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Performance-Based Analysis of Geometric Design of Highways and Streets (2014)

Chapter: Chapter 5 - Process Framework

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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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Suggested Citation:"Chapter 5 - Process Framework." National Academies of Sciences, Engineering, and Medicine. 2014. Performance-Based Analysis of Geometric Design of Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/22285.
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44 C H A P T E R 5 5.1 Introduction This chapter presents the performance-based analysis application framework. This chapter describes how performance-based analysis can be used to inform geometric design decisions within multiple phases of the project development process and within or outside of an envi- ronmental review process. The chapter provides a framework for applying the information in Chapter 4. Specifically, Section 4.4 highlights the relationships between different performance measures and geometric elements. Chapter 6 presents project examples illustrating how to apply the framework described below. Exhibit 5-1 illustrates the basic framework for integrating performance-based analysis into geometric design. This framework is applicable across the different stages of the project development process and within or outside of an environmental review process. The stages of the project development process were presented in Section 2.3. The specific considerations within the framework vary depending on where a project is within its development. As noted previously, as a project pro- gresses further toward final design, there are increasingly limited opportunities to significantly change its form, function, or performance. The application framework is organized into three broad phases: 1. Project initiation 2. Concept development 3. Evaluation and selection These three broad phases generally represent the activities leading up to the final project activities of developing project plans, specifications, and estimates. During project final plan preparation, new project developments can arise that might require “initiating” an evalua- tion of a design element or configuration and “developing concepts” that might appropriately address the needs of the new situation. Ultimately, the project designers will evaluate and select a solution for that geometric element or configuration. The ultimate decision, even for a rela- tively discrete component, may include estimating performance and financial feasibility of the design choices. Each of these phases contains steps or activities to meet the needs of each phase and build incrementally through the activities needed to initiate a project, develop concepts, evaluate options, and ultimately select or advance a project or design recommendations. The steps within each phase are presented in Sections 5.2 through 5.4. The information presented within those sections is applicable across the project development process. Considerations specific to envi- ronmental review are presented in Section 5.5, Environmental Review Process. Process Framework

Process Framework 45 5.2 Project Initiation The project initiation phase sets a foundation for understanding the project context and overarching intended outcomes. There are a variety of names for these activities depending on the transportation agency involved. And while the names may vary between agencies, the general intent of an activity initiating a project is consistent. Section 3.2 noted some of the examples of project catalysts generating a project. Regardless of the reason for a proj- ect’s inception, all projects have a unique context requiring customized solutions to meet project and geometric design outcomes. The project context often includes considerations about the following: • The existing site constraints • Current performance related to operations, safety, access, reliability, and quality of service • Surrounding land uses • Planned improvements for the future • Existing and future anticipated form and function of the facility • Other similar considerations Identifying and succinctly articulating the intended project outcomes include understanding the catalyst and motivations for the project, the target audience to be served by the project, the critical desired performance characteristics, and ultimately the performance measures that will be used to inform design decisions and solution development. These performance measures may stem from project-specific design controls, tailored to the unique project needs, helping to define the design criteria and dimensional design values targeted to achieve desired performance. The outcomes of the project initiation phase are as follows: 1. Clarity of the characteristics defining the current and desired future of the site 2. A clear and concise understanding of the primary project purpose 3. A set of performance measures to be used to evaluate a design’s impact on the desired project purpose Exhibit 5-1. Performance-based analysis application framework.

46 Performance-Based Analysis of Geometric Design of Highways and Streets The following subsections highlight activities and considerations for the two steps within the project initiation phase: 1. Project context 2. Intended outcomes 5.2.1 Project Context Understanding a project’s context helps (1) define the boundaries that improvements or project considerations should fall within and (2) identify critical surrounding characteris- tics potentially dictating the type, form, or function of a site-specific improvement or design decision. This step within the project initiation phase helps identify the facility users or spe- cial needs influencing geometric design decisions. This could include design controls such as vehicle type or target speeds of a facility in total, or for specific elements such as an interchange ramp. Understanding the user types and modal considerations helps establish target perfor- mance parameters. For example, if an intersection improvement project is identified for an intersection adjacent to an elementary school, the improvements should consider school bus circulation, crossing needs of school-age children on foot and on bicycles, parent drop-off and pick-up activi- ties, broader transit needs for school employees (e.g., teachers), and parking needs for school employees and visitors. Even if the overarching focus of the intersection project is not directly related to the elementary school, the design solutions should take into consideration the school and the associated road users who will use the intersection to access the school. If, in this example, one of the intersecting roadways served as a designated freight route, the design controls and associated performance measurement would balance the needs of vulner- able user crossing needs with dimensional values for design elements (i.e., lane width or turning radii) appropriate for the freight user needs. Similar considerations should be made for design solutions in agricultural areas, industrial areas, large employment centers, central business dis- tricts, and other locations where the surrounding land uses and destinations generate a wide range of road users and a wide range of needs. The following questions outline some considerations useful in helping to define the project context. As the needs of a given project can vary by element or combinations of conditions, each professional may use his or her own judgment to consider and customize the following questions to fit project-specific needs: • Where in the project development process is the project? • Is it a rural, suburban, or urban setting? • Who has jurisdiction of the roadways influenced by the project? • Are there pre-existing constraints? – Design concepts already identified? – Right-of-way constraints or limitations? – Community objectives or interests? – Funding limitations? – Environmental concerns or constraints? – Constructability challenges? – Project schedule challenges or critical milestones? • What is the highway’s or street’s role in the overall network? What is its functional classifica- tion? How does the facility need to adapt to various context zones along its route while meeting its intended purpose?

Process Framework 47 • What are the current defining geometric characteristics? – Segment considerations ▪ Cross section (e.g., number of through lanes, turn lanes, medians, on-street parking, bicycle lanes, sidewalks, landscaping) ▪ Horizontal alignment (e.g., curve radii, curve length, superelevation) ▪ Vertical alignment ▪ Target speed ▪ Posted speed ▪ Design speed ▪ Locations and treatments of mid-block crossings – Intersections ▪ Traffic control ▪ Target, posted, and design speed on approaches ▪ Signal phasing and timing ▪ Lane configurations ▪ Pedestrian treatments present ▪ Bicycle treatments present ▪ Design vehicle or special vehicle needs • What are the current performance characteristics of the highway or street? – Quality of service for road users (e.g., presence and condition of bicycle facilities or ability to serve design vehicles)? – Safety performance for road users (e.g., crash frequency and severity)? – Access available relative to street functional classification and role in the network? – Operational characteristics at the project location? ▪ 85th percentile speeds ▪ Average annual daily traffic ▪ Delay during and outside of peak periods – Reliability of operational performance (e.g., variability in travel time)? The preceding questions serve as a guide for practitioners to characterize and document the project context their design (or designs) should fit within. The full set of questions may not always be applicable to a given project or scenario, and in some instances additional considerations or unique attributes will surface as key defining characteristics of a project. All project participants have the flexibility to consider and define the context for their design environment. 5.2.2 Intended Outcomes The step of identifying the intended project outcomes (during the project initiation phase) helps focus the performance measures and evaluation criteria on the characteristics reflecting the core purpose of the project investment. Transportation improvement projects tend to be identified as needed based on any one or combination of the following activities (project catalysts): • Long-range planning activities by an agency • An acute operational deficiency (e.g., congestion in the peak period) • Community concerns (e.g., pedestrian crossing needs near schools, speeds on neighborhood streets) • Severe recent crash events • Private development (e.g., opportunity to attract employers and/or accommodating new trip generators)

48 Performance-Based Analysis of Geometric Design of Highways and Streets At the root of such a project catalyst is the purpose of the project and a desired outcome from the investment. The desired outcomes help define design controls leading to appropriately selected criteria to meet targeted design and operational performance. Once the desired out- come is articulated, performance categories and specific performance measures can be selected to evaluate how well the project or decisions made within the project’s development will help make progress toward the intended outcome. The results from the intended outcomes step are the identification of the following: 1. The primary and supplemental target audience for the project 2. The project objectives and intended outcomes 3. Performance measures to evaluate progress toward the intended outcomes Section 3.3.2 describes geometric design performance categories (accessibility, mobility, quality of service, reliability, and safety) that influence and are influenced by geometric design elements and their characteristics. These transportation performance categories have corre- sponding performance measures that can help a designer or analyst compare various geometric solutions and guide decision making based on how well a project or geometric element meets project objectives and intended outcomes. The information presented in Section 4.4 can be used to help inform performance category and measure selection. Results 1 and 2 listed previously can have a direct impact on the performance categories and associated measures selected to evaluate the decisions made in the project’s development and the project as a whole. These directly influence project design controls and resultant criteria. For example, a project to improve transit riders’ experience along a corridor (i.e., the desired project outcome is improved transit rider experience) would include performance categories such as quality of service, accessibility, and safety. These could result in performance measures such as street crossing distance for pedestrians, proximity of controlled or marked pedestrian crossings to transit stops, and other similar attributes that would influence the quality of service for transit riders as they access and use the transit service. Potential solutions would be sure to include design parameters to accommodate transit vehicles as a key design vehicle and modal considerations along and across the roadway (e.g., crossing distances for pedestrians, median types, operating speeds, and pedestrian and bicyclist accommodation). Therefore, Results 1 and 2 (i.e., identifying the target audience and intended project outcome) help inform the range of performance categories and the specific performance measures selected to evaluate design deci- sions within the project. The following items should be considered when working toward the three results previously listed (each user has the flexibility to consider items related to his or her unique project needs.): 1. When identifying the primary and supplemental target audience, consider the following: • Who is being served by the project? – Specific road users such as pedestrians, bicyclists, motorists, freight haulers, agricultural users, logging users, industrial users, commuter traffic, tourists/visitors – Specific community groups such as local businesses, targeted employers, a neighbor- hood, a school or school district, a community center • What are the planned land uses in the vicinity of the project area? What are they now and how do they need to be served? How might they change in the future? • What is the purpose and function of the street and/or intersection at the time the project is expected to be completed? • What road users are likely to desire the use of the highway or street given the role it plays in the network and the existing and planned land uses? • What are the existing and anticipated future socio-demographics of the population adjacent to and in the vicinity of the existing or planned street?

Process Framework 49 • What are the existing perceived or actual shortcomings of the highway or street? • How do the transportation elements best fit within the existing and future land use context? 2. When identifying the project objectives and intended outcomes, consider the following: • What is the project trying to achieve? – What is the broader project purpose or catalyst? ▪ For example, to facilitate economic development, improve livability, make progress in sustainability, enhance safe routes to school for children, attract new employers and jobs, improve air quality – What are the engineering performance categories influencing the broader project purpose or catalyst? ▪ For example, accessibility—access to destinations, access to facilities (bicycle lanes, sidewalks, transit service) ▪ For example, mobility—average travel time, mobility, average travel speed, inferred speed ▪ For example, quality of service—improve (or provide) facilities for pedestrians, bicy- clists, and transit riders; improve travel experience for road users; ability to serve or design vehicles ▪ For example, reliability—variability in travel time ▪ For example, safety—number of crashes, crash severity, users feeling safe 3. When identifying performance categories and performance measures that apply to the intended project outcomes, select the following: • Performance categories and measures that evaluate the actual performance of interest, examples: – Accessibility—identify access for whom and to what. For example: ▪ Heavy vehicles to/from industrial area and freeway ▪ Residents from residential area to/from regional parks ▪ Pedestrians to/from origins/destinations and transit service – Mobility—consider average travel time, delay, inferred speeds, target speeds – Quality of service—consider for whom, condition of facilities, ease of travel for user, direct traveler experience – Reliability—identify road user and corridor of interest, consider variability in travel time under range of potential operating conditions (e.g., incidents, weather events, recurring congestion) – Safety—consider expected crash frequency and severity, management of conflict points, speed as related to crash severity • Select a manageable number of performance measures to apply to alternatives • Select performance measures that can be assessed (qualitatively or quantitatively) given the project data and scope Some design decisions will occur in later stages of the project development process where the intended outcomes of the project were previously identified. In such instances, the purpose of revisiting the previously defined intended outcomes is to remind designers and the project team of the collective project purpose to help keep design decisions on track to support the overarch- ing intended outcome of the investment. A project originally intended to reduce the severity and number of crashes on a high-speed rural highway should not unintentionally evolve into a project with design elements promoting higher speeds (e.g., larger radii, increased supereleva- tion). A project originally intended to improve pedestrian and bicycle facilities should not evolve to sacrificing bicycle lane and/or sidewalk width to provide more auto capacity. The resulting performance of a roadway or intersection due to design decisions should be evaluated against the original intended project outcomes. The purpose of revisiting the previously defined intended outcomes is to remind designers and the project team of the collective project purpose to help keep design decisions on track to support the overarching intended outcome of the investment.

50 Performance-Based Analysis of Geometric Design of Highways and Streets In some projects, solutions may evolve to a configuration or magnitude outside the intent of the original project outcomes. In these rare cases, project participants have had to re-evaluate and agree upon the intended project outcomes. This can result in costs exceeding project budgets and project implementation delays. The principles of context-sensitive solutions are based on identifying and agreeing on overall project outcomes early in the project. The risk of project overruns and delays may be reduced by being sure geometric solutions are geared to address identified project needs. Performance-based outcomes help all parties develop and support appropriate project solutions. 5.3 Concept Development Concept development primarily consists of developing potential solutions to address the intended project outcome and project issues at hand. Concept development could also include evaluating discrete design decisions of a geometric element or configuration. Early in a project’s development, concept development will consist of identifying and developing overarching alternatives. This could include alternative intersection forms, roadway align- ments, roadway cross sections, interchange forms, or similar broader project alternative solutions. As a project progresses toward final design, the concept development will be more focused on solving a specific issue. This could include adjusting specific horizontal curves to reduce the amount of cut or fill needed to construct or modify the roadway shoul- der width and side slope to reduce the impact of the roadway prism in an environmentally sensitive area. The steps in this phase of understanding the geometric influences will help inform and guide the range of potential solutions. In each of the instances just noted, there are (1) geometric features that will influence the performance of the ultimate roadway facility and (2) a set of potential solutions whose result- ing performance can be evaluated to help determine which solution is preferred. The two steps within the concept development phase consist of identifying the geometric features influencing performance outcomes and developing a set of solutions to be evaluated. Each is discussed in the following subsections. 5.3.1 Geometric Influences This step helps identify geometric influences, which are the geometric characteristics or decisions that can influence a project’s performance as it relates to the categories of accessibility, mobility, quality of service, reliability, and safety. It also includes geometric characteristics or decisions influ- enced by the desired performance of a project. The focus of this step is to identify the following: 1. Geometric characteristics or decisions (e.g., type of intersection control) that have the potential to influence a project’s performance 2. Geometric characteristics or decisions influenced by the desired performance of a project The purpose of identifying these geometric characteristics and decisions is to create an aware- ness of the potential performance impacts design decisions have as project solutions are being considered. The information presented in Sections 4.3 and 4.4 are provided to help practi- tioners identify the key geometric elements critical to a given project’s or potential solution’s performance. For example, intersection traffic control is a geometric design decision having the ability to influence a project’s performance as it relates to safety (as well as other performance cat- egories). Single-lane roundabouts have been consistently found to have fewer total and severe crashes than two-way, stop-controlled intersections. This is an example of a geometric design decision influencing a project’s performance. Should a particular location not be compatible

Process Framework 51 with implementing a roundabout, the designer may evaluate the performance qualities of other intersection forms and use performance categories and measures to help differentiate between concepts or design alternatives. Using the same basic example as above, further along in the project development process (e.g., 15% design), the roundabout-specific design features will be influenced by the need to have entry speeds of about 20 mph. This desired speed performance will directly influence the approach and entry geometry to the roundabout. This is an example of a performance measure influencing geometric design decisions. Section 4.4 presents a series of tables and information to help identify which geometric features on corridors and segments and at intersections and interchanges may influence performance categories of accessibility, mobility, quality of service, reliability, and safety—and, in turn, which performance measures may influence geometric characteristics and decisions. The information in Section 4.4 can be used to identify key geometric characteristics for achieving the desired project outcomes; this is useful information in developing potential solutions (see next subsection) that make progress toward the intended project outcomes. 5.3.2 Potential Solutions Developing potential solutions is the core activity within the concept development phase. Potential solutions can be broad-based concepts early in the development of a project or more detailed, project-specific solutions to address a specific need, issue, or challenge. Broad-based concepts commonly explored early in a project’s development (e.g., alternatives identification and evaluation) include geometric design considerations such as the number of through lanes on an arterial, intersection traffic control options, intersection lane configurations, presence of a raised median, and other similar overarching design characteristics. In later stages of the project development process (e.g., preliminary design, final design), more detailed decisions are made, and in some instances, alternative design decisions are considered to address a project need, issue, or challenge. A designer may develop alternative solutions to consider, for example, different roadway shoulder widths and side slopes to reduce the impact of the roadway prism in an environmentally sensitive area. In a more urban context, designers may develop alternative solutions to consider the performance tradeoffs of narrowing vehicle lanes to provide bicycle lanes, widen sidewalks, or create a transit-only lane. Regardless of where a project is in the project development process, designers, engineers, planners, and other transportation professionals go through a process of considering alternative solutions to address a specific need, issue, or challenge. The intent of the potential solutions step is to develop those potential solutions with a specific awareness of what has been learned in the previous activities—with a specific awareness of the following: • Project context • Intended outcomes from the project and the performance categories and measures reflecting those desired outcomes • Geometric characteristics and decisions with the greatest ability to influence the degree to which the project (or ultimate design) achieves the desired outcomes Within the potential solutions step, designers, engineers, planners, and transportation pro- fessionals may use the information they have learned and assembled in the previous steps (i.e., project context, intended outcomes, geometric influences) in combination with the prevailing design guidance applicable to their project to develop alternative solutions addressing the project need, issue, or challenge.

52 Performance-Based Analysis of Geometric Design of Highways and Streets Potential design guidance applicable to a project can include a vast range of resources. For the purpose of illustrating some of the resources and examples of the range and diversity, these documents include the following: • AASHTO A Policy on the Geometric Design of Highways and Streets (1) • NCHRP Report 672: Roundabouts: An Informational Guide, Second Edition (2) • State department of transportation design manuals or design guidance • Manual on Uniform Traffic Control Devices (3) • FHWA Signalized Intersections: Informational Guide (4) • ITE Freeway and Interchange Geometric Design Handbook (5) • NCHRP Report 687: Guidance for Ramp and Interchange Spacing (6) • NCHRP Report 613: Guidelines for the Selection of Speed Reduction Treatments at High-Speed Intersections (7) • FHWA Speed Concepts: Informational Guide (8) • Other industry-published design guidance The design guidance used to develop the potential solutions should generally be used as guidance and not absolutes. Designers, engineers, planners, and transportation professionals should consider, but not necessarily be constrained by, the guidance; in the following phase— evaluation and selection—designers, engineers, planners, or transportation professionals will have the opportunity to evaluate the impact of their design decisions on a project’s performance. This will help determine which alternatives perform at a level to meet the desired outcomes (or project requirements). Engineers are sometimes concerned about tort liability and lawsuits. Having a documented process identifying the intended outcomes, design choices considered, and influences leading to the ultimate design choices is one of the best ways to support legal questions or challenges to design decisions. In some instances, transportation professionals may find some of the geometric elements in their preferred alternative do not meet the geometric criteria outlined in the prevailing design guidance and, in those instances, design exceptions or variances may be needed depending on the governing jurisdiction. Designers, engineers, planners, and transportation professionals should not assume a design exception is negative, nor that it is necessarily a reflection of a project’s potential safety performance. The purpose of the evaluation and selection phase (discussed in the follow subsection) is to evaluate the anticipated performance of a project (in terms of acces- sibility, mobility, quality of service, reliability, and safety) and to learn whether a design excep- tion or variation from published design criteria has a positive or negative impact on achieving the project’s desired outcome. In other words, performance-based analysis of geometric design can support design variance or exception activities. 5.4 Evaluation and Selection The evaluation and selection phase is where designers, engineers, planners, and transporta- tion professionals directly integrate performance-based analysis to further refine the solutions they developed in the previous phase. Ultimately a design element or configuration is selected based on these efforts. The primary steps are to estimate performance and financial feasibility of potential project or design choices. The possible outcomes from this phase are (1) a return to the concept development phase for further solution development or refinement or (2) a selected project. To reach one of those two outcomes, the designer, engineer, planner, or transporta- tion professional will evaluate the performance of a project relative to the previously identified performance categories and associated measures. They will consider the financial feasibility of each alternative and decide if there is an alternative that sufficiently meets the project’s intended outcome and is financially feasible. The processes for evaluating the performance of the project Having a documented process identifying the intended outcomes, design choices considered, and influences leading to the ultimate design choices is one of the best ways to support legal questions or challenges to design decisions.

Process Framework 53 and assessing its financial feasibility, and guidance for deciding when to select an alternative or further refine alternatives are discussed in the following subsections. 5.4.1 Estimated Performance and Financial Feasibility The following subsections discuss steps to estimate performance of design choices and consider the financial feasibility of design alternatives. The subsections conclude with a discussion on interpreting results from the estimated project performance and financial feasibility evaluation activities. 5.4.1.1 Estimated Project Performance Estimating or evaluating a project’s likely performance during this step requires an awareness of the resources available to quantify specific performance measures or qualita- tively describe the anticipated effect of a given roadway, intersection, or interchange design. For example, to evaluate the safety performance of a rural two-lane roadway, a user must know that Chapter 10 of the Highway Safety Manual (9) presents information to predict the number and severity of crashes on a two-lane rural roadway based on its cross-sectional charac- teristics, horizontal alignment, vertical alignment, traffic volume, and crash history. Therefore, Section 4.4 contains table summaries to help identify the available resources for evaluating the performance of roadway segments, intersections, and interchanges as related to accessibility, mobility, quality of service, reliability, and safety. Estimating a project’s performance is not intended to be a long or arduous process. Many of the performance-based resources available are supplemented with spreadsheet or software tools to help expedite their application, and some include graphical representations or table sum- maries of the relationships to provide guidance early in a project’s development. For example, NCHRP Report 672: Roundabouts: An Informational Guide, Second Edition (2) includes a table summary of volume ranges to help determine the approximate number of lanes required for a roundabout (see Exhibit 5-2). With respect to evaluating the performance of a design, designers, engineers, planners, and transportation professionals should be aware of the following critical elements: • Selecting the evaluation resource or tool most appropriate for the stage in the project develop- ment process. More detailed and refined evaluations will likely only be possible at later stages in the project development process when more information is available. – For example, if considering alternative roadway segments in the alternatives identification and evaluation stage of the project development process, comparing the relative safety and Volume Range (sum of entering and conflicting volumes) Number of Lanes Required 0 to 1,000 vehicles/hour • Single-lane entry likely to be sufficient 1,000 to 1,300 vehicles/hour • Two-lane entry may be needed • Single-lane entry may be sufficient upon more detailed analysis 1,300 to 1,800 vehicles/hour • Two-lane entry likely to be sufficient Above 1,800 vehicles/hour • More than two entering lanes may be required • A more detailed capacity evaluation should be conducted to verify lane numbers and arrangements Exhibit 5-2. Planning-level analysis of roundabout lane needs (2, Exhibit 3-14).

54 Performance-Based Analysis of Geometric Design of Highways and Streets mobility performance of two-lane, two-lane divided, three-lane, and four-lane facilities is sufficient. In later stages, the impact of the specific horizontal alignment (e.g., curve radii, superelevation) on performance would be considered. – Specific to safety performance, this difference in level of detail could mean that, in earlier stages of the project development process, consulting graphs or charts from the Highway Safety Manual is sufficient to understand the crash performance tradeoffs, while a more detailed tool such as the Interactive Highway Safety Design Model (10) would be needed to assess the performance of decisions later in the design process. • Selecting the evaluation resource or tool most applicable or transferable to the project context. – For example, when evaluating a rural two-lane roadway, using resources and tools applica- ble to rural two-lane roadways. While this may seem obvious, there may be some instances when a resource is not available for a specific context but is for another context. Using a tool applicable to multilane highways to evaluate the performance of a rural two-lane roadway will not yield reliable results. – In other instances, selecting a tool or resource to evaluate performance of a project may be related more to the surrounding context of the roadway. For example, a state highway passing through a rural community town center—while classified as a regional, major arterial—is more likely functioning as a rural main street needing to accommodate pedestrians, bicycles, and possibly transit service as well as motor vehicles. It also is probably a place for on-street parking and is serving as the front entrance/access to local businesses. In this context, down- town urban-type performance measures and tools may be more appropriate to capture the multimodal, slower speed, and access needs of the roadway. Once the appropriate evaluation tool and resource is selected for the given project and per- formance measures, designers, engineers, planners, and transportation professionals can apply the tool or resource to assess the project alternatives’ relative performance. The results for each alternative solution can be summarized in tabular summaries or figures depending on the scope of the project and the alternatives. Exhibit 5-3 is one example of how the information can be summarized. It illustrates alternative horizontal curve radii being considered for a rural two-lane roadway. The intended project outcome is to reduce the number of crashes, while minimizing the cut and fill required to realign the roadway. The posted speed is 45 mph. Project Example 2 in Chapter 6 presents the full performance-based application process for the project. From the information summarized in Exhibit 5-3, it is clear Alternative 2 provides the greatest predicted safety benefit (four total crashes per year) while creating an inferred speed closest to the posted 45 mph. However, it does not result in the least amount of cut/fill for the project. This illustrates one of the many potential tradeoffs in meeting performance characteristics that may have relationships counter to each other. In this instance, larger curve radii tend to be associated Alternative Safety Performancea Mobility Performanceb Average Cut or Fill Required per Station No Project 13 total crashes/year Inferred Speed of 15 to 55 mph 0 yd 3 1 – Minimal 11 total crashes/year Inferred Speed of 15 to 55 mph 100 yd 3 2 – Ultimate 4 total crashes/year Inferred Speed of 60 to 80 mph 700 yd 3 3 – Practical 7 total crashes/year Inferred Speed of 35 to 40 mph 200 yd 3 4 – Subultimate 6 total crashes/year Inferred Speed of 60 to 80 mph 450 yd 3 aExpected (average) annual total crashes per year bInferred speed of horizontal curves within study area Exhibit 5-3. Example summary of evaluation results.

Process Framework 55 with fewer crashes but in mountainous or rolling terrain often result in more cut or fill and therefore higher project costs. To help further inform these types of decisions where tradeoffs between performance must be made, incorporating the financial feasibility or cost effectiveness of a project can be helpful in either selecting an alternative or refining one or more alternatives for continued analysis. The following subsection discusses sample approaches for considering the financial feasibility of the project alternatives. 5.4.1.2 Financial Feasibility Financial feasibility assessments of a project or set of alternatives during this step can be useful in helping to prioritize investments and the relative effectiveness of potential projects. This section highlights three basic approaches for considering the financial feasibility of an alternative: • Total construction and maintenance cost of the alternative • Cost effectiveness of the alternative • Benefit/cost ratio of the alternative The transportation profession includes other published documents that are more compre- hensive resources for financial feasibility (i.e., economic appraisal) than this report is intended to be. For more detailed guidance and information about how to specifically conduct financial feasibility calculations, please refer to resources such as AASHTO’s User and Non-user Benefit Analysis for Highways, Third Edition (11). For a given alternative, the total construction and maintenance cost can be estimated and compared to the funding available. If the alternative meets the desired performance measures based on the analysis in the evaluation phase and funding is available to implement it, then in some instances this may be a sufficient level of consideration for the financial feasibility of the alternative. In other instances, funding and resources may be limited and, therefore, a greater level of financial analysis is needed to determine the value provided by each alternative relative to the investment made to implement the alternative. One approach to estimate the relative value of an investment is to calculate the cost effective- ness of each alternative. This is achieved by estimating the cost of constructing and maintain- ing each alternative and comparing that to the preferred performance measure. For example, alternatives intended to reduce crashes at a location could be prioritized based on their relative cost effectiveness at reducing crashes. If Alternative A is estimated to reduce five crashes per year at an annual cost of $2,000, then its cost effectiveness is $400 per mitigated crash. Alternative A could then be ranked or prioritized for further consideration based on how other alternatives perform. Project Example 1 in Chapter 6 employs this type of financial feasibility assessment. A second approach for estimating the relative value of an investment is to use a benefit/cost ratio. Benefit/cost ratios greater than 1.0 indicate the benefits outweigh the costs of the alterna- tive and therefore are a reasonable potential investment. In instances where multiple alternatives return a benefit/cost ratio greater than 1.0, an incremental benefit/cost ratio may be used to directly compare the incremental value that one alternative provides over the other. A key con- sideration for calculating benefit/cost ratios is this approach requires converting the engineering performance measures to a monetary value. For example, the estimated change in crashes, delay, or other similar metrics would need to be converted to a dollar amount for comparison to the project costs. Resources such as AASHTO’s User and Non-user Benefit Analysis for Highways, Third Edition (11) provide guidance on best practices for conducting benefit-cost assessments.

56 Performance-Based Analysis of Geometric Design of Highways and Streets 5.4.1.3 Interpreting Results from the Estimated Project Performance and Financial Feasibility The results from the steps to estimate the project performance and financial feasibility of the alternatives are intended to inform the geometric design decisions being made. Design- ers may choose alternatives that are not necessarily the most cost effective or even the highest performing relative to the preferred performance measure. The example scenario presented in Exhibit 5-3 presented a solution that may have best met safety and speed performance objec- tives but that may not be selected because of its anticipated cost and the cut/fill impacts on the surrounding area. The ultimate design decisions may also be influenced by additional qualita- tive factors (e.g., solutions consistent with a community’s rural heritage) that cannot be cap- tured with quantitative performance measures or financial assessments. The foregoing steps are intended to help designers, engineers, planners, and transportation professionals to be more aware of the performance tradeoffs their decisions have and how that affects the overarching intent of their project. The ultimate design decisions still reside at the discretion of the designer, engineer, planner, or transportation professional in charge of the project. Project decision mak- ing should include clear and complete documentation of the overall identification of intended outcomes and information highlighting the evaluation process and judgment used to make actual project design decisions. The following section presents considerations regarding when to consider selecting an alternative and when there may be value in refining and re-evaluating alternatives. 5.4.2 Selection Based on the results from the estimated performance and financial feasibility step, designers, engineers, planners, or transportation professionals will need to either select a preferred alternative or decide to further refine alternatives and re-evaluate their performance. The following are items to consider in making this decision: • Are the performance evaluation results making progress toward the intended project out- comes? Do the alternatives serve the target audience and achieve the desired objectives? – If no, revisit the concept development stage, revise the alternatives, and re-evaluate the performance. • Can reasonable adjustments be made to the geometric design elements most significantly influencing project performance? – If yes, consider refining one or two of the top performing alternatives and re-evaluating them. • Do the performance measures help differentiate between the alternatives? – If no, consider adding or modifying the performance measures to help differentiate among the alternatives, or consider significantly modifying alternatives to better reflect desired performance. As noted previously, there may be other external factors or qualitative performance measures driving the decision to select a preferred alternative or further refine and re-evaluate alternatives. The preceding questions are intended to help generate thought and considerations for how best to advance a project to the next stage in the project development process. 5.5 Environmental Review Process This section discusses how the performance-based analysis framework presented in the pre- vious sections can be incorporated into a basic environmental review process. For this research effort, the environmental review process is defined as three levels based on NEPA (12). Many

Process Framework 57 states have adopted their own variation for non-federal projects. State Environmental Policy Act processes may use different terms; however, the state processes generally follow those of NEPA. The NEPA review processes include the following: 1. Environmental Checklist 2. Environmental Assessment (EA) 3. Environmental Impact Statement (EIS) The level of technical analysis, documentation, and review increases as a project progresses from an Environmental Checklist to an EA or EIS. The following subsections discuss how performance-based analysis can be useful within each level of evaluation. 5.5.1 Environmental Checklist An Environmental Checklist enables state agencies to screen projects relative to their potential for environmental impacts. Projects that “pass” the checklist qualify for a Categorical Exclusion (CE). A CE enables a project to move forward in its development without the need for additional environmental analysis, documentation, or review by the state or FHWA. Typically, a CE can be obtained if each of the following items is met (12): • The action does not have significant environmental impacts as defined in 23 Code of Federal Regulations (CFR) 771.117(a). • The action does not involve unusual circumstances as defined in 23 CFR 771.117(b). • The action does not involve: – Right-of-way acquisition – Use of protected properties as defined by federal or state law – Permits from U.S. Coast Guard or Army Corps of Engineers – Wetlands – Encroaching on a floodway or base floodplain – Impacts to a river designated as part of the National System of Wild and Scenic Rivers – Changes to access control – Constructing temporary roads, detours, or ramp closures – Known hazardous materials or previous land uses with potential for hazardous materials • The action conforms to the Air Quality Implementation Plan. • The action is consistent with a state’s Coastal Zone Management Plan. • The action is in an area with no federally listed endangered or threatened species or critical habitat. The level of analysis and documentation needed to complete an Environmental Checklist is usually confined to existing data or data readily available or observable in a field visit. The performance-based analysis framework can be used to explore and consider project alter- natives or adjustments to enable a project to be eligible for a CE. In some instances, by adjusting a preferred alternative’s alignment or cross section, a designer may find limited to no impact on safety and mobility (or other project performance measure) and may be able to avoid actions that would prevent the project from qualifying for a CE. Once a project qualifies for a CE, the performance-based analysis framework can continue to serve as a useful tool for developing and evaluating alternative design decisions. It can also serve as a framework for document- ing the project development process to support public outreach, facilitate coordination within and among partner agencies, and manage an agency’s risk related to tort liability. If the design requires a variance or exception, the performance-based analysis and results can support docu- mentation efforts. In summary, the performance-based analysis framework adds value to project development activities regardless of whether that project is being developed within or outside of an environmental review process.

58 Performance-Based Analysis of Geometric Design of Highways and Streets If a project does not qualify for a CE, the level of environmental analysis, documentation, and review progresses to an EA. 5.5.2 Environmental Assessment An EA is performed when the significance of impacts of a project is uncertain; an EA helps to determine whether a project will result in significant environmental impacts. If significant impacts are found to occur while developing or reviewing the EA, then an EIS is needed. The purpose of an EA is as follows: • To briefly provide sufficient evidence and analysis to determine whether there is a significant impact • To aid in an agency’s compliance with NEPA when an EIS is not needed • To facilitate preparation of an EIS, if one is needed An EA must include a brief discussion of the project need, alternative solutions, docu- mentation of the environmental impacts of the alternatives, and a list of people and agencies consulted (12). In the process of preparing an EA, the project initiation phase of the performance-based analysis framework can serve as a useful resource in developing a clear, sound, and concise project purpose and need statement. The concept development and evaluation and selection phases of the performance-based analysis framework are great resources for developing alter- natives that minimize the potential for environmental impacts. And, the performance-based analysis framework provides a means for documenting the alternatives considered, their respec- tive performance, and the ultimate finding of significant impacts or finding of no significant impact (FONSI). A FONSI enables the project to move forward without additional environ- mental analysis, documentation, or review. A finding of significant impact requires additional environmental analysis, documentation, and review in the form of an EIS. 5.5.3 Environmental Impact Statement An EIS is required for major federal actions (e.g., major transportation capital projects receiv- ing federal funding) significantly affecting the quality of the human environment. It is consid- ered a full disclosure document detailing the process employed to develop the project, including the range of reasonable alternatives considered and analysis of the potential impacts from the alternatives. It also demonstrates compliance with other applicable environmental laws and executive orders. The EIS process consists of a Notice of Intent to initiate the process, a draft EIS, final EIS, and a Record of Decision (ROD). Public involvement and agency coordination are present through- out the EIS process. The draft EIS provides a detailed description of the proposed project, the purpose and need, reasonable alternatives, affected environment, and analysis of anticipated beneficial and adverse environmental effects of the alternatives. The final EIS addresses the com- ments received on the draft EIS and identifies the preferred alternative. The ROD identifies the selected alternative, presents the basis for the decision, identifies all of the alternatives consid- ered, specifies the “environmentally preferable alternative,” and provides information on the adopted means to avoid, minimize, and compensate for the environmental impacts. The performance-based analysis framework can benefit practitioners in developing a draft EIS, selecting a preferred alternative in the final EIS, and identifying the means to avoid and minimize environmental impacts. The project initiation phase can be used to develop a clear and focused project purpose and need statement. The concept development and evaluation and

Process Framework 59 selection phases can be used to develop reasonable alternatives that perform to a level to fulfill the project’s purpose and need while avoiding or minimizing environmental impacts. The evalu- ation and selection phase can also be used to help identify the preferred alternative. The overall performance-based analysis framework can also be used to facilitate the comprehensive docu- mentation needed within the EIS process. 5.6 Summary This chapter presents the performance-based analysis application framework and provides a description of each phase and step within each phase. This chapter also noted where informa- tion from previous chapters can be integrated into the framework to facilitate its application. Chapter 6 presents project examples illustrating how the framework can be applied to differ- ent projects at different stages within the project development process. A brief overview of the project examples in Chapter 6 follows: • Project Example 1 evaluates the safety performance of alternative intersection improvements on a rural two-lane highway. The intent of the project is to reduce the frequency and severity of crashes at the study intersection. • Project Example 2 considers the safety and mobility performance of alternative roadway alignments (e.g., tradeoffs of different horizontal curve characteristics) on a rural two-lane roadway. The intent of the project is to reduce the frequency and severity of crashes along the study corridor, while maintaining reasonable mobility for local residents and minimizing the cost of the ultimate project. • Project Example 3 evaluates the safety, mobility, accessibility, reliability, and quality of service performance of alternative roadway cross sections for a suburban arterial. The project is focused on converting the auto-oriented arterial into a roadway capable of serv- ing a wider range of modes (e.g., pedestrians, bicyclists) without needing to acquire addi- tional right-of-way. • Project Example 4 analyzes the safety, mobility, and reliability performance of alternative roadway shoulder widths and side slopes on a rural collector. The project’s intent is to improve safety, mobility, and reliability performance, while minimizing impacts to the adjacent envi- ronmentally sensitive areas. • Project Example 5 assesses the performance tradeoffs between safety, quality of service, and accessibility for alternative alignment and cross sections of a new urban collector intended to serve large vehicles accessing an industrial area as well as bicyclists and recreational travelers accessing a regional park. • Project Example 6 considers safety and mobility of alternative interchange forms in a rural area. The study area is evolving from rural to suburban. The existing grade-separated regional highway is expanding its grade-separated/access-controlled characteristics farther out from the urban core. 5.7 References 1. American Association of State Highway and Transportation Officials. A Policy on Geometric Design of High- ways and Streets. Washington, D.C.: 2011. 2. Rodegerdts, L., J. Bansen, C. Tiesler, J. Knudsen, E. Myers, M. Johnson, M. Moule, B. Persaud, C. Lyon, S. Hallmark, H. Isebrands, et al. NCHRP Report 672: Roundabouts: An Informational Guide, Second Edition. Washington, D.C.: Transportation Research Board of the National Academies, 2010. 3. Federal Highway Administration. Manual on Uniform Traffic Control Devices. Washington, D.C.: 2009. 4. Federal Highway Administration. Signalized Intersections: Informational Guide. Washington, D.C.: 2004.

60 Performance-Based Analysis of Geometric Design of Highways and Streets 5. Institute of Transportation Engineers. Freeway and Interchange Geometric Design Handbook. Washington, D.C.: 2005. 6. Ray, B. L., J. Schoen, P. Jenior, J. Knudsen, R. J. Porter, J. P. Leisch, J. Mason, R. Roess, and Traffic Research & Analysis, Inc. NCHRP Report 687: Guidance for Ramp and Interchange Spacing. Washington, D.C.: Transporta- tion Research Board of the National Academies, 2011. 7. Ray, R., W. Kittelson, J. Knudsen, B. Nevers, P. Ryus, K. Sylvester, I. Potts, D. Harwood, D. Gilmore, D. Torbic, F. Hanscom, et al. NCHRP Report 613: Guidelines for Selection of Speed Reduction Treatments at High-Speed Intersections. Washington, D.C.: Transportation Research Board of the National Academies, 2008. 8. Federal Highway Administration. Speed Concepts: Informational Guide. Washington, D.C.: 2009. 9. American Association of State Highway and Transportation Officials. Highway Safety Manual. Washington, D.C.: 2010. 10. Federal Highway Administration. Interactive Highway Safety Design Model. Washington, D.C.: 2003. 11. American Association of State Highway and Transportation Officials. User and Non-user Benefit Analysis for Highways, Third Edition. Washington, D.C.: 2010. 12. US Department of Transportation, Federal Highway Administration Environmental Toolkit: http://www. environment.fhwa.dot.gov/projdev/docuceda.asp. Accessed: August 10, 2013.

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 785: Performance-Based Analysis of Geometric Design of Highways and Streets presents an approach for understanding the desired outcomes of a project, selecting performance measures that align with those outcomes, evaluating the impact of alternative geometric design decisions on those performance measures, and arriving at solutions that achieve the overall desired project outcomes.

This project has also produced a supplemental research materials report and a PowerPoint presentation.

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