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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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Suggested Citation:"Chapter 4 - Assessment." National Academies of Sciences, Engineering, and Medicine. 2021. Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges. Washington, DC: The National Academies Press. doi: 10.17226/26072.
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4-1 The assessment of A.I.I. alternatives for pedestrians and bicyclists is an integral part of the Intersection Control Evaluation (ICE) process and performance-based design. As noted in Chapter 1, the ICE process is carried out using two stages of evaluation, which are mirrored in this assessment approach. Even absent an ICE framework, the concepts in this chapter apply to the project development process in general. This chapter presents quantitative and qualitative techniques to establish initial design decisions and to evaluate the performance of alternatives. This chapter presents three major categories of assessment tools: • Facility design elements, used during Stage 1 to identify basic pedestrian and bicyclist facility types and routing; • Quantitative evaluation techniques, used during both Stages 1 and 2, to assess to quality of service and level of comfort; and • Design flags, used during Stage 2, to assess safety, accessibility, comfort, and operational aspects for each mode. The core of the assessment is the Design Flag method in Section 4.4. The evaluation criteria for determining which alternatives are selected for advancement to the next stage vary based on context and agency requirements, as well as other factors and are beyond the scope of this document. Exhibit 4-1 summarizes the assessment framework for pedestrian and bicyclist safety at A.I.I.s 4.1 Facility Design Selection – ICE Stage 1 At Stage 1, the overall footprint and feasibility of an intersection or interchange configuration are established for each alternative. Pedestrian and bicycle facilities need to be considered during this stage because they can directly affect the footprint and right-of-way needs for an alternative. The basic questions at this stage focus on the pedestrian and bicycle facilities needed and how each origin-destination movement will be served. In many respects, these are the same types of decisions being made for each origin-destination movement for motor vehicles. Also, a configu- ration can have poor viability for pedestrians, bicyclists, or both, even though it may be viable for motor vehicles. As a result, the assessments for pedestrians and bicyclists for each Stage 1 alternative are a vital part of the evaluation. Key questions for making initial decisions in Stage 1 for pedestrian and bicycle facilities are given in Exhibit 4-2. It may be desirable to have different types of facilities on the major and the minor streets to serve different functional purposes or to address different speed and volume characteristics. C H A P T E R 4 Assessment

4-2 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Exhibit 4-1. Overview of the assessment framework for pedestrian and bicyclist safety at A.I.I.s.

Assessment 4-3 It is critical in the design process to decide on the pedestrian and bicycle facility type early; the decision can directly affect overall right-of-way needs and many subsequent design decisions. For pedestrians, sidewalks should be sized depending on local context and functional classifica- tion (see Chapter 2). For bicyclists, the guidance in Chapter 3 should be considered to determine whether a separated bike lane or shared-use path is needed in the design. Failure to incorporate these design elements into early concept designs may make it difficult to provide for a safe walk- ing and riding environment in later stages of design. 4.2 Quantitative Performance Measures – ICE Stages 1 and 2 For motor vehicles, a planning-level quantification of performance measures can be per- formed using a spreadsheet tool similar to FHWA’s CAP-X tool (1), the Florida Department of Transportation’s adaptation of CAP-X (2), or the Virginia Department of Transportation’s VJuST tool (3), which screen alternatives based on automobile critical movement analysis and resulting volume-to-capacity (v/c) ratio. For pedestrians and bicyclists, various quantitative performance measures are available to assess pedestrian and bicyclist quality of service and level of comfort. This section summarizes these measures. 4.2.1 Pedestrian Level of Service (PLOS) The Pedestrian Level of Service (PLOS) tool in the HCM (4), quantifies the comfort expe- rienced by pedestrians when traversing street links and intersections and includes factors associated with many of the parameters described in Section 2.1.4. Exhibit 4-2. Stage 1 design questions. Decision Questions to Ask Facility type What general type of pedestrian facility will be provided on each intersecting street? What general type of bicycle facility (e.g., separated bicycle facility, on-street bicycle lanes, or shared-use path) will be provided on each intersecting street? Routing decisions How will each origin-destination route for pedestrians be routed through the intersection (e.g., around the perimeter, through the interior, etc.)? How much space and what design treatments are needed to enable this pedestrian routing? How will each origin-destination route for bicyclists be routed through the intersection (e.g., around the perimeter, through the interior, etc.)? How much space and what design treatments are needed to enable this bicyclist routing?

4-4 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges PLOS categorizes quality of service for pedestrians on an A to F scale, where PLOS A is excel- lent or very comfortable for pedestrians, and F is very poor, indicating a very uncomfortable experience for pedestrians. Exhibit 4-3 tabulates the effect that various PLOS inputs have on the PLOS score for street segments and signalized intersections, where a higher score worsens the PLOS rating of the link or intersection. The PLOS link score reflects the pedestrian’s perceived comfort when walking along a street link. The PLOS score for a link is improved (made more comfortable) by wider sidewalks and greater separation distance from adjacent motor vehicle traffic. The presence of a barrier at least 3 feet tall within the street buffer or on-street parking that is normally occupied improves the PLOS score. The PLOS model cannot measure pedestrian safety or security, nor has it been calibrated to a mix of signalized and unsignalized crossings that may be present at some A.I.I.s. The PLOS model has other shortcomings, such as yielding scores that are more desirable when pedestrian signals are not provided in favor of vehicular traffic signals. Designers should under- stand the effect of various inputs in the PLOS analysis and make informed decisions about factors that not only affect the score but also the expected comfort. Motor vehicle LOS is based on motorist delay, and facilities are typically designed to provide LOS C or D; however, because PLOS measures perceived comfort, it is not appropriate to compare or apply similar target values of LOS for motorists and pedestrians. PLOS values of A or B are desirable to provide a comfortable experience. Many of these design variables relate to conditions in an A.I.I. Wide sidewalks and street buffers are encouraged for A.I.I. locations, given the high speeds and motor vehicle volumes that some A.I.I.s accommodate and which degrade PLOS. In an A.I.I., effective walkway widths should be at least 10 feet or greater so as to accommodate the expected pedestrian demand. It is unlikely that on-street parking will be part of the A.I.I. design; therefore, it is recommended that a vertical barrier or greater separation between the motor vehicle travel lanes and sidewalk be considered to improve the quality of service for pedestrians. System Element Design Element Influence on PLOS Urban Street Segment Width of outside through lane, shoulder, bike lane, parking lane Greater width Better PLOS score On-street parking occupancy Greater parking occupancy Better PLOS score Street buffer width Wider buffer Better PLOS score Presence of continuous 3-ft minimum-height barrier within the street buffer Presence of continuous barrier Better PLOS score Sidewalk width Wider sidewalk Better PLOS score Adjacent motor vehicle flow per travel lane Higher motor vehicle flow Poorer PLOS score Adjacent motor vehicle speed Higher motor vehicle speed Poorer PLOS score Roadway Crossing Diversion of the pedestrian path (to reach a signalized crossing) Greater diversion distance Poorer PLOS score Travel time delay (due to signal control or gap acceptance) Greater delay Poorer PLOS score Exhibit 4-3. Influence of design factors on PLOS. Source: Adapted from HCM, Sixth Edition (4).

Assessment 4-5 A factor in calculating PLOS involves the delay experienced by pedestrians. When a delay is perceived as excessive, pedestrians are more likely to take risks in crossing a conflicting traffic stream. The threshold for what is deemed excessive is similar for signalized and unsignalized crossings. Waiting in uncomfortable locations, like narrow median refuges or narrow sidewalks adjacent to travel lanes, could contribute to a pedestrian’s willingness to engage in risk-taking behavior. At signalized crossings where pedestrians expect to wait no more than 10 seconds, they are more likely to comply with pedestrian signal indications. However, when the signal-based pedestrian delay exceeds 30 seconds, the incidence of noncompliance grows, and pedestrians are more likely to disregard signal indications and look for gaps to cross against the signal (4). Unsignalized intersections may be evaluated by determining pedestrian crossing delay as pedestrians wait for gaps in traffic or for motorists to yield and allow them to cross. Pedestrians crossing at unsignalized locations have a slightly higher tolerance for delay than those crossing at signalized locations, with risk-taking behavior more likely as delays exceed 30 seconds. As delay reaches 45 seconds or more, pedestrians are more likely to accept smaller gaps and attempt to cross within a gap insufficient for a safe crossing (4). 4.2.2 Bicycle Level of Service (BLOS) Bicycle Level of Service (BLOS) analysis is described in the HCM (4). The BLOS method produces a comfort rating for street segments and intersection crossings that reflects numerous factors, including curb lane widths, bike lane widths, traffic volumes and speeds, pavement surface conditions, the presence of heavy vehicles, and on-street parking. BLOS A represents the most comfortable conditions. The BLOS model does not measure bicyclist safety or security and is not designed to measure the comfort of physically separated bicycle facilities. Exhibit 4-4 shows the influence of design factors on BLOS. Motor vehicle LOS is based on motorist delay, and facilities are typically designed to provide LOS C or D; however, because BLOS measures perceived comfort, it is not appropriate to compare or apply similar target values of LOS for motorists and bicyclists; BLOS values of A or B are desirable to ensure a comfortable experience. BLOS was calibrated based on more confident adult bicyclists and so may overestimate the level of comfort perceived by many riders in the Somewhat Confident and Interested but Concerned groups. 4.2.3 Shared-Use Path Level of Service FHWA provides a Shared-Use Path Level of Service (SUPLOS) method to measure path user comfort based on the estimated number of passing maneuvers likely to occur along a shared-use path and potential for conflict (5). Communities use SUPLOS in several ways: • Setting benchmarks for SUPLOS on shared-use paths of varying classifications; • Assessing overall network performance of existing conditions; and • Assessing proposed designs to determine optimal shared-use path width and the need for separating path users. (SUPLOS values below C suggest that separating users should be considered.) SUPLOS was developed through a large research sample of shared-use paths in multiple locations around the country and represents many shared-use path conditions. The inputs for scoring are • Shared-use path width; • User volumes and speeds in different modes (actual, estimated, or projected); and • Presence of a centerline stripe.

4-6 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Generally, the scoring accounts for the “friction” between users of different modes—pedestrians, bicyclists, runners, in-line skaters, and child bicyclists—as they pass one another using the trail. This friction is influenced by (1) volume and (2) width for users to move around one another. Within the context of an A.I.I., the SUPLOS tool can be used to identify (1) whether a shared- use path (sidepath) will safely accommodate the expected volumes of pedestrians and bicyclists and (2) if these users should be separated by constructing a combination of sidewalks and separated bike lanes. If SUPLOS is projected to be C or lower, a wider shared-use path should be evaluated or the provision of distinct facilities for each of these user groups should be considered. 4.2.4 Bicycle Level of Traffic Stress (LTS) Level of Traffic Stress (LTS) addresses deficiencies in the Bicycle LOS method (6). Unlike BLOS, which is calibrated to the confident bicyclist, LTS is based on the experiences of a wider range of bicyclists, including those less confident riding with or near motor vehicle traffic. The LTS method considers bicyclists’ varying confidence levels and integrates a suite of design parameters (such as bike lane width, motor vehicle speeds and volumes, and the likelihood of bike lane blockage) to develop a numerical rating for the comfort of a street segment. Scores System Element Design Element Influence on BLOS Network Link/ Segment Width of outside through lane, shoulder, bike lane, parking lane Greater width Better BLOS score On-street parking occupancy Greater parking occupancy Poorer BLOS score Adjacent motor vehicle flow per travel lane Higher motor vehicle flow Poorer BLOS score Adjacent motor vehicle speed Higher motor vehicle speed Poorer BLOS score Adjacent heavy vehicle percentage Higher heavy vehicle percentage Poorer BLOS score Pavement quality Better pavement quality Better BLOS score Number of intersecting side streets and driveway approaches (access points) More intersecting access points Poorer BLOS score Signalized Intersection Curb-to-curb width of the street being crossed Greater crossing width Poorer BLOS score Total combined left-turn, through, and right-turn vehicular demand flow rates per total travel lanes Greater vehicular demand Poorer BLOS score Width of outside through lane, shoulder, bike lane, parking lane Greater width Better BLOS score On-street parking occupancy Greater parking occupancy Poorer BLOS score Exhibit 4-4. Influence of design factors on BLOS. Source: HCM, Sixth Edition, Chapters 18 and 19 (4).

Assessment 4-7 range in integer values from 1 to 4, with more stressful conditions on the higher end of the range (LTS 3 or LTS 4). These scores loosely correspond to the three types of bicyclists, with all groups preferring LTS 1 bikeways and only the more stress-tolerant riders willing to use LTS 3 or LTS 4 facilities. Bicycle facilities that are wider, separate bicyclists from high-speed traffic, and have signal- ized treatments at crossings and intersections will typically receive lower LTS scores (indicating higher comfort), attracting a wider variety of users, including those who are less confident. In high-speed environments like many A.I.I.s built to date, it will be difficult to achieve low-stress bicycle facilities that are comfortable for all users without building shared-use paths (sidepaths) or high-quality separated bike lanes. 4.2.5 Other Quantitative Performance Measures Performance measures were examined under NCHRP Project 07-25 as either direct assess- ments of the performance of pedestrian and bicyclist facilities or as quantifiable surrogates. These are documented in the NCHRP Project 07-25 final report and are as follows: • Fastest path vehicle speed assessment, • Sight distance calculations, • Safety and conflict assessment, and • Accessibility assessment. 4.3 Operational Analysis – ICE Stage 2 In ICE Stage 1, the geometry of the intersection for each alternative has been relatively generic, with basic initial decisions about needed travel lanes for motor vehicles and types and routing of pedestrian and bicycle facilities. In ICE Stage 2, more details are developed in each of the remaining alternatives, and the operational needs for each user group are used to determine the initial geometry. At most traditional intersections, the crossing options for pedestrians and bicyclists are generally limited to one or two possible configurations; however, some A.I.I.s can have several possible crossing configurations. An operational analysis of the travel time and delay experi- enced by pedestrians and bicyclists, conducted in parallel with a similar analysis for motorists, will help to assess the most efficient routing for each mode. As routings become less efficient, it becomes increasingly likely that some pedestrians and bicyclists will cross in undesignated locations they perceive to be more efficient. These undesignated locations present a potential safety risk, because the design features in these undesignated locations may not be optimal for crossing, and motorists may not be expecting pedestrians and bicyclists in those locations. Also, these undesignated locations do not have the features to be accessible to all people. The operational analysis for each alternative should be appropriate for the context and com- plexity of the location. It should consider the effect of cycle length, phase sequence, and phase durations on each key pedestrian and bicyclist movement. Delays incurred by pedestrians and bicyclists should be considered concurrently with those incurred by motor vehicles and should be consistent with the context of the location. Analyses, sometimes, may be feasible with ana- lytical methods in the HCM (4). Sometimes, a simulation may be a better tool for assessing travel time and delay for each mode, particularly in cases of higher pedestrian and bicyclist volumes or more complex routings. Further discussion of these operational aspects is presented in Chapter 5 and the specific chapters for each A.I.I.

4-8 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 4.4 Design Flag Assessment As a surrogate for quantitative performance measures, performance measures—also known as design flags—can help identify potential safety, accessibility, operational, or comfort issues for pedestrians and bicyclists. A design flag does not necessarily represent a fatal flaw for an alterna- tive; rather, it presents a design issue that should be addressed in the iterative development and evaluation of the alternative. Some design flags depend on signalization decisions. Before a full signal design, an analysis should be conducted with the best information available. These design flags are not unique to A.I.I.s, as they may also apply to traditional intersections and interchanges. This guidebook encourages the use of design flags in evaluating and designing pedestrian and bicycle facilities for each alternative, whether traditional or A.I.I. The treatment guidance in this guidebook is intended to assist with both traditional intersections and A.I.I.s. Design flags generally apply to conflict points within the intersection rather than to segments, as discussed for the level-of-service and level-of-stress measures. Outputs related to safety or accessibility are generally higher priority items that need to be addressed in design refinements in Stage 2. Outputs related to delay and travel time and outputs related to the level of comfort are generally of lesser priority relative to safety and accessibility, suggesting items of concern but not necessarily fatal flaws in the design. Both of these levels of priority can be used to differentiate alternatives during the ICE process, and the relative balance of these levels of priority can be customized to the context of the location. Exhibit 4-5 summarizes the flags identified for pedestrians and bicyclists for various traversing, wayfinding, and crossing movements. The design flags apply to either the pedestrian movement, the bicyclist movement, or both. The flags have been derived from research including literature reviews, focus groups with users of these facilities, online surveys, expert panels, and practitioner experience. Each of the flag descriptions includes specific references to literature. The NCHRP Project 07-25 final report explains the focus group, survey, and panel input that informed the design flag development. The evaluation includes two types of design flags: • Red Flags, for design elements directly related to a safety concern for pedestrians or bicyclists, and • Yellow Flags, for design elements negatively affecting user comfort (i.e., increasing user stress) or the quality of the walking or cycling experience. The design flags are assessed for the four pedestrian crossing movements between adjacent quadrants and the 12 bicycle turning movements (left-turn, through, and right-turn for each approach). Exhibit 4-6 shows the four possible pedestrian paths part of the assessment, evaluated as two-directional movements between quadrants A, B, C, and D. Exhibit 4-7 shows the 12 bicycle turning movements feasible at most intersections. Bicycles traveling as pedestrians (e.g., walking bikes on sidewalks or children using the sidewalk net- work) should use the pedestrian assessment. U-turns are not considered in the bicycle assess- ment, because these are rare for bicyclists. Movements to or from approaches where bicyclists are prohibited (such as ramps to or from controlled-access facilities) are ignored. If a particular pedestrian path or bicycle movement is not feasible in a design, it is assumed that the corresponding pedestrian and bicycle demands are redirected to the next shortest alternate paths. Flags for that alternate path are applied to the movement under analysis. For example, if in Exhibit 4-6 pedestrian movement A-B is not allowed, those pedestrians encounter design flags for crossings B-C, C-D, and D-A.

Assessment 4-9 Sec. Design Flag Bikes Peds. Flag Type Flag Description 4.4.1 Motor Vehicle Right-Turns X Y/R Permissive motor vehicles right- turns across pedestrian paths 4.4.2 Uncomfortable/Tight Walking Environment X Y Pedestrian facilities of narrow width 4.4.3 Nonintuitive Motor Vehicle Movements X Y/R Motor vehicle movements arriving from an unexpected direction 4.4.4 Crossing Yield- or Uncontrolled Vehicle Paths X X Y/R Yield or uncontrolled pedestrian crossings 4.4.5 Indirect Paths X X Y/R Paths resulting in out-of-direction travel 4.4.6 Executing Unusual Movements X X Y Movements that are unexpected given local context 4.4.7 Multilane Crossings X X Y/R Crossing distances of significant length across multiple lanes 4.4.8 Long Red Times X X Y/R Excessive stopped delay at signalized crossings 4.4.9 Undefined Crossings at Intersections X X Y Unmarked paths through intersections 4.4.10 Motor Vehicle Left- Turns X X Y/R Permissive and protected left-turns across pedestrian and bicycle paths 4.4.11 Intersection Driveways and Side Streets X X Y/R Driveways or streets within intersection area of influence 4.4.12 Sight Distance for Gap Acceptance Movements X X R Providing adequate sight distance to conflict points 4.4.13 Grade Change X X Y/R Vertical curves adjacent to intersections 4.4.14 Riding in Mixed Traffic X Y/R On-street bicycle facilities on high- speed/volume roads 4.4.15 Bicycle Clearance Times X Y/R Bicycles require longer clearance times than vehicles at signals 4.4.16 Lane Change Across Motor Vehicle Travel Lane(s) X Y/R Lane changes by bicycles across motor vehicle lanes 4.4.17 Channelized Lanes X Y/R Bicyclist Traveling in Channelized Lane Adjacent to Motor Vehicles 4.4.18 Turning Motorists Crossing Bicycle Path X Y/R Lane changes by motor vehicles across bicycle facility 4.4.19 Riding between Travel Lanes, Lane Additions, or Lane Merges X Y/R Bicycle lanes with motor vehicle lanes on both sides 4.4.20 Off-Tracking Trucks in Multilane Curves X Y/R The tendency of trucks to swing into bicycle lanes while turning Note: Sec. = Section in this Guide; Peds. = Pedestrians; X = Applicable to this mode; Y = Yellow; R = Red Exhibit 4-5. Summary of design flags pedestrian and bicycle assessment.

4-10 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges For designs in which there is more than one way to complete a particular movement (e.g., a shared-use path adjacent to an on-street bicycle lane), the analysis should select one of these options and remain consistent over the evaluation of all flags. For each flag, one or more mitigation interventions apply and are described as part of the design techniques later in this guidebook. To assist in comparing alternatives, use the following procedure: 1. For each alternative, sum the number of yellow pedestrian flags. Repeat this step for red pedestrian flags. 2. For each alternative, divide the number of yellow pedestrian flags by the total possible number of yellow flags and multiply by 100 to determine the Percent Yellow. Repeat this step for red flags to determine the Percent Red. 3. For each alternative, sum the number of yellow bicycle flags. Repeat this step for red bicycle flags. 4. For each alternative, divide the number of yellow bicycle flags by the total possible number of yellow flags and multiply by 100 to determine the Percent Yellow. Repeat this step for red flags to determine the Percent Red. The design flag assessment presents 20 flags evaluated for pedestrians, for bicyclists, or both. For pedestrians, 13 out of the 20 flags apply, for a total of 52 potential flags (13 flags multiplied by 4 pedestrian flows). For bicycles, 17 out of the 20 flags apply, for a total of 204 potential flags (17 flags multiplied by 12 bicycle movements). An example assessment for four design alter- natives (A through D) is given in Exhibit 4-8, showing that Alternative C results in the fewest design flags for both pedestrians and bicycles. However, any alternative can be moved forward if design flags are addressed and mitigated using the guidance in Chapter 5 and the rest of this guidebook. Exhibit 4-8 summarizes all flags, including their applicability (pedestrian vs. bicyclist) and potential flag severity (yellow vs. red flag). The exhibit further contains a brief description of Exhibit 4-7. Illustration of bicycle design flag assessment. Exhibit 4-6. Illustration of pedestrian design flag assessment.

Assessment 4-11 each flag. The following sections present each design flag in detail. The provided volumes for thresholds (in vehicles per hour) refer to the peak hour. 4.4.1 Motor Vehicle Right-Turns Right-turning vehicles directly conflict with pedestrians crossing at intersections. Pedestrians often find that their path of travel is impeded by drivers inching forward to see traffic moving left to right, in preparation to making either a right-turn-on-red movement or a right-turn during a permissive green phase. With a right-turn-on-red movement, the driver sees a red signal; during a permissive right-turn, the driver sees a green ball. In both cases, the pedestrian has either a Walk or Flashing Don’t Walk indication. The driver inching forward, and even the anticipation of drivers making this movement, degrades the level of comfort for pedestrians who otherwise have a controlled crossing phase at an intersection. Motor vehicle right-turn conflicts are amplified at channelized turn lanes due to an increase in vehicle speed commonly facilitated by the larger radii of channelized turn lanes. With increasing vehicle speeds, drivers are less likely to yield to pedestrians (see Chapter 2). Channelized turn movements can also inhibit the ability of blind pedestrians to proceed into the crosswalk based on audible cues. Exhibit 4-9 illustrates the right-turn conflict for an intersection without chan- nelized lanes. Note: This flag applies only to pedestrians; turning conflicts with bicycles are evaluated in Section 4.4.18. Exhibit 4-8. Summary of design flags for pedestrian and bicycle assessment.

4-12 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges This motor vehicle right-turn design flag can be categorized as either yellow or red, depending on two dimensions: (1) vehicle right-turn speed, and (2) vehicle right-turn volume. Thresholds for these measures of effectiveness are provided in Exhibit 4-10. The vehicle right-turn speed can be estimated using the speed-radius relationship found in the AASHTO Green Book or measured in the field, while vehicle volumes are available from traffic forecasts or local counts. This flag is only applied to pedestrian paths. The “Motor Vehicle Right-Turns” flag applies to both right-turns-on-red (vehicles conflict- ing with perpendicular pedestrian crossing) and right-turns-on-green (vehicles conflicting with parallel pedestrian crossing). A special case of this flag is right-turns in channelized right-turn lanes, which may have higher vehicle speeds. Vehicle speed directly relates to pedestrian safety. Tefft found the average risk of severe injury for a pedestrian struck by a vehicle traveling 16 mph is 10%, while the risk when struck by a vehicle traveling 23 mph increases to 25% (7). Similarly, an increase in the number of vehicles turning across a pedestrian’s path increases the likelihood of the pedestrian to encounter a vehi- cle while crossing. Turning speeds less than or equal to 20 mph and vehicle volumes less than or Exhibit 4-9. Design Flag 1 – Motor vehicle right-turns. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold* Red-Flag Threshold* Motor Vehicle Right- Turns Pedestrian Vehicle Turning Speed & Vehicle Volume <=20 mph AND <= 50 veh/h >20 mph OR >50 veh/h Note: mph = miles per hour; veh/h = vehicles per hour * If the vehicle movement is stop-controlled or signalized (with no right-turns-on-red), or speeds are below 10 mph (e.g., through a raised crosswalk) this flag is eliminated. Exhibit 4-10. Design Flag 1 – Yellow- and red-flag thresholds.

Assessment 4-13 equal to 50 veh/h are therefore given a yellow flag, while a turning speed or volume beyond these thresholds increases the safety risk for the pedestrian and results in a red flag. Exhibit 4-11 shows a traditional four-legged intersection with both exclusive right-turn lanes and shared through-right lanes. At all four legs, right-turning vehicles cross marked pedestrian crosswalks. Each pedestrian movement would be identified with the appropriate flag color depending on the vehicle turning speed and volume. Given the radius of curvature, vehicle right-turn speeds are likely to be higher for the western crossing than the eastern crossing, for example. In Exhibit 4-12 an intersection with channelized turn lanes can also be flagged for motorist right-turns. Vehicle speeds at channelized turn lanes are a function of the design of the Exhibit 4-11. Design Flag 1 example. Vehicles permitted to turn right across marked crosswalks. Exhibit 4-12. Design Flag 1 example. Intersection with channelized right-turn lanes.

4-14 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Exhibit 4-14. Design Flag 2 – Yellow- and red-flag thresholds. Flag Ap p licab le M ode M easu re of E f f ectiveness Y ellow- Flag T hreshold R ed- Flag T hreshold Uncomfortable/ Tight walking environment Pedestrian Effective walkway width < 5 ft if traffic present on one side; < 1 0 ft if traffic present on two sides N/A Exhibit 4-13. Design Flag 2 – Uncomfortable/tight walking environment. channelization island (see Chapter 5). Vehicle speeds can be controlled with raised pedes- trian crossings, as shown in the top left, bottom right, and bottom left quadrants of this intersection. 4.4.2 Uncomfortable/Tight Walking Environment As most sidewalks are used for two-way pedestrian traffic, sufficient width for passing oppos- ing or slower-moving pedestrians must be provided. Pedestrians avoid walking immediately next to other modes of traffic or buildings that reduce the usable width of the sidewalk. The uncomfortable/tight walking environment flag (Exhibit 4-13) only uses the yellow flag, as shown in Exhibit 4-14. A yellow flag is warranted if less than 5 feet of width is provided for side- walks with vehicle traffic on one side. For sidewalks with traffic on two or more sides (e.g., traffic moves on three sides when pedestrians or bicyclists are positioned on a channelization island), a width of fewer than 10 feet would result in a yellow flag. This flag is only applied to pedestrian paths. Sidewalk widths are also subject to ADA requirements, which have to be considered. The flag primarily applies to pedestrians, assuming bicyclists travel on-street or on separate facilities. For multiuse path applications, the flag may also be applied to bicyclists. In these

Assessment 4-15 applications, it is important to consider any shy distance requirements from the edge of the travel lanes, or vertical obstructions. In both cases, the “effective width” is reduced by 2 feet each, recognizing that bicyclists cannot ride immediately next to these obstructions. Chapter 3 discusses bicycle dimensions and shy distances. This flag applies to walkways that travel parallel to traffic and those with traffic traveling perpendicular to traffic, or at other angles. This flag applies to walkways that travel parallel to traffic and those with traffic traveling perpendicular to the walkway, or at other angles. The flag commonly applies to walkways through channelization islands or within medians. Exhibit 4-15 shows a Z-crossing from a bus stop on the western side of the median-divided arterial to a local street on the right side. Offset barriers create a walkway through the median. The design should be evaluated for walkway width in the median; at least 10 feet is needed given traffic being present on both sides. If sidewalks were provided on the outside of the travel lanes, a 5-foot minimum walkway would be the standard for the flag evaluation of those walkways. 4.4.3 Nonintuitive Motor Vehicle Movements The nonintuitive motor vehicle movement flag is shown in Exhibit 4-16. When a pedestrian or bicyclist initiates a street crossing, the normal expectation (in countries where driving is on the right side of the roadway) is that conflicting motor vehicle traffic initially comes from the left. A common exception to this is the case of a one-way street. At some A.I.I.s, oncoming traffic may initially approach from the right. The most likely scenario where this would happen in an A.I.I. would be at a DLT where there is no right-turn bypass adjacent to the displaced left-turn movement. Also, it is common that, when two consecutive crossings are near one another, the oncoming traffic at the second crossing will be from the opposite direction of the first crossing. However, Exhibit 4-15. Design Flag 2 example. Narrow median width.

4-16 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges at channelized turn lanes and in some A.I.I. configurations, this may not always be the case. For example, in DDIs with sidewalks on the outside, oncoming traffic comes from the same direc- tion in back-to-back crossings. This can confuse a pedestrian or bicyclist, which can create a significant safety risk. Nonintuitive motor vehicle movements flags can be yellow or red, depending on the accel- eration profile of the vehicle at the conflict point. As shown in Exhibit 4-17, if the vehicle is decelerating, as is typical near the first half of a curve, a yellow flag would be assigned. If the conflict point between the pedestrian and the nonintuitive vehicle movement occurs while the vehicle is accelerating or in a free-flow condition, a red flag would be assigned. Red flags occur most frequently at interchange entrance ramps where the vehicle-pedestrian crossing is located downstream of a curve’s midpoint. This flag is only applied to pedestrian paths. At the eastern junction of the interchange in Exhibit 4-18, pedestrians traveling eastbound on the southern crosswalk at the interchange would encounter vehicles arriving from the right. The typical expectation in right-side driving countries would be to first encounter vehicles arriving from the left. At the northern crossing, it appears the crossing location is such that vehicles travel- ing east-to-north and west-to-north would both be accelerating when crossing the pedestrian path. Therefore, the northern crossing would be assigned a red flag. The southern crossing is stop-controlled and therefore no flag is assigned as the vehicle is not accelerating, decelerating, or in a free-flow condition. Exhibit 4-16. Design Flag 3 – Nonintuitive motor vehicle movements. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Nonintuitive Motor Vehicle Movements Pedestrian Vehicle acceleration profile Vehicle decelerating Vehicle accelerating or free- flowing Exhibit 4-17. Design Flag 3 – Yellow- and red-flag thresholds.

Assessment 4-17 4.4.4 Crossing Yield-Controlled or Uncontrolled Vehicle Paths The flag for crossing yield-controlled or uncontrolled vehicle paths is shown in Exhibit 4-19. Focus group discussions indicated yield-controlled and uncontrolled crossings of vehicle and pedestrian paths lead to uncomfortable and potentially unsafe interactions. Even if marked, drivers may not be looking for pedestrians at the crossing and may fail to yield to them. Such crossings are typical at channelized turn lanes found at a DLT, DDI, or RCUT. Additionally, yield-controlled or uncontrolled vehicle crossings may be present at the entrance ramp junctions of DDIs. This design flag can be categorized as either yellow or red, depending on two dimensions: (1) vehicle turn speed, and (2) vehicle turn volume. Thresholds for these measures of effec- tiveness are provided in Exhibit 4-20. The vehicle turn speed can be estimated using the Exhibit 4-18. Design Flag 3 example. Pedestrian crossing with vehicles from the right as opposed to left. Exhibit 4-19. Design Flag 4 – Crossing yield-controlled or uncontrolled vehicle paths.

4-18 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges speed-radius relationship found in the AASHTO Green Book or measured in the field, while vehicle volumes are available from traffic forecasts or local counts. This flag applies to both pedestrian and bicycle paths. The likelihood of vehicle-pedestrian or vehicle-bicycle interaction increases with an increase in vehicle volumes, while the likelihood of severe crashes increases with vehicle speed (7). Therefore, vehicle volumes greater than 50 vehicles per hour or vehicle speeds greater than 20 miles per hour indicate a red flag. Exhibit 4-21 has two yield-controlled turns, one each in the northwestern and southeastern quadrants. A visual comparison of the channelized curves suggests the southeastern radius may be larger, resulting in higher vehicle speeds. 4.4.5 Indirect Paths The indirect paths design flag is shown in Exhibit 4-22. Indirect, or out-of-direction, paths lead to a moderate level of discomfort for pedestrians and bicyclists navigating an intersection. These indirect paths are notable at traditional intersections with a closed crosswalk and at RCUT and DLT designs where circuitous pedestrian and bicyclist paths may be present. An intersection with a relatively high number of crossings for a particular origin-destination pattern not facili- tated by the design can be burdensome to pedestrians and bicyclists and detracts from the quality of service. Paths that are inefficient and burdensome may nudge pedestrians or bicyclists into risk-taking behavior in pursuit of a seemingly more convenient path not provided. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Crossing yield- controlled or uncontrolled vehicle paths Pedestrian and Bicycle Vehicle Speed & Vehicle Volume <=20 mph AND <= 50 veh/h >20 mph OR >50 veh/h Note: mph = miles per hour; veh/h = vehicles per hour Exhibit 4-20. Design Flag 4 – Yellow- and red-flag thresholds. Exhibit 4-21. Design Flag 4 example. Yield-controlled channelized turn lanes.

Assessment 4-19 The level of comfort in this assessment category is not strictly a function of the number of crossings (e.g., provision of midblock refuge to create a two-stage crossing), but rather from multiple crossings that do not lead directly to the desired destination. One such example is an intersection with the crossing of an approach leg restricted, forcing pedestrians to walk around and cross in multiple locations. The indirect paths flag can be classified as yellow or red, depending on the out-of-direction travel distance of the user (Exhibit 4-23). Thresholds are based on the delay experienced by the user, assuming a pedestrian walking speed of 3 feet per second and a bicycle speed of 15 feet per second. At a delay of 30 seconds, users are likely to execute risky behaviors to avoid further delay, while at 45 seconds, there is a high likelihood of risk-taking behavior (5). Multiplying the speed by the delay values produces the yellow and red distance thresholds. This flag can be applied to pedestrian paths or bicycle movements. Some indirect travel paths may result in additional signal delay. This occurs when the pro- vided path encounters signalized crossings that the direct path otherwise would not encoun- ter. If the signal timing does not explicitly provide progression for pedestrians and/or bicycles along the path, an additional stopped delay is likely. The indirect path flag does not account for stopped delay; it should be analyzed using the Long Red Time flag (#8). Intersections with more than four legs often result in indirect paths, as shown in Exhibit 4-24. A pedestrian traveling south along the eastern sidewalk of the northwestern leg would need to travel across the northwestern leg before continuing south, shown in blue. The desire line is shown in red. To find the total indirect length, subtract the distance of the red path from the total distance of the blue path to arrive at the portion of the path that is indirect. Exhibit 4-25 shows a four-leg intersection in which one leg is not marked for crossing. The intended path of a pedestrian arriving at the northwest quadrant and desiring to travel to the southwest quadrant is to first travel east, then south, then return west. To find the indirect path distance, the distance to cross directly from the northwest quadrant to the southwest quadrant should be subtracted from the distance to travel east, then south, then west. Exhibit 4-22. Design Flag 5 – Indirect paths. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Indirect Paths Pedestrian & Bicycle Out-of-direction travel distance 90 ft (ped) 450 ft (bike) 135 ft (ped) 675 ft (bike) Note: ft = feet Exhibit 4-23. Design Flag 5 – Yellow- and red-flag thresholds.

4-20 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Exhibit 4-24. Design Flag 5 example. Out-of- direction travel for southbound crossing. Exhibit 4-25 Design Flag 5 example. Out-of- direction travel for southbound crossing.

Assessment 4-21 4.4.6 Executing Unusual Movements The executing unusual movements design flag is shown in Exhibit 4-26. Design consistency helps roadway users by setting expectations for how to move around a network and through an intersection. Just as drivers have expectations for various movements at an intersection, pedestrians and bicyclists have similar expectations about typical crossing patterns at inter- sections. This flag captures the confusion users may experience upon arriving at an intersection and being unsure of how to continue on the desired path. This flag is most commonly seen at DDIs with inside paths, RCUTs with Z-crossing designs, and DLTs with channelized turns and multiple crossing stages. The first two are examples of paths that may require users to travel along an indirect path. [Note: depending on the distance of indirect travel, an indirect path flag (flag #5) may also be assigned]. The DLT with channelized turns and multiple crossing stages may be unusual due to the significant number of stages needed to cross a single leg of the intersection. Users may not expect to encounter multiple islands and refuge areas. This design flag can only be yellow and is based on local expectations as shown in Exhibit 4-27. The general familiarity of movement by the public may best be gathered through public meetings and a thorough understanding of local practices. The first-of-its-kind design in an area may be flagged for an unusual movement, but if, over time, the design is replicated, the movement may no longer be unusual to the user. This flag is not intended to be used for expected, or common, movements that are unpopular or undesirable by the public. Typically, the lack of desirability would indicate another flag might be present (e.g., indirect path, motor vehicle right-turns, riding in mixed traffic, etc.). This flag can be applied to pedestrian paths or bicycle movements. In Exhibit 4-28, the southwest/northeast street is a one-way, two-lane road that transitions to a one-way, one-lane road southwest of the intersection. A southwest bound bicycle origi- nating in a shared bicycle-motor vehicle lane is presented with a marked bike lane to the left that Exhibit 4-26. Design Flag 6 – Executing unusual movements. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Executing Unusual Movements Pedestrian & Bicycle Local Expectation The path does not match the expectation N/A Exhibit 4-27. Design Flag 6 – Yellow- and red-flag thresholds.

4-22 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges proceeds across the intersection into a two-way cycle track. In most locations, the presentation of an exclusive bicycle lane developing between two vehicular lanes and proceeding at an angle through an intersection would be considered an unusual movement. 4.4.7 Multilane Crossings The multilane crossings design flag is shown in Exhibit 4-29. Long crossings, particularly with multiple lanes from both directions, are a source of stress and potentially risk at intersections. Pedestrians in focus groups noted a comfort-based preference for shorter crossings with median Exhibit 4-28. Design Flag 6 example. Bike lane developing between lanes. Exhibit 4-29. Design Flag 7 – Unassisted multilane crossings.

Assessment 4-23 refuges, for crossing one direction of travel at a time, and for having raised separation between opposing directions of traffic. Similar considerations apply for bicyclists. This flag can be classified as either yellow or red, depending on the number of vehicle travel lanes crossed without refuge as shown in Exhibit 4-30. This flag can be applied to pedestrian paths or bicycle movements. The number of lanes is irrespective of the direction of travel. Bicycle lanes and parking lanes are not counted in this assessment. For example, the following would all be classified as a yellow flag: • A pedestrian crossing three lanes of traffic in the same direction • A pedestrian crossing two lanes of traffic in one direction and one lane of traffic in the oppos- ing direction • A pedestrian crossing two or more lanes of opposing traffic plus a two-way-left-turn-lane. Pedestrian paths along each of the four legs in Exhibit 4-31 would qualify for a yellow flag. The eastern, southern, and western paths all cross three vehicle travel lanes while the northern path crosses two lanes. Bicycle lanes and parking lanes do not count toward the flag threshold. For bicycles, no movement crosses four vehicle lanes, so there would be no bicycle flags for this intersection. 4.4.8 Long Red Times The long red times design flag is shown in Exhibit 4-32. Both pedestrians and bicyclists can experience extended delays due to long cycle lengths and the number of phases over which Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Multilane crossing Pedestrian & Bicycle Number of lanes without refuge 2 – 3 lanes (ped) 4 – 5 lanes (bike) >3 lanes (ped) >5 lanes (bike) Exhibit 4-30. Design Flag 7 – Yellow- and red-flag thresholds. Exhibit 4-31. Design Flag 7 example. Pedestrian and bicycle crossings conflicting with 2 and 3 vehicle lanes.

4-24 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges a particular origin-destination movement must be completed. These delays should be minimized to the extent possible. Excessive delays can result in reduced compliance through an increase in risk-taking behavior. Crossings which must be completed in multiple stages, or over multiple phases or multiple cycles (such as through a bicycle box to execute a left-turn or a pedestrian needing to cross two legs of an intersection to execute a diagonal route) commonly result in long delays due to the cumulative effect of the red times. This flag can be classified as either yellow or red, depending on stopped delay (Exhibit 4-33). At a delay of 30 seconds, users are likely to execute risky behaviors to avoid further delay, while at 45 seconds, there is a high likelihood (4). This flag can be applied to pedestrian paths or bicycle movements. For pedestrians, the flag is assessed for each quadrant-to-quadrant cross- ing. If a connection is not provided, the resulting delay is cumulative across the shortest feasible route. For multistage crossings, the delay is also evaluated across all stages of the crossing. For bikes, the delay is assessed for each turning movement. For bicycle movements that are redirected (e.g., through a MUT or RCUT U-turn) the total cumulative delay is considered. If a bicycle movement requires the use of two phases, such as with a bicycle box to execute a left-turn, the total delay experienced over both phases should be considered. However, engineer- ing judgment should be used to determine how the phase order would affect the delay experi- enced for the second phase. Out-of-direction travel time is not considered in the delay measure, because it is separately accounted for in flag #5. Exhibit 4-33. Design Flag 8 – Yellow- and red-flag thresholds. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Long Red Times Pedestrian & Bicycle Delay 30 seconds 45 seconds Exhibit 4-32. Design Flag 8 – Long red times.

Assessment 4-25 A planning-level estimation of delay can be made using the equation below. This method assumes random arrival at the intersection. Therefore, the delay calculation may not be appro- priate for movements that require multiple phases (e.g., the second phase of a bicycle box- enabled left-turn movement): 2 2 =Delay r C Where: r = movement red time (seconds) C = cycle length (seconds) When the movement red time is not known, the estimates in Exhibit 4-34 can be used to find the percent of the time a movement is red relative to the cycle length. This percent should be multi- plied by the cycle length to determine the value of red time in seconds. Movements that proceed with the major vehicle movement (e.g., major street through) typically have less red time than movements that proceed with minor vehicle movements (e.g., cross street through, left-turns) A pedestrian crossing eastbound or westbound with the minor street in Exhibit 4-35 may experience long red times. Minor streets typically have shorter green times relative to major streets, and exclusive left-turn lanes on each leg indicate the possibility of protected or protected- permissive left-turn phases, which increases the cycle length. # Critical Phases % Red Time of Cycle Length Crossing with Major Vehicle Movement Crossing with Minor Vehicle Movement 2 30% 70% 3 50% 75% 4 60% 85% Exhibit 4-34. Percent red time reference table. Exhibit 4-35. Design Flag 8 example. Large intersection with possible long red times.

4-26 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 4.4.9 Undefined Crossings at Intersections The undefined crossings at intersections design flag is shown in Exhibit 4-36. For all inter- section forms, unmarked or undesignated space at an intersection can lower the level of comfort when walking or biking. Absent clear pavement demarcation, right-turning drivers are more likely to encroach on pedestrian and bicyclist crossings, creating conflicts. Additionally, right- turning or left-turning vehicles may not expect pedestrians or bicycles at the downstream crossing point. For example, in Exhibit 4-36, westbound-to-northbound right-turning vehicles may not expect pedestrians and bicycles to be traveling along the northern leg despite those users likely having the right-of-way. This flag can be classified only as a yellow flag as shown in Exhibit 4-37. If there is no marking through the intersection for the movement, the yellow flag should be applied. This includes bicycle lane markings that are present on both sides of the intersection but do not extend through the intersection. This flag can be applied to pedestrian paths or bicycle movements. Right-turn and left-turn bicycle movements are exempt from this flag. Exhibit 4-38 shows a situation with pedestrian crossings along all four legs; this situation would not receive a flag for any of the pedestrian path evaluations. However, the eastbound through and westbound through bicycle movements have exclusive lanes for which markings do not extend through the intersection. Therefore, the eastbound through and westbound through movements would receive a yellow flag. Because the northbound and southbound through movements do not have exclusive bicycle lanes nor a shared-use path, this flag does not apply. Exhibit 4-36. Design Flag 9 – Undefined crossings at intersections. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Undefined Crossings at Intersections Pedestrian & Bicycle Path Markings Unmarked crossing N/A Exhibit 4-37. Design Flag 9 – Yellow-flag thresholds.

Assessment 4-27 Exhibit 4-38. Design Flag 9 example. Westbound bicycle lane without markings in the intersection. Exhibit 4-39. Design Flag 9 example. Undefined vehicle right-turn space. In Exhibit 4-39, crosswalks exist at all legs and from the curb through a channelized vehicle right-turn. However, the resulting large undefined space adjacent to the vehicle right-turns has no clear pedestrian demarcation and does not use a raised channelization island. This results in a yellow flag for pedestrians crossing through that space. 4.4.10 Motor Vehicle Left-Turns The motor vehicle left-turns design flag is shown in Exhibit 4-40. Both permissive and pro- tected motor vehicle left-turns can affect the safety and comfort of pedestrians and bicyclists. While pedestrians are crossing or bicyclists are making a through movement, permissive left- turning drivers are often focused on finding a gap in oncoming motor vehicle traffic and may not be watching out for nonmotorized road users. Similarly, one study found that leading protected left-turns lead to more pedestrian-vehicle conflicts (8). This may be because, on seeing a red indication on the opposing street, the pedestrian expectation may be to receive a walk indication. Pedestrians may not realize the conflicting leading protected left-turn has been given the green indication but the walk interval has not yet started.

4-28 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges This design flag can be categorized as either yellow or red, depending on two dimensions: (1) vehicle turn speed, and (2) vehicle turn volume. Thresholds for these measures of effective- ness are provided in Exhibit 4-41. The vehicle turn speed can be estimated using the speed-radius relationship found in the AASHTO Green Book or measured in the field, while vehicle volumes are available from traffic forecasts or local counts. This flag can be applied to pedestrian paths or bicycle movements. Exhibit 4-42 shows the conflict between a heavy pedestrian movement and a left-turning vehicle. Although the vehicle is turning from a one-way road and, therefore, the driver need not look for gaps in oncoming vehicles, the heavy pedestrian volume may reduce the capacity of the Exhibit 4-40. Design Flag 10 – Motor vehicle left-turns. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Motor Vehicle Left-Turns Pedestrian & Bicycle Vehicle Turning Speed & Vehicle Volume <=20 mph AND <= 50 veh/h >20 mph OR >50 veh/h Note: mph = miles per hour; veh/h = vehicles per hour Exhibit 4-41. Design Flag 10 – Yellow- and red-flag thresholds. Exhibit 4-42. Design Flag 10 example. Conflict between left-turning vehicle and pedestrians.

Assessment 4-29 left-turning movement and thus increase vehicle delay and the likelihood of a driver accepting an inappropriately small gap in the pedestrian flow. Exhibit 4-43 shows a more traditional permissive left-turn conflict with two-directional traffic. Once a left-turning driver sees a gap in the oncoming vehicles, he or she will accelerate to com- plete the left-turn movement and may not see the pedestrian or cyclist until either it is too late to stop or he or she is forced to stop in the path of conflicting motor vehicles. 4.4.11 Intersecting Driveways and Side Streets The intersecting driveways and side streets design flag is shown in Exhibit 4-44. Driveways and sidestreets near intersections can result in an increased cognitive load and distractions for all users. Users at the intersection and the driveway and sidestreet may be focused on monitoring multiple traffic streams for noncompliant behavior at the expense of monitoring the users in the immediate vicinity. Driveways and side streets that intersect with two-way bicycle lanes or cycle tracks (either at street or sidewalk level) are of particular concern. Drivers attempting to turn right out of a driveway or sidestreet and merge with traffic traveling left to right may not expect or look for bicycles traveling right to left (because the driver’s attention is to their left to screen for gaps in vehicular traffic). This flag can be classified as either yellow or red depending on three factors as shown in Exhibit 4-45: (1) the mode of travel, (2) the number of directions of travel, and (3) the number of driveways or side streets in the area of influence. The area of influence is the greater of 250 feet in both directions from the center of the main intersection (for a total of 500 feet) or the entire frontage area along the path through the intersection. For example, a DLT with a median pedes- trian walkway that extends 800 feet from the main intersection before returning pedestrians to the outside sidewalk would have an area of influence of 800 feet for that path. This flag can be applied to pedestrian paths or bicycle movements. Given the increased concern of vehicle/bicycle interaction at two-way bicycle facilities, any access points present within the area of influence should be classified as a red flag. For pedestrian facilities and one-way bicycle facilities, one or two access points should be classified as a yellow flag, while more than two should be classified as a red flag. Exhibit 4-43. Design Flag 10 example. Permissive left-turns.

4-30 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Exhibit 4-44. Design Flag 11 – Intersecting driveways and side streets. Flag Applicable Mode Measure of Effectiveness Yellow- Flag Threshold Red-Flag Threshold Intersecting Driveways and Side Streets Pedestrian & Bicycle # of Access points in Area of Influence 1-2 (peds) 1-2 (one- way bikes) >2 (peds) >2 (one- way bikes) >0 (two- way bikes) Exhibit 4-45. Design Flag 11 – Yellow- and red-flag thresholds. In Exhibit 4-46, bicycles traveling northbound and pedestrians traveling north- or south- bound on the eastern side of the intersection encounter four driveways (shown as red Xs) within the 500-foot total area of influence shown. This would classify as a red flag for those paths and movements. A right-turning east to north bicycle encounters five access points classifying the movement as a red flag. Exhibit 4-47 shows a two-way multiuse path on the east side of the intersection resulting in potential conflicts with right- and left-turning vehicles – particularly for pedestrians and bicycles approaching from the north (given that drivers tend to look south for gaps).

Assessment 4-31 Exhibit 4-46. Design Flag 11 example. Significant number of driveways and side streets adjacent to the intersection. Exhibit 4-47. Design Flag 11 example. Multiuse path crossing.

4-32 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 4.4.12 Sight Distance for Gap Acceptance Movements The design flag describing sight distance for gap acceptance movements is shown in Exhibit 4-48. Throughout the design, sight distance must be provided. Sight distance includes these components: • Stopping sight distance: the distance for drivers to react to objects in the roadway, including pedestrians and bicyclists in conflict areas. • Intersection sight distance: the distance for drivers to see oncoming drivers and bicycles and pedestrians, and vice versa. The concept of pedestrian crossing sight distance was introduced in NCHRP Report 834 (9) and should be provided to ensure that pedestrians can see far enough to judge gaps necessary for crossing adequately. • Decision sight distance: the distance when in motion for drivers to make decisions, such as lane selection. • View angles: when looking to the left or right, a driver’s view angle should not exceed 15 degrees beyond a line perpendicular to the alignment of the vehicle. Oncoming vehicles, bicyclists, and pedestrians located beyond this angle may be in a driver’s blind spot and thus not visible. This flag should be classified as red if the required sight distance is not provided, as shown in Exhibit 4-49. Sight distance requirements by vehicle speeds can be found in the AASHTO Green Book and NCHRP Report 834 for pedestrians. This flag can be applied to pedestrian paths or bicycle movements. Exhibit 4-50 and Exhibit 4-51 show the plan and profile images of a T-intersection. Due to vertical and horizontal curves, a vehicle traveling south along the mainline may not have Design Flag: Vertical or horizontal alignments, or roadside elements (e.g., bridge abutment, fencing) may impede sight distance at yield- controlled movements. Exhibit 4-48. Design Flag 12 – Sight distance for gap acceptance movements.

Assessment 4-33 Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Sight distance for gap acceptance movements Pedestrian & Bicycle Sight Distance N/A Less than required for vehicle speed Exhibit 4-49. Design Flag 12 – Red-flag thresholds. Exhibit 4-51. Design Flag 12 example. Profile view of the intersection with significant vertical and horizontal curves limiting sight distance. Exhibit 4-50. Design Flag 12 example. Plan view of the intersection with significant vertical and horizontal curves limiting sight distance.

4-34 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges appropriate sight distance for pedestrians standing on the northeast quadrant preparing to cross the mainline to the west. 4.4.13 Grade Change The grade change design flag is shown in Exhibit 4-52. Grade changes within or immediately next to an intersection can create challenges for pedestrians and bicycles. For bicycles, positive grades require more power to increase or maintain speeds. If a bicycle is stopped, such as at a red signal indication or while yielding at a permissive movement, initiating movement uphill without lateral deviation in the path can be especially challenging. Pedestrians, particularly those with mobility challenges or those carrying or pushing other objects (e.g., strollers and groceries) can face problems with both positive and negative grades. On an uphill, pedestrians may move more slowly, thus increasing the time necessary to clear the intersection. On a downhill, pedes- trians with lower joint problems may slow down to reduce the impact on ankle, knee, and hip joints. Pedestrians using or pushing objects with wheels may struggle to maintain control as gravity’s effect increases the travel speed. This flag can be classified as either yellow or red, depending on the steepest grade experienced along the path or movement. The thresholds are shown in Exhibit 4-53. Grades with a positive or negative slope of 3 to 5 degrees would be classified as a yellow flag, while grades with a positive or negative slope exceeding 5 degrees would be classified as a red flag. The slope of curb ramps should not be considered in determining the steepest grade but should still conform to ADA requirements. This flag can be applied to pedestrian paths or bicycle movements. Exhibit 4-54 shows a steep uphill grade headed northbound immediately next to the inter- section. Northbound bicyclists who must stop for a red indication have only the width of the intersection to gain speed before beginning the descent. Those traveling eastbound may need to slow or stop completely to yield to oncoming traffic. Vehicles traveling down an incline may be less likely to yield to pedestrians. Exhibit 4-52. Design Flag 13 – Grade change. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Grade Change Pedestrian & Bicycle % grade +3% to +5% OR -3% to -5% <–5% OR >+5% Exhibit 4-53. Design Flag 13 – Yellow- and red-flag thresholds.

Assessment 4-35 4.4.14 Riding in Mixed Traffic The riding in mixed traffic design flag is illustrated in Exhibit 4-55. As noted in Chapter 3, riding in mixed traffic next to motorized vehicles with high speeds, high volumes, or both have been documented as both a safety issue and a comfort issue for bicyclists. A heavy volume of motor vehicles or vehicles traveling at a higher speed can create a high level of stress for bicyclists and an increased likelihood of severe injury or death if a bicyclist-motorist collision occurs. This flag can be classified as yellow or red, depending on two dimensions: (1) vehicle speed and (2) vehicle volume per day as shown in Exhibit 4-56. Thresholds are based on FHWA’s Bike- way Selection Guide (10) and were shown in Chapter 3 of this guidebook. The yellow threshold corresponds to the recommended conditions for use of an on-street bike lane, preferably with a buffer, while the red threshold corresponds to the recommended conditions for a separated bike lane or shared-use path. Shared-lane designs are subject to both the yellow and red thresholds, while bike lanes are subject only to the red threshold. Vehicle speed can be determined by field data collection or, absent such data, by using the design speed. Engineering judgment should be applied to determine if the expected vehicle speed might be higher or lower than the design speed, given the intersection environment. Vehicle volume can be found from traffic forecasts or local counts. This flag can only be applied to bicycle movements. Exhibit 4-54. Design Flag 13 example. Significant uphill grade adjacent to intersection. Exhibit 4-55. Design Flag 14 – Riding in mixed traffic.

4-36 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Exhibit 4-57 shows an intersection with a posted 25 mph speed limit on the east-west street and a 35 mph speed limit on the north-south street. On both streets, there is a dedicated bike lane with no buffer. Because the design uses a bike lane, only the red threshold should be evaluated. Both roadways are at or under the 35 mph posted speed, although local data may reveal actual vehicle speeds to be higher than 35 mph. If so, the red flag would be applied. If actual vehicle speeds are at or under 35 mph, the total daily vehicle volume on each road should be analyzed. 4.4.15 Bicycle Clearance Time The bicycle clearance time design flag is illustrated in Exhibit 4-58. Clearance time is deter- mined specifically for motorists and pedestrians in the calculations of yellow and red intervals for motorists and flashing Don’t Walk time for pedestrians. Neither clearance time calculation is likely appropriate for bicycles, given their travel speed relative to pedestrians or motor vehicles. Bicyclists using signals for motor vehicles must use personal judgment to determine if there is enough time to clear the intersection. Absent bicycle-specific signals, there are typically two options to assist bicyclists in this decision: • If a pedestrian signal is present with a countdown indicator, bicyclists may get a better idea of when the signal indication is about to change. It is still up to the bicyclists to determine how much time they need to cross and to decide whether to attempt a crossing. The decision to Exhibit 4-57. Design Flag 14 example. On-street bicycle lanes adjacent to heavy volume roadway. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Riding in Mixed Traffic Bicycle Vehicle Speed & Vehicle Volume 25-35 mph OR 3,000 – 7,000 vpd >35 mph OR >7,000 vpd Note: mph = miles per hour; vpd = vehicles per day Exhibit 4-56. Design Flag 14 – Yellow- and red-flag thresholds.

Assessment 4-37 cross may occasionally lead to a bicyclist being in the intersection when a conflicting move- ment receives a green indication. • At many signals, a cyclist can only rely on the yellow indications for motorists. This yellow clearance interval is designed for motorists and is generally 3 to 6 seconds, per the MUTCD (11). This clearance time is rarely enough time for cyclists to clear the intersection. The problem worsens with larger speed differentials between motorists and bicyclists, as well as with larger intersections. In A.I.I.s, clearance time can often become a bigger issue for cyclists with multiple medians (DLT), wide medians (RCUT, MUT), and gaps between movements (DDI). The issue is com- pounded in most DDIs and some DLTs when signal heads are placed before the full clearance of the intersection. In those situations, bicyclists have no indication if the signal phase has changed once they have ridden past the signal heads. This flag can be classified as either yellow or red and is a function of the length of the roadway section over which clearance times are calculated, as shown in Exhibit 4-59. The average bicycle travel speed is approximately 10 to 14 mph. Compared to a vehicle traveling at 35 to 50 mph, Exhibit 4-58. Design Flag 15 – Bicycle clearance time. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Bicycle Clearance Times Bicycle Vehicle Speed and Clearance Zone Length (feet) <=35 mph and 36–72 ft OR > 35 mph and 24–60 ft <=35 mph and >=72 ft OR > 35 mph and >=60 ft Note: mph = miles per hour; ft = feet Exhibit 4-59. Design Flag 15 – Yellow- and red-flag thresholds.

4-38 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges a bicycle, therefore, requires 3 to 5 times the clearance times calculated for motorized traffic. This flag can only be applied to bicycle movements. The thresholds in Exhibit 4-59 assume a bicycle travel speed of 12 mph. Exhibit 4-60 shows a north-south on-street bike lane crossing a four-lane urban arterial. At a sidestreet travel speed of 35 mph, this 48-foot crossing distance is classified as a yellow flag. At 35 mph, the estimated vehicle clearance time (resulting in the calculated all-red time) is 0.9 seconds, compared to 2.7 seconds required for a bicycle to clear the arterial. The resulting difference of 1.8 seconds is equal to the potential time a bicyclist may still be within the inter- section after the vehicle mainline has gotten a green signal indication. Given a typical vehicle start-up lost time of 2 seconds, this is classified as a yellow flag. However, had the intersection been wider, the added exposure in the roadway after east-west vehicular green would have resulted in a red flag. 4.4.16 Lane Change Across Motor Vehicle Travel Lane(s) The design flag for lane change across motor vehicle travel lane(s) is shown in Exhibit 4-61. For bicyclists, movements that require lane changes over motor vehicle travel lanes, while bicyclists are moving with traffic, are both a safety and comfort concern. To complete this maneuver, bicy- clists have to look over their shoulders to assess gaps available for lane changes while riding. At high vehicle speeds and volumes, this maneuver can be stressful and even dangerous to complete, as bicyclists have to maintain their trajectory while scanning for gaps. Specific examples noted in focus group research include the following: • Approaching the U-turn movement at an MUT or RCUT; • Approaching the displaced left-turn movement at a DLT; and • Approaching a left-turn lane at most traditional intersections. Perpendicular crossings of motor vehicle lanes (from a stopped bicycle position) should be evaluated using design flag #4. Exhibit 4-60. Design Flag 15 example. Bicycle clearance time.

Assessment 4-39 Exhibit 4-62. Design Flag 16 – Yellow- and red-flag thresholds. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Lane change across the motor vehicle travel lane Bicycle Vehicle Speed & Vehicle Volume 25–35 mph OR 3,000–7,000 vpd >35 mph OR >7,000 vpd Note: mph = miles per hour; vpd = vehicles per day Exhibit 4-61. Design Flag 16 – Lane change across motor vehicle travel lane(s). Exhibit 4-63. Design Flag 16 example. Southbound bicycle path departing bike lane and crossing vehicle lane to turn left downstream.

4-40 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Exhibit 4-64. Design Flag 17 – Bicyclists traveling in channelized lane adjacent to motor vehicles. This flag can be classified as yellow or red, depending on two dimensions: (1) vehicle speed and (2) vehicle volume per day as shown in Exhibit 4-62. Thresholds are based on FHWA’s Bikeway Selection Guide (10). Any uncontrolled movement requiring a bicycle to cross a motor vehicle travel lane, regardless of the bicycle facility type, is subject to both the yellow and red thresholds. Vehicle speed can be determined by field data collection or, absent such data, by using the design speed. Engineering judgment should be applied to determine if the expected vehicle speed might be higher or lower than the design speed, given the intersection environment. Vehicle volume can be found from traffic forecasts or local counts. This flag can only be applied to bicycle movements. Exhibit 4-63 shows a southbound bicycle lane crossing a T-intersection and proceeding downstream to a larger intersection with left- and right-turn bays. Bicycles traveling southbound desiring to make a left-turn at the downstream intersection must cross the southbound vehicle lane to move into the left-turn bay. The actual vehicle travel speed and the daily roadway volume would be needed to determine which flag, if either, applies to this design. 4.4.17 Channelized Lanes The channelized lanes design flag is illustrated in Exhibit 4-64. For bicyclists, situations where bicyclists travel in a channelized lane with motorized traffic are both a safety and a comfort concern. The flag applies to single-lane channelized lanes (narrow shared space between curbs) and multilane facilities. The latter situation may also be covered by design flag #19 and should not be double-counted. Specific examples noted in focus group research include the following: • Traversing a channelized left-turn lane at a DLT; and • Traversing a channelized right-turn bypass lane. This flag can be classified as yellow or red depending on two dimensions: (1) vehicle speed and (2) length of the channelized lane (see Exhibit 4-65). The speed thresholds are based on FHWA’s Bikeway Selection Guide (10), while the length thresholds are based on the exposure time of 3 seconds at an assumed bicycle travel speed of 12 mph (17.6 ft/s). The yellow and red flags are applicable regardless of the bicycle facility type. Vehicle speed can be determined by field data collection or, absent such data, by using the design speed. Engineering judgment should be applied to determine if the expected vehicle

Assessment 4-41 speed might be higher or lower than the design speed given the intersection environment. The channelization length should be measured from the design concepts, aerial surveys, or field measurements. This flag can only be applied to bicycle movements. In Exhibit 4-66, the single-lane roundabout features channelized lanes, which can be a chal- lenging riding environment. This is especially true in the eastbound direction, where a significant upgrade results in slow-moving cyclists. Here, the agency widened the sidewalk to a multiuse path to allow cyclists to use it as a “bypass lane” and avoid the channelized section. For the south- bound right-turns, channelization remains a potential design flag, creating an uncomfortable riding environment for cyclists. The right-turn channelization exceeds a length of 50 feet and would be classified as a red flag per Exhibit 4-65. For the eastbound through movement, no flag is applied because bicyclists can use the bypass option on the multiuse path section. 4.4.18 Turning Motorists Crossing Bicycle Path The design flag for turning motorists crossing bicycle path is shown in Exhibit 4-67. For bicyclists proceeding straight through an intersection, the conflict zone where motor vehicle traffic can cross the bike path of travel creates a safety concern and source of user stress. This situation commonly applies to right-turning traffic at most intersections. This conflict is also called the “right hook” conflict. A right hook occurs when a vehicle passes a (slower) bicycle in the approach to an intersection. As the vehicle slows down to make right- turns at the intersection, the bicyclist can catch up with the vehicle. As the vehicle turns, the driver may not be aware of the cyclist (in their blind spot), creating a conflict and potential crash. This flag can only be applied to bicycle movements, as shown in Exhibit 4-68. It can be classi- fied as either yellow or red, depending on the facility. For an exclusive turn lane or channelized Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Channelized Lanes Bicycle Vehicle Speed & Channelization Length 25-35 mph AND <= 50 ft >35 mph OR >50 ft Note: mph = miles per hour; ft = feet Exhibit 4-65. Design Flag 17 – Yellow- and red-flag thresholds. Exhibit 4-66. Design Flag 17 example. Bicycle exposure in channelized turns.

4-42 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Exhibit 4-67. Design Flag 18 – Turning motorists crossing bicycle path. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Turning motor vehicles crossing the bike path Bicycle Motor Vehicle Lane Configuration Exclusive Turn Lane Shared Thru & Turn Lane Exhibit 4-68. Design Flag 18 – Yellow- and red-flag thresholds. lane, the vehicle lane change happens at a higher speed relative to the cyclist, resulting in a yellow flag. For a shared through and right lane, the “right hook” situation described above is more likely to surprise the driver, resulting in a red flag. In Exhibit 4-69, the eastbound and westbound approaches are classified as yellow flags, because the vehicle right-turn has a dedicated lane in each case. For the northbound and south- bound approaches, shared through-right lanes would result in a red flag, but no flag applies in this case because traffic is controlled by a stop sign (however, flag #1 may apply). In Exhibit 4-70, the bike lanes in the eastbound and westbound directions are next to through- right shared lanes and are therefore considered red flags. 4.4.19 Riding Between Travel Lanes, Lane Additions, or Lane Merges The design flag for riding between travel lanes, lane additions, or lane merges is shown in Exhibit 4-71. Bicyclists often travel between vehicular travel lanes, with traffic on both sides of the cyclist. There are two common occurrences of this flag: • Upstream of intersections, with a bike lane between the vehicular right-turn-lane and through lane(s); and • Downstream of intersections, with a bike lane between a vehicle merge or acceleration lane and the through lane(s).

Assessment 4-43 Exhibit 4-69. Design Flag 18 example. Right-turning vehicles crossing bicycle lane with an exclusive right-turn lane. Exhibit 4-70. Design Flag 18 example. Right-turning vehicles crossing bicycle lane with shared through- right-lane. Exhibit 4-71. Design Flag 19 – Riding between travel lanes, lane additions, or lane merges.

4-44 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Typically, the downstream situation is more severe because merging traffic has to switch lanes across the bike path (see flag #18), but both situations can be of concern for cyclists. This flag can be classified as yellow or red, depending on the maneuver, as shown in Exhibit 4-72. If motor vehicle lanes remain parallel to the bike movement or diverge, the flag is generally categorized as yellow. If motor vehicle lanes merge, forcing a lane change across the bicycle path, the flag is categorized as red. This flag can only be applied to bicycle movements and should not be double-counted with flag #18. Exhibit 4-73 shows a westbound bike lane that ends between a vehicular through lane and a right-hand merge lane. This situation would be classified as a red flag, especially given the likely high vehicle speeds on the merge lane. The flag exists even if there is not a bike lane. In Exhibit 4-74, the eastbound bike lane drops before a merge situation, but cyclists will still find themselves between two travel lanes with the right lane merging across, resulting in a red flag. 4.4.20 Off-Tracking Trucks in Multilane Curves The off-tracking trucks in multilane curves design flag is shown in Exhibit 4-75. Focus group interviews with cyclists have revealed a comfort and safety concern when traveling through curved roadways alongside traffic, especially trucks. Depending on curvature and lane widths, heavy vehicles may off-track into adjacent lanes, resulting in a comfort and safety concern for cyclists. Specific examples noted in focus group research include the following: • Traversing a crossover at a DDI, • Traversing a multilane crossover at a DLT, and • Traversing a multilane U-turn maneuver at an RCUT or MUT. Exhibit 4-72. Design Flag 19 – Yellow- and red-flag thresholds. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Riding between Travel Lanes, Lane Additions, or Lane Merges Bicycle Motor Vehicle Lane configuration Motor vehicle lanes remain parallel or diverge Motor vehicle lanes merge Exhibit 4-73. Design Flag 19 example. Westbound bicycle lane between merging motor vehicle lanes.

Assessment 4-45 Exhibit 4-74. Design Flag 19 example. Eastbound bicycle lane drops as the motor vehicle lane is added on the right. Exhibit 4-75. Design Flag 20 – Off-tracking trucks in multilane curves. This flag can be classified as yellow or red, depending on the angle of the curve to be tra- versed, as shown in Exhibit 4-76. For turns at 60 degrees or less, the flag is categorized as a yellow-flag, with higher angle turns resulting in a red flag. This flag can only be applied to bicycle movements. Besides A.I.I.s, this flag can apply to multilane turns at traditional intersections and multilane roundabouts. Another example is shown in Exhibit 4-77, where the back-to-back and reverse curvature on entering the rotary intersection can result in challenges for bikes. Given the total curvature exceeding 60 degrees, this situation would be classified as a red flag. Flag Applicable Mode Measure of Effectiveness Yellow-Flag Threshold Red-Flag Threshold Off-Tracking Trucks in Multilane Curves Bicycle Turn Angle Curve at 60 degrees or less Curve at greater than 60 degrees Exhibit 4-76. Design Flag 20 – Yellow- and red-flag thresholds.

4-46 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges 4.5 Design Flag Assessment Scoring Sheets Exhibit 4-78 and Exhibit 4-79 can be used as scoring sheets. A new sheet should be used for each design alternative. Column labels can be modified to reflect the paths (for pedestrians) or movements (for bicycles) necessary for the design. Exhibit 4-77. Design Flag 20 – Example application at rotary traffic circle.

Assessment 4-47 Pedestrian Flags NCHRP 7-25 Method Date: Project: Alternative: Intersection/Interchange: Analyst: No. Name West East North South 1 Motor Vehicle Right-Turn 2 Uncomfortable/ Tight Walking Environment 3 Nonintuitive Motor Vehicle Movement 4 Crossing Yield or Uncontrolled Vehicle Paths 5 Indirect Paths 6 Executing Unusual Movements 7 Multilane Crossing 8 Long Red Times 9 Undefined Crossing at Intersections 10 Motor Vehicle Left-Turn 11 Intersecting Driveways and Side Streets 12 Sight Distance for Gap Acceptance 13 Grade Change Total Possible Flags Total Yellow Flags Total Red Flags PCT Yellow PCT Red PCT Flagged Indicate R=red flag, Y=yellow flag, or blank=no flag Study Area Sketch with Path Assignment Exhibit 4-78. Pedestrian Design Flag assessment scoring sheet.

4-48 Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges Bicycle Flags NCHRP 07-25 Method Date: Project: Alternative: Intersection/Interchange: Analyst: No. Name N BL N BT N BR SB L SB T SB R EB L EB T EB R W BL W BT W BR 4 Crossing Yield or Uncontrolled Vehicle Paths 5 Indirect Paths 6 Executing Unusual Movements 7 Multilane Crossing 8 Long Red Times 9 Undefined Crossing at Intersections 10 Motor Vehicle Left-Turn 11 Intersecting Driveways and Side Streets 12 Sight Distance for Gap Acceptance 13 Grade Change 14 Riding in Mixed Traffic 15 Bicycle Clearance Times 16 Lane Change Across Motor Vehicle Lanes 17 Channelized Lanes 18 Turning Motorists Crossing Bicycle Path 19 Riding Between Travel Lanes 20 Off-Tracking Trucks in Multilane Curves Total Possible Flags Total Yellow Flags Total Red Flags PCT Yellow PCT Red PCT Flagged Indicate R=red flag, Y=yellow flag, or blank=no flag Study Area Sketch with Route Assignment Exhibit 4-79. Bicycle Design Flag assessment scoring sheet.

Assessment 4-49 4.6 References 1. FHWA. Capacity Analysis for Planning of Junctions (CAP-X) Tool. https://www.fhwa.dot.gov/software/ research/operations/cap-x. 2. Florida Department of Transportation (FDOT). FDOT-Modified CAP-X. http://www.fdot.gov/traffic/ TrafficServices/Intersection_Operations.shtm. 3. Virginia Department of Transportation (VDOT). VDOT Junction Screening Tool –VJuST. www.virginiadot. org/info/alternative_intersection_informational_design_guides.asp. Accessed March 27, 2019. 4. TRB. 2016. Highway Capacity Manual, Sixth Edition. Transportation Research Board of the National Acad- emies, Washington, DC. 5. Hummer, J. E., N. M. Rouphail, J. L. Toole, R. S. Patten, R. J. Schneider, J. S. Green, R. G. Hughes, and S. J. Fain. July 2006. Evaluation of Safety, Design, and Operation of Shared-Use Paths—Final Report. Report No. FHWA-HRT-05-137. FHWA, Washington, DC. 6. Mekuria, M., P. Furth, and H. Nixon. May 2012. Low-Stress Bicycling and Network Connectivity. MTI Report 11-19. Mineta Transportation Institute, San Jose, CA. 7. Tefft, Brian. 2011. Impact Speed and a Pedestrian’s Risk of Severe Injury or Death. Washington, DC: AAA Foundation for Traffic Safety. 8. Hummer, J. E., R. E. Montgomery, and K. C. Sinha. 1991. “Guidelines for Use of Leading and Lagging Left- Turn Signal Phasing.” Transportation Research Record 1324. 3, 11-20. 9. Schroeder, B. J., L. Rodegerdts, P. Jenior, E. Myers, C. Cunningham, K. Salamati, S. Searcy, S. O’Brien, J. Barlow, and B. L. Bentzen. 2016. NCHRP Report 834: Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities: A Guidebook. Transportation Research Board of the National Academies, Washington, DC. 10. Schultheiss, B., D. Goodman, L. Blackburn, A. Wood, D. Reed, and M. Elbech. February 2019. Bikeway Selection Guide. Report FHWA-SA-18-077. Federal Highway Administration, Washington, DC. 11. FHWA. 2009. Manual on Uniform Traffic Control Devices (MUTCD). U.S. Department of Transportation (USDOT), Washington, DC.

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Alternative Intersections and Interchanges (A.I.I.s) are designs that improve operations and safety for motorized traffic by strategically adjusting the geometric features at a given location, working on the general principle of redistributing motor vehicle demand at an intersection in an attempt to limit the need to add capacity with new lanes to improve traffic flow.

The TRB National Cooperative Highway Research Program's NCHRP Research Report 948: Guide for Pedestrian and Bicyclist Safety at Alternative and Other Intersections and Interchanges provides specific guidance for four common A.I.I.s: Diverging Diamond Interchange (DDI), Restricted Crossing U-Turn (RCUT), Median U-Turn (MUT), and Displaced Left-Turn (DLT).

These designs may involve reversing traffic lanes from their traditional directions, which may introduce confusion and create safety issues for pedestrians and bicyclists. In addition, pedestrian paths and bicycle facilities may cross through islands or take different routes than expected. These new designs are likely to require additional information for drivers, bicyclists, and pedestrians as well as better accommodations for pedestrians and bicyclists, including pedestrians with disabilities.

NCHRP 20-44(35) is the implementation project for NCHRP Research Report 948. The implementation project's objective is to share and disseminate the research results with public agencies and provide hands-on technology transfer assistance to these agencies. Find project outcomes, including webinars and training materials, on the implementation project page.

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