Drive, as they do on Ocean Drive today. Between intersections, conditions are similar to Alternative 1 (including the potential for reducing visibility) but with lower auto speeds. Roundabouts may improve intersection comfort for side- street bicyclists at intersections that are currently TWSC. Each alternative improves comfort; the roundabouts may create lower vehicle speeds. Estimated construc- tion cost $3 million. $10 million. $6 million. Alternative 1 has the lowest cost, followed by Alternative 3. Exhibit 2-12: Alternatives Analysis Con’t

Evaluating the Performance of Corridors with Roundabouts Page A-64 Example Application #2 Perfor- mance Measure Alternative 1 – Road Diet with Signals and TWSC Alternative 2 – One-Way Couplet with Signals and TWSC Alternative 3 – Road Diet with Roundabouts Comments Anticipated impact on businesses Business owners generally believe this alternative would result in a modest increase in profits due to the increased parking and enhanced pedestrian environment. Business owners are concerned that removing northbound traffic from Ocean Drive would decrease the visibility of their businesses and thus their profits. A few business owners are supportive of this plan because it would create well- defined parking areas. Business owners generally believe this alternative would result in an increase in profits, and the increase would be greater than under Alternative 1 because of the greater investment in and appearance of the corridor. A few business owners are concerned that drivers and pedestrians will be uncomfortable with the roundabouts and avoid the area. Business owners are generally supportive of the road diet, with or without roundabouts. Walkability The road diet would improve walkability by reducing crossing length, providing ROW for sidewalk improvements, and introducing a facility for another active transportation mode (the bicycle lanes). However, crossing Ocean Drive might remain challenging at TWSC intersections. A one-way Ocean Drive would have fewer lanes and likely more gaps for pedestrian crossings. However, vehicle speeds are unlikely to be reduced and separation of parking from other roadway elements creates an environment that is generally more auto- centric and less walkable. The walkability of this alternative will be similar to Alternative 1, although vehicles will travel slower at roundabouts than at TWSC intersections. The road diet with or without roundabouts appears to improve walkability. Roundabouts may reduce speeds, making Ocean Drive crossings easier. Property value Most property owners believe this alternative will result in a modest increase in property value because of the increased parking supply and enhanced walkability. Some believe it will have no impact. Owners of property on Palm Drive are concerned that increased traffic will decrease their property value. Residential property owners on Ocean Drive do not anticipate significant impacts to property value. Commercial property owners on Ocean Drive are concerned that reduced traffic may decrease their property value. Most property owners believe this alternative will result in a modest increase in property value, similar to Alternative 1. A few are concerned that roundabouts will decrease property value. Property owners believe the road diet with or without roundabouts will increase property value and the couplet will decrease property value. Exhibit 2-12: Alternatives Analysis Con’t

Evaluating the Performance of Corridors with Roundabouts Example Application #2 Page A-65 Perfor- mance Measure Alternative 1 – Road Diet with Signals and TWSC Alternative 2 – One-Way Couplet with Signals and TWSC Alternative 3 – Road Diet with Roundabouts Comments Aesthetics By changing the cross-section of the roadway, this alternative creates the opportunity for aesthetic improvements such as landscaping and decorative pavement. This alternative creates the opportunity for aesthetic improvements on both Ocean Drive and Palm Drive. However, the dedicated parking areas on Ocean Drive may be visually unappealing. This alternative offers greater aesthetic potential than Alternative 1. The roundabouts may be landscaped, and they may also define the corridor and provide a sense of place. All alternatives create opportunity for aesthetic improve- ments. Com- munity accep- tance Community members generally feel this alternative improves the corridor but fails to address vehicular and pedestrian concerns at the TWSC intersections. The majority of the community is opposed to this alternative. Palm Drive residents are concerned about increased traffic and Ocean Drive business owners are concerned about decreased traffic. Reaction to the dedicated parking areas is mixed. Most community members prefer this alternative and feel it offers the greatest potential to improve the image and walkability of the corridor. It addresses their concerns about the TWSC intersections by removing them. A few community members have concerns about roundabouts and are strongly opposed to this alternative. The community generally prefers roundabouts and is opposed to the couplet. Public outreach and education may help address concerns about roundabouts. Parking supply This alternative adds 48 parking spaces, a 23% increase. This alternative adds 100 parking spaces, a 48% increase. This alternative adds 38 parking spaces, an 18% increase. The couplet adds the most parking, followed by Alternative 1. 2.3.1.1. Roundabout Influence Area Length Computation Example The roundabout influence area was calculated for one of the roundabouts on Ocean Drive to get a sense of the extent of areas in which speeds will be reduced due to the presence of roundabouts. Data used in these calculations are listed below: Upstream sub segment length = 350 feet; Downstream sub segment length = 420 feet; Central island diameter = 50 feet; Circulating speed = 20 mph; and The influence areas do not overlap (see Step B of the modeling framework in Chapter 3 of the main report). First, the free flow speed was determined using the upstream and downstream sub segment models: Exhibit 2-12: Alternatives Analysis Con’t

Evaluating the Performance of Corridors with Roundabouts Page A-66 Example Application #2 = 36.1 mph = 36.4 mph Using free flow speed values, the corresponding roundabout influence areas can be computed as follows: = 242 feet = 544 feet These values indicate that the influence areas do not overlap, so the assumption in Step B was correct. Intersections on Ocean Drive are spaced between 600 and 800 feet apart. Most of the corridor will lie within a roundabout influence area, meaning that the geometry of roundabouts will limit speeds along most of the corridor. 2.3.2. IDENTIFY PREFERRED ALTERNATIVE Alternative 2 (the one way couplet) was eliminated based upon negative feedback from the community. It was also the most expensive alternative. Many in the community supported Alternative 1 (road diet with existing traffic control). Most supported Alternative 3 as most desirable, as it would provide greater benefits in terms of traffic calming and the overall image of the corridor, even if it offered less additional parking than Alternative 1. Several roundabouts had been installed in other neighborhoods of the city, and both residents and city staff members were pleased with their performance, which made the city willing to install more. The city selected Alternative 3 based on strong support from the community. Residents and business owners advocated for Alternative 3 based on their belief it would improve the business environment on the corridor and improve aesthetics.

Evaluating the Performance of Corridors with Roundabouts Example Application #3 Page A-67 EXAMPLE APPLICATION 3. US 7 This fictional example application presents a context sensitive access management project on a rural corridor beginning to suburbanize. 3.1. PROJECT INITIATION Steps in the Project Initiation phase of the Project-Planning Process (refer to Corridor Comparison Document, Chapter 3) Cross-Section 2 lanes Travel Lanes 1 each direction Corridor Length 3.25 miles Forecast ADT 14,000 veh/day Forecast Peak-Hour Peak-Direction Flow 450 to 600 veh/h 85th Percentile Speed 46 mph Existing Control Signal at US 7/SR 272, TWSC elsewhere Peak-Hour Pedestrian Volume Along US 7 5 to 30 p/h Peak-Hour Pedestrian Volume Crossing US 7 10 to 25 p/h per intersection Sidewalks Varies Bicycle Lanes No Local Bus Service No Land Use Rural, changing to suburban Exhibit 3-1: Key Data

Evaluating the Performance of Corridors with Roundabouts Page A-68 Example Application #3 3.1.1. UNDERSTANDING OF CONTEXT Elk Grove is a historically rural town that experienced substantially increased population growth the past decade. A metropolitan area with three million people lies 75 miles to the south, and Elk Grove emerged as a popular location for second homes and retirement homes due to its natural beauty and rural character. US 7 is a two lane roadway through Elk Grove, and improvements to a 3.25 mile segment are under consideration. Due to increased growth in the area, the state DOT wants to address access management issues on US 7 in Elk Grove. US 7 is the primary link between Elk Grove and the metropolitan area to the south. It is a two lane, rural highway. Fifteen years ago, the state DOT improved a mountainous, four mile section of US 7 immediately south of Elk Grove and added truck climbing lanes. Within Elk Grove, there have been few improvements to the roadway in recent decades. Some businesses have parking lots without defined driveways directly fronting the roadway. Some houses lack driveways, and residents parallel park along the edge of the roadway. Two two way stop controlled intersections have left turn lanes on US 7. The only signal on US 7 in the area is at SR 272; the DOT signalized this intersection over 30 years ago. A half mile section of US 7 in Elk Grove has sidewalks that are in need of repair. There are no dedicated bicycle facilities on US 7. The town is interested in pedestrian and bicycle enhancements as part of the access management project. The project area is shown in Exhibit 3 2.

Evaluating the Performance of Corridors with Roundabouts Example Application #3 Page A-69 3.1.2. USERS AND TRAFFIC VOLUME US 7 serves a variety of users. The design year forecast ADT within Elk Grove is 14,000 veh/day, and forecast peak hour, peak direction flows range from 450 to 600 veh/h. Eighty fifth percentile speeds along US 7 are approximately 46 miles Exhibit 3-2: Existing Corridor

Evaluating the Performance of Corridors with Roundabouts Page A-70 Example Application #3 per hour. There is relatively lile east west traffic crossing the corridor, and only SR 272 has more than 150 side street vehicles in the peak hour. Crash rates on US 7 over the past five years are near the state average for similar facilities. Pedestrian volumes along US 7 range from 5 to 30 persons during the peak hour, and pedestrian volumes crossing US 7 at each intersection range from 10 to 25 persons during the peak hour. Pedestrian activity is highest in the southern portion of Elk Grove. No bicycle counts are available and there is no local bus service. For brevity, the fictional example applications only include volumes from one year. Generally, a planning study for a corridor would forecast future, design year volumes and practitioners would use these volumes for planning and analysis. 3.1.3. PROJECT CATALYST AND GOALS The DOT is concerned that ongoing growth in Elk Grove may lead to increased access onto US 7, potentially decreasing operational and safety performance. The town wishes to improve the aesthetics of US 7, which serves as their Main Street. Residents desire sidewalks and bicycle lanes and have identified and shared their difficulty crossing US 7 at TWSC intersections. The primary goals of the project are to: Improve access management, Improve the aesthetics, and Provide pedestrian and bicycle facilities. 3.1.4. SELECT AND PRIORITIZE PERFORMANCE MEASURES The sections below list the six groups of performance measures discussed in the CCD, and identify specific performance measures of importance on the US 7 corridor. The performance measures identified below are not necessarily all that could be considered for the US 7 project. There are many performance measures that could be used to evaluate a corridor. Some are of critical importance for nearly all corridors (Tier I), and others are only applicable to some corridors (Tiers II and III). For the purpose of illustrating the use of the CCD, this example presents performance measures of particular interest on the US 7 corridor and that help to distinguish the alternatives from one another. This includes Tier I measures like intersection level of service and cost, and Tier II and III measures like impacts to public facilities and livability. Performance measures of strong interest to the community are generally prioritized over those of lesser interest to the community. 3.1.4.1. Quality of Service Performance Measures Quality of service refers to auto traffic operations and the experience of other corridor users such as pedestrians, bicyclists, and transit riders. Auto traffic operations are generally quantified with the procedures of the Highway Capacity Manual. The quality of service for other users is generally assessed qualitatively or with the multimodal procedures of the Highway Capacity Manual.

Evaluating the Performance of Corridors with Roundabouts Example Application #3 Page A-71 The DOT has level of service and volume to capacity (v/c) ratio standards for new or reconstructed state highways, and DOT policy requires these standards to be assessed at the planning stage of the project. Currently, pedestrians have difficulty crossing US 7 due to the high vehicle speeds and few gaps in the traffic stream. Key Performance Measures: Intersection level of service, intersection capacity, arterial capacity, availability of gaps for pedestrian crossings. 3.1.4.2. Safety Performance Measures US 7 currently operates acceptably from a safety perspective. The state DOT wants to maintain this level of performance into the future, when volumes are forecast to increase. This desire may be partially addressed through access management improvements (see Section 3.1.4.6) that preserve available segment capacity and enhance traffic flow by reducing conflicts and friction at driveways. Reducing driveway conflicts on US 7 is beneficial for bicyclists and pedestrians traveling along US 7. Pedestrian and bicycle activity is expected to increase if improvements are made on the corridor. Treatments that promote pedestrian and cyclist safety could be integrated into potential project solutions. Key Performance Measures: Conflict points, auto/bicycle speed differential, pedestrian level of service, bicycle level of service. 3.1.4.3. Environmental Performance Measures Much of the land surrounding Elk Grove is publicly owned. Many residents and visitors take advantage of the close proximity of this land and the recreational opportunities it offers. The Red River is the largest river in this part of the state and is a valued recreational and natural resource. Key Performance Measure: Impacts to public facilities. 3.1.4.4. Cost Performance Measures Any build alternative will have capital construction costs, although they may vary greatly. Improvements expanding the footprint of the roadway or using a new alignment will require buying right of way. Key Performance Measures: Right of way acquisition cost, construction cost. 3.1.4.5. Community Value Performance Measures US 7 is the Main Street of Elk Grove and a key element of the town’s identity. Some residents and town officials are concerned the current roadway appearance negatively impacts people’s perceptions of the community. The poor condition of sidewalks, where they exist, discourages residents from walking. Curbs, pavement, and other elements of the roadway are in poor condition as well. These conditions detract from the Main Street image of US 7. Residents believe it is an opportune time to address aesthetics as part of the DOT’s access management efforts. Key Performance Measures: Livability, walkability, aesthetics, community acceptance.

Evaluating the Performance of Corridors with Roundabouts Page A-72 Example Application #3 3.1.4.6. Other Performance Measures The DOT initiated this project to beer manage access on US 7. The following access management issues are present: Side streets and driveways are full access (no left turn restrictions). Some parking lots continuously front the roadway, with no defined driveways. Driveways are generally unconsolidated, with each house and business having a dedicated access. Drivers park on the shoulders of the roadway and within DOT right of way off the shoulders. Key Performance Measure: Access management (such as driveway closures or consolidations and beer defining driveway accesses). 3.2. CONCEPT DEVELOPMENT Steps in the Concept Development phase of the Project-Planning Process (refer to Corridor Comparison Document, Chapter 3) 3.2.1. DEVELOP ALTERNATIVES AND PRELIMINARY OPERATIONS AND SAFETY ANALYSIS The DOT considered three alternatives for US 7: 1. Alternative #1 is a three lane roadway with a two way left turn lane (TWLTL) and bicycle lanes. Sidewalks are added. Three traffic signals are added at intersections where warrants are satisfied, and some driveways are consolidated to direct traffic to the signals. 2. Alternative #2 varies between a two lane roadway with a raised median and a three lane roadway with left turn lanes. Sidewalks and bicycle lanes are added. Five roundabouts are added, and some driveways are consolidated to direct traffic to the roundabouts. 3. Alternative #3 is a bypass from south of Elk Grove to SR 272 that reduces regional trips on existing US 7 in Elk Grove. Sidewalks and sharrows are added to existing US 7 in Elk Grove. The DOT used a software program implementing the HCM signalized intersection procedure to assess future lane needs for Alternative 1. DOT staff assumed a single lane approach on side streets and a two lane approach with a

Evaluating the Performance of Corridors with Roundabouts Example Application #3 Page A-73 through right lane and a left turn lane on US 7. The analysis determined this lane configuration is adequate to meet DOT performance criteria. The DOT used Exhibits 3 12 and 3 14 of NCHRP Report 672 to assess roundabout lane needs for Alternative 2 based upon ADT and peak hour volume. Use of Exhibit 3 12 was previously shown in Example Application 1 (Exhibit 1 3) and use of Exhibit 3 14 was previously shown in Example Application 2 (Exhibit 2 8). DOT staff determined single lane roundabouts will adequately serve forecast traffic on US 7. Under Alternative 3, traffic forecasts call for an ADT of 9,000 on the new bypass and 5,000 on existing US 7. The state’s transportation planning guidelines recommend that new rural roadways with an ADT of 15,000 or higher have four lanes. The forecast for the new bypass is below that threshold, and a two lane roadway will be sufficient. Some three lane sections with truck climbing lanes may be desirable on either side of the Red River crossing. 3.2.2. CONCEPTUAL LAYOUTS Following the initial operational checks, the DOT developed two conceptual layouts for each alternative. One layout is an overview of the entire corridor, and the other is a more detailed concept for a short segment of the corridor several blocks in length. The detailed concepts were used at a public meeting and provided a visualization of specific design elements of each alternative. Exhibits 3 3 through 3 7 depict the conceptual layouts of the three alternatives.

Evaluating the Performance of Corridors with Roundabouts Page A-74 Example Application #3 Exhibit 3-3: Alternative 1 Overview

Evaluating the Performance of Corridors with Roundabouts Example Application #3 Page A-75 Exhibit 3-4: Representative Segment of Alternative 1

Evaluating the Performance of Corridors with Roundabouts Page A-76 Example Application #3 Exhibit 3-5: Alternative 2 Overview

Evaluating the Performance of Corridors with Roundabouts Example Application #3 Page A-77 Exhibit 3-6: Representative Segment of Alternative 2

Evaluating the Performance of Corridors with Roundabouts Page A-78 Example Application #3 Exhibit 3-7: Alternative 3 Overview

Evaluating the Performance of Corridors with Roundabouts Example Application #3 Page A-79 3.3. ALTERNATIVES ANALYSIS Steps in the Alternatives Analysis phase of the Project-Planning Process (refer to Corridor Comparison Document, Chapter 3) 3.3.1. EVALUATE THE ALTERNATIVES Exhibit 3 8 summarizes an analysis of the three alternatives proposed for US 7 using the key performance measures identified in Section 3.1.4.

Evaluating the Performance of Corridors with Roundabouts Page A-80 Example Application #3 Perfor- mance Measure Alternative 1 – Signals and TWLTL Alternative 2 – Roundabouts and Median Alternative 3 – Two-Lane Bypass Comments LOS During the a.m. and p.m. peak hours, the three new signalized intersections will operate at LOS A or B. During the a.m. and p.m. peak hours, the five roundabouts will operate at LOS A or B. During the a.m. and p.m. peak hours, the signals or roundabouts at the endpoints of the bypass will operate at LOS B or C. Intersections on existing US 7 will remain TWSC and operate acceptably. For each alternative, intersection operations are similar and meet the DOT’s standard of LOS D or better. Intersec- tion capacity During the a.m. and p.m. peak hours, the three new signalized intersections will operate at a v/c of 0.59 or better. During the a.m. and p.m. peak hours, the five roundabouts will operate at a v/c of 0.71 or better. During the a.m. and p.m. peak hours, signals at the end of the bypass would operate at a v/c of 0.67 or better. Roundabouts would operate at 0.80 or better. For each alternative, intersections meet the DOT’s standard of 0.95 or lower for signals and 0.85 or lower for roundabouts. Arterial capacity The state DOT requires new highways be 4-lane if the ADT is 15,000 or greater. The forecast ADT of US 7 is 14,000 and a TWLTL will be added. The roadway links will be below capacity. Intersections will operate below capacity (see above) and not constrain the roadway. According to Exhibit 3- 12 of NCHRP Report 672, single-lane roundabouts are likely to operate acceptably with an ADT under 15,000. During a.m. and p.m. peak hours, the v/c of the bypass (per the HCM two- lane highway procedure) will be 0.41 or better. All alternatives provide adequate roadway capacity. Availability of gaps for pedestrian crossings Signals create additional mid-block gaps on US 7 by stopping major street traffic at nearby intersections and forming platoons of vehicles. Alternative 1 also includes several pedestrian refuge islands that create opportunities for two- stage crossings. Three signalized crossings are provided. Fewer platoons are likely to form with roundabouts than with signals. Five roundabouts with two- stage crossings are provided. The reduced traffic volume on US 7 creates additional gaps. No signals or roundabouts are available to assist pedestrians with a crossing. The differences between the alternatives are unclear. This performance measure does little to inform the selection of corridor alternatives. Exhibit 3-8: Alternatives Analysis

Evaluating the Performance of Corridors with Roundabouts Example Application #3 Page A-81 Perfor- mance Measure Alternative 1 – Signals and TWLTL Alternative 2 – Roundabouts and Median Alternative 3 – Two-Lane Bypass Comments Conflict points The number of intersection conflict points remains approximately the same. A four-leg intersection with single-lane approaches has 32 auto-auto conflict points and 24 auto- pedestrian conflict points. Some mid-block conflict points are eliminated by driveway closures or consolidations. The number of intersection conflict points is reduced. A four-leg, single-lane roundabout has 8 auto-auto conflict points and 8 auto- pedestrian conflict points. The median reduces mid-block conflict points to a greater degree than Alternative 1. Conflict points on existing US 7 will remain, although traffic volume will be reduced by more than half. The new roadway will have three to five driveways, plus the intersections at the endpoints. Alternative 2 eliminates the most intersection and mid- block conflict points. Auto/Bicycle speed differential (see Section 3.3.1.1) Based on a study of a similar roadway, the DOT estimates bicyclists on US 7 currently travel 12 – 14 mph. The 85th percentile auto speed is currently 46 mph. Signals will slow some proportion of auto and bicycle traffic because they will sometimes be red. The effect of the TWLTL on auto speed is unclear. Vehicles will slow to 25 miles per hour or less when passing through a roundabout. Compared to existing conditions, the auto/bicycle speed differential will be reduced within the roundabout influence area, which will extend 300-400 feet upstream and 800- 900 feet downstream of each roundabout (see calculations in Section 3.3.1.1). Roundabouts are located substantially further apart than this, so most of the corridor will not have a reduced auto/bicycle speed differential. Bicyclists will be encouraged to use existing US 7 rather than the bypass. With few physical changes to the roadway, auto speeds and the auto/bicycle speed differential can be expected to remain similar. Alternative 2 reduces the auto/bicycle speed differential on some portions of the corridor compared to other alternatives. Pedestrian level of service (see Section 3.3.1.1) Pedestrian LOS improves by adding a sidewalk, signals, and a buffer (bike lane) between autos and pedestrians. Pedestrian LOS improves by adding a sidewalk and a buffer (bike lane) between autos and pedestrians, reduced auto speeds, and decreased intersection width. Pedestrian LOS improves due to the addition of a sidewalk and reduction in auto volume. Alternatives 1 and 2 improve pedestrian LOS to a greater degree than Alternative 3. Bicycle level of service Bicycle LOS improves by adding a bike lane and reduction in the number of access points. Bicycle LOS improves by adding a bike lane, reduction in the number of access points, and reduced auto speeds. Bicycle LOS improves due to reduced auto volumes. Alternatives 1 and 2 improve bicycle LOS to a greater degree than Alternative 3. Exhibit 3-8: Alternatives Analysis Con’t

Evaluating the Performance of Corridors with Roundabouts Page A-82 Example Application #3 Perfor- mance Measure Alternative 1 – Signals and TWLTL Alternative 2 – Roundabouts and Median Alternative 3 – Two-Lane Bypass Comments Impacts to public facilities The DOT will purchase a 7-foot- wide strip of land from a local school to accommodate a widened US 7. This is currently part of a lawn and impacts are considered minimal. The DOT will purchase a 7-foot-wide strip and a triangular piece of land from a local school to accommodate a widened US 7 and a roundabout. This is currently part of a lawn, and impacts are considered minimal. The new roadway will primarily be located on public land. Several hiking trails will need to be relocated, and there will be a decrease in the overall amount of recreational land. Alternative 3 has the greatest impacts to public facilities. Estimated right-of- way cost $400,000. $500,000. $1.8 million. Alternative 3 is more than three times the cost of the others. Alternatives 1 and 2 are of similar magnitude. Estimated construc- tion cost $2.2 million. $3.1 million. $16 million. Alternative 3 is more than five times the cost of the others. Alternative 1 is the lowest. Livability Alternative 1 improves the roadway with curbs, sidewalks, new pavement, and other enhancements. However, the TWLTL may create a suburban feel for the roadway and surrounding area. Alternative 2 also improves the roadway with curbs, sidewalks, and new pavement. Additionally, the landscaping in the median and roundabout central islands complements the rural and natural character. Roundabouts slow vehicles, and create a gateway into Elk Grove. Alternative 3 has the fewest improvements within Elk Grove. The traffic volume on existing US 7 is reduced, but the context of the new roadway may be inconsistent with the surrounding area. Alternatives 1 and 2 improve existing US 7 and enhance livability to a greater degree than Alternative 3. Alternatives 1 and 3 create facilities that may be inconsistent with the character of Elk Grove. Walkability Adding sidewalks and creating defined driveways improves walkability and bicycling conditions. The widening of the road from two lanes to three may have a negative impact on walkability. Like Alternative 1, adding sidewalks and creating defined driveways improves walkability and bicycling conditions. A median allows for two- stage crossings and the roadway remains two lanes. Vehicle speeds are reduced in the vicinity of the roundabouts. Adding sidewalks and reducing traffic volume improve walkability and bicycling conditions. Alternatives 1 and 2 feature more physical improvements than Alternative 3. Alternative 2 has one less lane on the roadway than Alternative 1, and changes control at five intersections (roundabouts) versus three intersections (signals). Exhibit 3-8: Alternatives Analysis Con’t

Evaluating the Performance of Corridors with Roundabouts Example Application #3 Page A-83 Perfor- mance Measure Alternative 1 – Signals and TWLTL Alternative 2 – Roundabouts and Median Alternative 3 – Two-Lane Bypass Comments Aesthetics Streetscape improvements such as new sidewalks and curbs will improve the appearance of the corridor. Alternative 2 includes many of the same streetscape improvements as Alternative 1. Plus, the median and the roundabout central islands create opportunities for enhancing landscaping and the rural and natural context of the corridor. Alternative 3 has fewer aesthetic improvements to existing US 7 than other alternatives. The new roadway may detract from the vistas of the Red River canyon outside of Elk Grove. Alternative 2 offers the greatest potential for aesthetic improvements. Communi- ty acceptance Community members generally agree Alternative 1 improves the corridor to a marginal degree. Many in the community support the context-sensitive nature of Alternative 2. The potential for landscaping and concept of roundabouts as gateways are supported by citizens and officials in Elk Grove. However, there is some concern roundabouts will be confusing to drivers and increase crashes. There is little support for Alternative 3 within Elk Grove. It has the fewest improvements to the existing roadway and impacts undeveloped land outside of the town. Businesses in Elk Grove that serve through travelers are concerned about diverting traffic onto the new roadway. Alternative 3 is supported by the owners of several industrial businesses along SR 272 for mobility reasons. The community is most supportive of Alternative 2 and least supportive of Alternative 3. Access manage- ment Alternative 1 eliminates parking lot access that continuously fronts the roadway and replaces it with defined and consolidated driveways. Some existing driveways near new signalized intersections are closed, such as those serving properties with other access points. Alternative 2 eliminates more driveways than Alternative 1, and the median restricts many driveways with right-in right-out access. Roundabouts enable U-turns and indirect left turns. Like Alternative 1, Alternative 2 eliminates parking lot access that continuously fronts the roadway. Alternative 3 does not change access points on existing US 7. Alternative 2 offers the greatest access- management benefit. Exhibit 3-8 Alternatives Analysis Con’t

Evaluating the Performance of Corridors with Roundabouts Page A-84 Example Application #3 3.3.1.1. Roundabout Influence Area Length Computation Example Roundabout influence area was calculated for one of the roundabouts on US 7 to get a sense of the extent of areas in which speeds will be reduced due to the presence of roundabouts. Data used in these calculations are listed below: Upstream sub segment length = 2,145 feet; Downstream sub segment length = 2,215 feet; Central island diameter = 50 feet; Circulating speed = 20 mph; and The influence areas do not overlap (see Step B of the modeling framework in Chapter 3 of the main report). First, the free flow speed was determined using the upstream and downstream sub segment models: = 44.9 mph = 45.8 mph Using these values, the corresponding roundabout influence areas can be computed as follows: = 363 feet = 838 feet These values indicate the influence areas do not overlap, so the assumption they do not was correct. Intersections on US 7 are spaced at a distance much greater than 840 feet. Most of the corridor will not lie within a roundabout influence area, meaning roundabouts will not reduce speeds at most locations along the corridor. 3.3.2. IDENTIFY PREFERRED ALTERNATIVE Alternative 3 was eliminated based upon the high construction cost, impact to public land, and negative feedback from the community. The town of Elk Grove advocated for Alternative 2 because it was favored by a…endees of public meetings, and offered place making and aesthetic improvement opportunities in context with the surrounding land. The town believes Alternative 2 will preserve the integrity of US 7 serving as the Main Street of their community, rather than just a through highway. The town was encouraged by national data showing roundabouts reduce the number and severity of crashes compared to conventional intersection forms. The town offered to maintain roundabout and median landscaping. The town and the DOT executed a memorandum of understanding solidifying the agency partnership.

Evaluating the Performance of Corridors with Roundabouts Example Application #3 Page A-85 Maintenance of these elements was a concern of the DOT. The DOT selected Alternative 2 based on access management benefits and support from the community.

Evaluating the Performance of Corridors with Roundabouts Example Application #4 Page A-87 EXAMPLE APPLICATION 4. STEVENS STREET This fictional example application presents a suburban corridor being rebuilt for maintenance reasons. The project presents an opportunity to remake the image of the corridor and implement safety improvements. 4.1. PROJECT INITIATION Steps in the Project Initiation phase of the Project-Planning Process (refer to Corridor Comparison Document, Chapter 3) Cross-Section 6 lanes with raised median Travel Lanes 3 each direction Forecast ADT 30,000 veh/day Peak-Hour Pedestrian Volume Crossing Corridor 0 to 20 p/h per intersection Peak-Hour Pedestrian Volume Along Corridor 0 to 10 p/h Sidewalks Varies by segment, existing sidewalks generally in poor condition Local Bus Service 60 minute headways Land Use Suburban 4.1.1. UNDERSTANDING OF CONTEXT Fifteen years ago, the Falls to Fort Expressway opened. This facility improved mobility between Francis Falls and Fort Nestor and reduced traffic volume on Exhibit 4-1: Key Data

Evaluating the Performance of Corridors with Roundabouts Page A-88 Example Application #4 Stevens Street, which previously served as the primary route between the two cities. The segment of Stevens Street between the Falls to Fort Expressway and SR 71 is nearly five miles long and has 15 signalized intersections. It was originally a two lane roadway, widened to four lanes with a median in the 1960s. It was widened to six lanes in the 1980s. The posted speed limit is 40 miles per hour, and 85th percentile speeds range from 45 to 50 mph along the corridor. The Fort Nestor/Francis Falls area, including Stevens Street, is shown in Exhibit 4 2. A representative intersection on Stevens Street is shown in Exhibit 4 3 in the Concept Development section of this example application. 4.1.2. USERS AND TRAFFIC VOLUME The design year forecast ADT on Stevens Street is 30,000. This represents an increase from the current ADT of 26,000, and remains below the ADT of 44,000 recorded the year before the Falls to Fort Expressway opened. Stevens Street is an auto focused facility. Sidewalks are present along the corridor, but they have been poorly maintained and most blocks have 10 or fewer pedestrians walking along the corridor during the peak hour. Peak hour pedestrian crossing volumes at signalized intersections range from 0 to 20. There is less bicycle activity than pedestrian activity. Most of the roadway has no shoulder due, in part, to the widening in the 1980s. A bus route with 60 minute headways operates on the corridor. For brevity, the fictional example applications only include volumes from one year. Generally, a planning study for a corridor would forecast future, design year volumes and practitioners would use these volumes for planning and analysis. Exhibit 4-2: Proposed Corridor Alignment

Evaluating the Performance of Corridors with Roundabouts Example Application #4 Page A-89 4.1.3. PROJECT CATALYST AND GOALS Stevens Street is in need of maintenance. Most of the roadway has been resurfaced several times and Fort Nestor wants to remove all layers of pavement and rebuild the roadway from the subgrade up to minimize future pavement maintenance needs. The city and community groups are interested in reviving the retail market along Stevens Street. Most of the commercial buildings along the corridor were constructed prior to 1985 and some major retailers have moved to newer properties along Whitefish Drive or SR 71. Commercial properties on Stevens Street have a vacancy rate above the city average. This project presents the city with an opportunity to remake the image and design of Stevens Street. 4.1.4. SELECT AND PRIORITIZE PERFORMANCE MEASURES The sections below list the six groups of performance measures discussed in the Corridor Comparison Document (CCD) and identify specific performance measures of importance on the Stevens Street corridor. The performance measures identified below are not necessarily all that could be considered for the Stevens Street project. Many performance measures could be used to evaluate a corridor. Some are of critical importance for nearly all corridors (Tier I), and others are only applicable to some corridors (Tiers II and III). For the purpose of illustrating the use of the CCD, this example presents performance measures of particular interest on the Stevens Street corridor that help to distinguish the alternatives from one another. This includes Tier I measures like intersection level of service and cost, and Tier II and III measures like economic development. Performance measures of strong interest to the community are generally prioritized over those of lesser interest to the community. 4.1.4.1. Quality of Service Performance Measures Stevens Street may be capable of meeting operating standards with a reduced number of lanes. Changes to lane configurations, intersections, or other roadway elements also have the potential to positively change pedestrian quality of service. Key Performance Measures: Peak hour intersection level of service, intersection capacity, Urban Street LOS for pedestrians. 4.1.4.2. Safety Performance Measures Rear end crashes are the most frequently occurring crash type at signalized intersections on Stevens Street. City engineers a‰ribute some of these crashes to high speeds on Stevens Street, and believe reducing speeds will improve intersection safety. Corridor residents also expressed interest in speed reduction. The city will explore using the HSM to quantitatively assess how potential geometric changes in various alternatives may change safety performance. Key Performance Measure: Predicted changes in crash frequency at intersections. 4.1.4.3. Environmental Performance Measures This project will modify an existing roadway in a developed suburban area. Li‰le or no undeveloped land will be disturbed. There are several parks and

Evaluating the Performance of Corridors with Roundabouts Page A-90 Example Application #4 schools in the project area away from Stevens Street. It is unlikely these facilities will be impacted. Key Performance Measures: None. 4.1.4.4. Cost Performance Measures Rebuilding Stevens Street will be the largest project undertaken by the city of Fort Nestor in recent years. Some funds are programmed, but they may not be sufficient for all alternatives. Due to the condition of the pavement on Stevens Street, the city does not intend to delay the project. Alternatives costing more than programmed funding are likely infeasible. Key Performance Measures: Pre construction costs such as planning, preliminary engineering, and final design; right of way acquisition cost; capital construction cost. 4.1.4.5. Community Value Performance Measures Stevens Street is the main arterial link between Fort Nestor and Francis Falls. Stakeholders want to improve the image of the corridor and transform it into a signature roadway that defines the community. This could also establish a sense of place and appeal to businesses and consumers. Key Performance Measures: Aesthetics, place making, overall public opinion. 4.1.4.6. Other Performance Measures The city hopes this project revitalizes the Stevens Street corridor. Some larger, regional drawing stores moved to Whitefish Drive or SR 71 in recent years. Changes to Stevens Street may make it a more viable location for smaller, neighborhood serving businesses and reduce the commercial property vacancy rate. Key Performance Measures: Land use considerations, economic development/tax base considerations. 4.2. CONCEPT DEVELOPMENT Steps in the Concept Development phase of the Project-Planning Process (refer to CCD, Chapter 3) 4.2.1. DEVELOP ALTERNATIVES AND PRELIMINARY OPERATIONS AND SAFETY ANALYSIS With a forecast ADT of 32,000, two lanes in each direction should be sufficient for segment capacity needs. This creates an opportunity to reduce the number of travel lanes on Stevens Street.

Evaluating the Performance of Corridors with Roundabouts Example Application #4 Page A-91 Fort Nestor considered three alternatives for Stevens Street: 1. Alternative #1 rebuilds the pavement of the existing six lane roadway and replaces some signal equipment at the end of its life cycle. This is effectively a no build alternative. 2. Alternative #2 reduces the roadway to four lanes. The existing outside lanes are replaced with a bicycle lane, curb and gutter, and a widened sidewalk. Intersections remain signalized. 3. Alternative #3 reduces the roadway to four lanes and replaces signals with two lane roundabouts. The existing outside lanes are replaced with a bicycle lane, curb and gutter, and a widened sidewalk. Based on guidance in NCHRP Report 672 and the city’s experiences with roundabouts to date, Alternative 3 uses two lane roundabouts with inscribed circle diameters (ICDs) in the range of 180 to 200 feet. This will require right of way acquisition at most intersections, including acquiring and demolishing some structures. Exhibit 4 3 shows an intersection where existing right of way does not accommodate a roundabout. 4.2.2. CONCEPTUAL LAYOUTS Fort Nestor city staff developed typical sections of each alternative to present to the public and to decision makers. These typical sections are shown in Exhibits 4 4 and 4 5. The typical sections illustrate mid block (not intersection) conditions, so Alternatives 2 and 3 are depicted to be the same. Exhibit 4-3: Approximate Footprint of Roundabout at Existing Intersection

Evaluating the Performance of Corridors with Roundabouts Page A-92 Example Application #4 The city also developed plan view layouts of the alternatives to assess right of way needs and perform initial cost estimates. These layouts are omitted from the example application for brevity. 4.3. ALTERNATIVES ANALYSIS Steps in the Alternatives Analysis phase of the Project-Planning Process (refer to CCD, Chapter 3) 4.3.1. EVALUATE THE ALTERNATIVES Exhibit 4 6 summarizes an analysis of the three alternatives proposed for Stevens Street using the key performance measures identified in Section 4.1.4. Perfor- mance Measure Alternative 1 – Rebuild 6-Lane Existing Alternative 2 – 4-Lane with Signals Alternative 3 – 4-Lane with Roundabouts Comments Peak-hour intersec- tion LOS All signalized intersections operate at LOS C or better. Most operate at LOS B. All signalized intersections operate at LOS D or better. Most operate at LOS C or better. The critical movement at all roundabouts is LOS C or better. Intersections operate at LOS D or better under all alternatives. Exhibit 4-4: Alternative 1 Typical Section Exhibit 4-5: Alternatives 2 and 3 Typical Section Exhibit 4-6: Alternatives Analysis

Evaluating the Performance of Corridors with Roundabouts Example Application #4 Page A-93 Perfor- mance Measure Alternative 1 – Rebuild 6-Lane Existing Alternative 2 – 4-Lane with Signals Alternative 3 – 4-Lane with Roundabouts Comments Intersec- tion capacity All signalized intersections have a v/c of 0.73 or less. All signalized intersections have a v/c of 0.86 or less. All roundabouts have a critical- movement v/c of 0.82 or less. All intersections operate at acceptable levels. Urban Street LOS for pedestri- ans Many segments are LOS F because there is no sidewalk. Other segments vary from LOS C to E. All segments are LOS E or better. Most are LOS C or D. Results are similar to Alternative 2. The Pedestrian Urban Street LOS procedure in the HCM 2010 does not directly accommodate segments with roundabouts. Alternatives 2 and 3 provide a higher pedestrian LOS than Alternative 1. Predicted changes in crash frequency at intersec- tions (See Section 4.3.1.1) Few changes in crash frequency or severity are expected. Safety changes are unclear; see Section 4.3.1.1 for more detail. Per Exhibit 14-3 of the HSM, the CMF for replacing a suburban signalized intersection with a two-lane roundabout is 0.33 with a standard error of 0.05. Therefore, 0.23 to 0.43 times as many intersection crashes are expected with this alternative compared to existing conditions. Roundabouts also reduce the severity of crashes by reducing vehicle speeds and angle conflict points. A CMF for injury crashes in this situation (suburban signalized intersection replaced with two-lane roundabout) is not provided in the HSM. Alternative 3 is expected to reduce the frequency and severity of intersection crashes. Estimated pre- construc- tion cost $400,000. $1.1 million. $ 3.9 million. Alternative 3 is the most expensive, followed by Alternative 2. Estimated right-of- way acquisition cost $0. $400,000. For sidewalks in areas where current ROW is insufficient. $15 million. ROW is purchased at most intersections and several structures will be acquired. Alternative 3 is more than 30 times the cost of Alternative 2. Alternative 1 has no cost. Exhibit 4-6: Alternatives Analysis Con’t

Evaluating the Performance of Corridors with Roundabouts Page A-94 Example Application #4 Perfor- mance Measure Alternative 1 – Rebuild 6-Lane Existing Alternative 2 – 4-Lane with Signals Alternative 3 – 4-Lane with Roundabouts Comments Estimated capital construc- tion cost $5 million. $19 million. $29 million. Alternative 3 is $10 million more than Alternative 2. Alternative 2 is nearly triple the cost of Alternative 1. Intersec- tion operations and mainten- ance costs $120,000 annually, including signal maintenance, signal power supply, and signal retiming every several years. Similar to Alternative 1. $30,000 annually, primarily landscaping. Alternative 3 has the lowest costs. Aesthetics The corridor will look the same as today, but with new pavement. Addition of curb and gutter, sidewalks, and bicycle lanes creates a more urban appearance and shows the city’s investment in the corridor. In addition to improvements noted under Alternative 2, roundabouts make intersections more visually appealing and provide opportunities for landscaping, public art, and other decorative treatments. Alternatives 2 and 3 improve the aesthetics of the corridor. Alternative 3 creates more opportunities than Alternative 2. Place- making The corridor will essentially be the same place it is today. The corridor will look newer than other streets in this part of the city and have amenities such as sidewalks and bicycle lanes that are uncommon on Fort Nestor’s arterials. The corridor will be a unique and recognizable element of the city’s transportation network. Roundabouts serve as gateways and can help to brand the corridor. Place- making benefits noted under Alternative 2 exist as well. Alternative 3 creates the greatest sense of place, followed by Alternative 2. Land-use considera- tions Land use will likely remain similar to current conditions. The changes in the corridor may make it a more viable location for neighborhood- oriented businesses that would benefit from improved multi- modal conditions. The roadway will still have sufficient capacity for autos and remain a viable location for auto-oriented land uses. The uniqueness of the corridor may attract upscale and specialty businesses. Benefits noted under Alternative 2 exist as well. Alternatives 2 and 3 have the greatest potential to change land use in the corridor. Exhibit 4-6: Alternatives Analysis Con’t

Evaluating the Performance of Corridors with Roundabouts Example Application #4 Page A-95 Perfor- mance Measure Alternative 1 – Rebuild 6-Lane Existing Alternative 2 – 4-Lane with Signals Alternative 3 – 4-Lane with Roundabouts Comments Overall public opinion There is little support for this alternative. Approximately half of attendees to public meetings favor this alternative. Approximately half of attendees to public meetings favor this alternative. Some residents are concerned that driving the corridor will be slow and challenging due to the numerous roundabouts. Public opinion is generally divided between Alternatives 2 and 3. Economic develop- ment/tax- base considera- tions This alternative does not create an impetus for investment in the corridor. The visible signs of investment by the city and increased potential for neighborhood- oriented businesses may reduce the vacancy rate and encourage new construction. The potential for economic development is similar to Alternative 2. Some properties will be reduced in size and value due to the acquisition of land for the roundabouts. The greater magnitude of changes in the corridor compared to Alternative 2 could spur additional investment. Alternatives 2 and 3 may encourage economic development and improve the corridor. 4.3.1.1. Alternative 2 Predicted Change in Crash Frequency and Severity Part C of the HSM contains a predictive method for four lane divided arterials in Chapter 12 – Predictive Method for Urban and Suburban Arterials. However, there is no predictive method for six lane divided arterials in the HSM, and no calibration factors have been developed for the Fort Nestor/Francis Falls area. Comparing observed crash history of the existing roadway to an uncalibrated predictive model may not present a representative comparison. Also, Part D of the HSM does not have a crash modification factor for converting a six lane arterial to a four lane arterial. The HSM does not provide a means of comparing the safety performance of Alternative 2 to existing conditions. The decrease in speed discussed in the previous section may reduce the frequency and/or the severity of crashes. 4.3.2. IDENTIFY PREFERRED ALTERNATIVE Alternative 3 had the greatest potential to change the image and land use of the corridor. It would have created a unique corridor unlike any other in the city. However, public opinion was divided. Some residents favored roundabouts for the place making and traffic calming reasons, and others were concerned about repeatedly slowing when driving the corridor and felt a coordinated signal system would be operationally superior. City staff generally favored Alternative 3 for place making and economic development reasons as well as safety benefits. Exhibit 4-6: Alternatives Analysis Con’t

Evaluating the Performance of Corridors with Roundabouts Page A-96 Example Application #4 Unfortunately, Fort Nestor had only $25 million available for the Stevens Street project. This was enough to fund Alternative 2, but less than half of the estimated total cost (ROW, pre construction, construction) of Alternative 3. Sufficient funds for Alternative 3 would not have been available for at least five years. 4.3.3. ITERATION Alternative 3 was not financially feasible. However, city staff remained interested in constructing a roundabout at one intersection on the corridor: Stevens Street/Robinson Street. This is the fourth intersection northeast of SR 71 in Exhibit 4 2, where Stevens Street curves. The skew of this intersection has long created safety issues, and Alternatives 1 and 2 will not fundamentally change this. Residents and business owners on Stevens Street immediately east of this intersection expressed a strong desire for speed control, particularly to slow drivers leaving the mall area between Robinson Street and SR 71. 4.3.4. IDENTIFY MODIFIED PREFERRED ALTERNATIVE Fort Nestor selected a modified version of Alternative 2, with a roundabout at Stevens Street/Robinson Street and signals at other existing signalized intersections.

Abbreviations and acronyms used without definitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012) NASA National Aeronautics and Space Administration NASAO National Association of State Aviation Officials NCFRP National Cooperative Freight Research Program NCHRP National Cooperative Highway Research Program NHTSA National Highway Traffic Safety Administration NTSB National Transportation Safety Board PHMSA Pipeline and Hazardous Materials Safety Administration RITA Research and Innovative Technology Administration SAE Society of Automotive Engineers SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) TCRP Transit Cooperative Research Program TEA-21 Transportation Equity Act for the 21st Century (1998) TRB Transportation Research Board TSA Transportation Security Administration U.S.DOT United States Department of Transportation

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 772: Evaluating the Performance of Corridors with Roundabouts provides measurement and evaluation methods for comparing the performance of a corridor with a functionally interdependent series of roundabouts to a corridor with signalized intersections in order to arrive at a design solution.

For the purposes of this research, a “series of roundabouts” is defined as at least three roundabouts that function interdependently on an arterial.

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