Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
1 C H A P T E R 1 Introduction This report presents a guidebook for the application of crossing solutions at roundabouts and channelized turn lanes to assist pedestrians with vision disabilities. The accessibility of these two complex intersections forms is an important civil rights challenge in the United States that has broad potential implications for engineering practice in this country. Roundabouts are increasingly adopted by the transportation community in the United States because of their ability to process balanced and unbalanced traffic patterns, aesthetic appeal, relatively low operating costs, and, most importantly, their documented safety benefits (e.g., Rodegerdts et al., 2007; Robinson et al., 2000; Persaud et al., 2000). Similar to channelized turn lanes (CTLs), there are concerns about the accessibility of roundabouts, particularly for pedes- trians who are blind (U.S. Access Board, 2003). Crosswalks at roundabouts are typically not sig- nalized. Roundabout accessibility challenges have been documented through extensive research by Guth et al., 2005; Ashmead et al., 2005; Schroeder et al., 2011; and Guth et al., 2013, among others. CTLs are a common treatment at signalized intersections, intended to allow heavy right- turning movements to bypass the main intersection. Crosswalks at CTLs are often unsignalized in the United States, and pedestrians must therefore make crossing decisions based on their perception of adequate gaps or the presence of a yielding vehicle. Accessible pedestrian signals or other audible devices are typically not available at most CTLs. Accessibility challenges at intersections with CTLs have been documented by Schroeder et al., 2006, and Schroeder et al., 2011, among others. 1.1 Purpose and Scope The purpose of this guidebook is to present guidance for the application of crossing solu- tions at roundabouts and CTLs at signalized intersections for pedestrians with vision disabilities, including individuals with total blindness. The guidebook provides an accessibility assessment framework and a methodology for evaluating treatment alternatives for a proposed crossing. Guidance is provided based on the feasible range of geometric and traffic operational conditions under which similar treatments have been demonstrated to enhance accessibility. While engineers may be faced with retrofit applications, this guidebook focuses on solutions that can be incorporated in the design phase of a new project. Treatments would be fully imple- mented when a new intersection opens to traffic to ensure it is in compliance with the Americans with Disabilities Act (ADA) and its implementing regulations from the start. The guidebook also considers the trade-offs between the needs of various users of a facility: pedestrians, including those with vision impairments or other disabilities, bicyclists, and vehicular traffic, including heavy vehicles such as trucks and buses. Specifically, the guidebook relies on conveying key
2 Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities: A Guidebook principles for the accessibility of a roundabout or CTL, and translating these principles into performance-based checks that can be integrated in the design process for a new site. This guidebook does not entail any policy recommendations for accessibility, nor does it prescribe standards for accessibility of the intersection types discussed. Rather, the guidebook is intended to be used as a decision-support tool by practicing engineers and planners. Both the decision framework and the methodology are meant to assist agencies with setting their own standards. The guidebook enables accessibility evaluations based on empirically derived models and performance measures. Also, the guidebook can be used to assess the equivalent facilita- tion potential of various pedestrian access treatments in accordance with the ADA, but without specifying standards for equivalent facilitation or accessibility. 1.2 Accessibility Versus Safety The primary focus of this guidebook is on the accessibility of intersections for pedestrians with vision disabilities. While the safety of a facility and the access to a facility are related, the two terms are not synonymous. A facility may be considered safe if the frequency of crashes is low. However, accessibility must be judged by the extent to which any individual, or group of individuals, limits or avoids using a facility based upon a real or perceived belief that the facility is unsafe or extraordinarily difficult to use. Conversely, good accessibility is best evaluated through direct observation of pedestrians with disabilities using a facility without a significant degree of perceived risk beyond that experienced by sighted pedestrians. A facility that is not accessible to and usable by pedestrians who are blind or who have low vision will often be avoided and thus may appear safe due to the lack of crashes involving pedestrians. But little or no pedestrian exposure may be equally or more related to this lack of crashes, as with any safety performance of the intersection. Accessibility is therefore evaluated independently and in addition to the safety record of the intersection. A key motivation of this document is to provide agencies with tools for evaluating the accessibility of a facility, independent of pedestrian crash statistics. ADA is the underlying legislation that establishes access as a civil right. Requirements for accessibility in state and local government programs and services, including public rights-of- way, are outlined in the implementing regulations for Title II of ADA , which specify that any newly constructed or altered public facility shall be âreadily accessible to and usable by individu- als with disabilitiesâ (U.S. Department of Justice, 2010) including those with vision loss, mobility impairments, or other disabilities. The absence of recorded pedestrian crashes, especially those involving older pedestrians, chil- dren, or those with visual and/or physical impairments, does not constitute proof that a facility is accessible, nor does the presence of crashes constitute proof that it is inaccessible. An analysis of pedestrian crashes alone therefore is not sufficient to determine the accessibility of complex intersections to pedestrians who are blind. 1.3 Minimum Specifications and Equivalent Facilitation One of the responsibilities of the U.S. Access Board is to develop minimum technical speci- fications for transportation facilities to ensure that public rights-of-way are accessible to and usable by all people, and are thereby in compliance with ADA. The U.S. Access Board pub- lished a Notice of Proposed Rulemaking for Accessibility Guidelines for Pedestrian Facilities in the Public Right-of-Way (referred to as PROWAG-NPRM in this report) on July 26, 2011 (U.S. Access Board, 2011), outlining requirements for making crosswalks and intersections in the
Introduction 3 public right-of-way compliant with ADA. Specifically, paragraph R306.3.2 requires that, at roundabouts with multilane pedestrian street crossings, a pedestrian-activated accessible pedestrian signal (APS) complying with the Manual on Uniform Traffic Control Devices for Streets and Highways (referred to as MUTCD in this report), Sections 4E.08 through 4E.13 (MUTCD, 2009), be provided for each multilane segment of a pedestrian crossing, including the splitter island. A pedestrian-actuated and APS-equipped signal thereby satisfies the acces- sibility requirement for two-lane roundabout approaches. PROWAG-NPRM R306.4 and R306.5 language for two-lane CTL crosswalks is very similar to the language for two-lane roundabouts, in that a pedestrian signal with APS makes the crossing accessible. PROWAG-NPRM also requires and specifies a continuous and detectable edge treatment at roundabouts where sidewalks are flush against the curb and pedestrian crossing is not intended (R306.3.1). These edge treatments are designed to reduce the likelihood that individuals with vision impairments cross at locations other than marked crosswalks. Advisory R306.3 describes additional features to delineate the crossing locations at roundabouts. APS devices are required at all crossings equipped with pedestrian signals (R209), and truncated dome detectable warn- ing surfaces are required on the curb ramps to demark the street-sidewalk boundary (R208.1). PROWAG-NPRM does not address crossing treatments or signalization at single-lane round- abouts or single-lane CTLs. While PROWAG-NPRM specifies a pedestrian-actuated signal at two-lane roundabout cross- walks with pedestrian facilities, ADA allows equivalent facilitation in all implementations of requirements. PROWAG-NPRM allows for equivalent facilitation in Section R102, and defines equivalent facilitation as follows: The use of alternative designs, products, or technologies that result in substantially equivalent or greater accessibility and usability than the proposed guidelines is permitted. Consequently, treatments or geometric configurations that provide equivalent accessibility to treatments or configurations specified in ADA and its implementing regulations are acceptable and in compliance with ADA. This is to allow for improvements in technology, developments in materials or research, or the implementation of new ideas and information. It is up to the designer and/or constructing jurisdiction to provide justification for their installation decisions in the case of an ADA complaint. One of the principal goals of this document is to assist trans- portation agencies with evaluating the equivalent facilitation of a particular treatment, and to decide whether its provision is likely to conform to ADA. 1.4 Four Components of the Crossing Task The crossing task for blind pedestrians consists of four principal tasks that need to be mastered to successfully cross the street at roundabouts and intersections with CTLs: ⢠Finding the crosswalk and identifying the intended crossing location, which includes identifying when and where to turn from the sidewalk toward the crosswalk landing, ⢠Aligning to cross to establish a correct initial heading at a crosswalk that may or may not be aligned perpendicular with the sidewalk or in the same direction as the slope of the associated curb ramp, ⢠Deciding when to initiate crossing in an environment of largely uninterrupted traffic flow, requiring the identification of appropriate gaps in traffic or crossing opportunities in front of yielding vehicles (when signals are provided, an audible message should be used to convey to a blind pedestrian when the walk indication is active), and ⢠Maintaining correct heading while crossing multiple lanes over the length of the entire crosswalk and staying within the crosswalk until the far side of the roadway is reached.
4 Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision Disabilities: A Guidebook The crossing task at CTLs and roundabouts is often challenging for persons with vision impair- ments due to the prevailing curved vehicle paths and movement of other nearby vehicles. The task of correctly identifying vehicle positions and trajectories, vehicle gaps, and driver yielding based upon auditory information alone is challenging. The geometric configuration of the intersection can further result in elevated speeds at the crosswalk and heavy traffic volumes can contribute to high ambient noise levels. These factors can also significantly impact crossing difficulty for persons with vision impairments. Three aspects of the four components of the crossing task are typically characterized as way- finding tasks: finding the crosswalk, aligning to cross, and maintaining correct heading while crossing. Difficulty in these tasks may result in persons with vision impairments initiating cross- ing outside the crosswalk area, crossing to the central island of a roundabout, or missing the island at a CTL due to veering. These and other wayfinding challenges can cause confusion and disorientation for the pedestrian. Crossing at a location that is not within the crosswalk and thus where drivers are not expecting pedestrians can be a safety issue as well. The other component of the crossing task, deciding when to cross, can be more difficult than at a conventional, orthogonal intersection because of the difficulty in interpreting traffic patterns. Traffic sounds are typically the most reliable crossing-related information avail- able to individuals with vision impairments at conventional intersections. When pedestrian crossings are signalized, the addition of an APS, along with traffic sounds, can provide fur- ther information to a blind traveler about the location of the pushbutton and the status of the pedestrian signal. The audible information from the accessible pedestrian signal enables pedestrians who are blind to locate the pushbutton, to detect the onset and duration of the walk interval, and to anticipate accurately when vehicles are likely to stop to permit pedestrians to cross. Recent research on the crossing performance of people with vision impairments at complex intersections, including roundabouts and CTLs, demonstrated that there are unique challenges for this population (Ashmead et al., 2005; Guth et al., 2005; Schroeder et al., 2011). The traffic control at a roundabout entry leg is typically a yield sign, and many drivers are able to enter the circulatory roadway without coming to a full stop or slowing or stopping at the crosswalk. Similarly, traffic exiting the roundabout is often free flowing, resulting in largely uninterrupted traffic flow at the exit crosswalk. Traffic patterns at CTLs are similar in many cases in that the right-turning movement is largely free flowing. The design of a CTL and the location of the crosswalk, whether marked or unmarked, can vary significantly across sites (NCHRP Report 279; Newman, 1985). However, recent national survey research revealed that about 70% of CTLs have crosswalks located in the center of the channelized lane (NCHRP Web-Only Document 208; Potts et al., 2011). That same research emphasized the importance of design consistency to facilitate crossing and wayfinding task performances by pedestrians who are blind. Crosswalks at both types of facilities are typically not signalized, and the task of identifying crossing opportunities is thus unassisted by technologies that provide audible information to pedestrians. Depending on the geometric design and the location of the crosswalk, vehicle speeds may be relatively high and, as noted earlier, the interpretation of the sounds of vehicle movement is complicated because the vehicles are moving on a curving path (Ashmead et al., 2005). At conventional signalized intersections, two traffic streams typically move perpendicu- lar to each other, making it easier for pedestrians who are blind to interpret directional traffic movements using hearing alone. Finally, the continuous flow of traffic circulating the round- about or moving through the CTL and main traffic streams of the intersection can create a difficult auditory environment, and the listening task is complicated by the elevated levels of ambient noise.
Introduction 5 1.5 Outline of the Document This chapter has provided a general overview of the guidebook and of accessibility challenges for pedestrians who are blind at roundabouts and CTLs. The remainder of the document is organized as follows. Chapter 2 introduces a design process for roundabouts and CTLs, highlighting where analysts can integrate an evaluation of intersection accessibility with references to specific evaluation components presented in other chapters. Chapter 3 presents a discussion of the general principles for pedestrian access. This chapter contains a summary of wayfinding and alignment principles, a more detailed discussion of the crossing challenges faced by pedestrians who are blind, and guidance on treatments to facilitate accessibility of roundabouts and CTLs for blind pedestrians. Chapters 4 and 5 present the principles for pedestrian access at roundabouts and CTLs, respectively. The chapters contain discussion of pedestrian-focused designs, crosswalk location and angle, and use of traffic control devices at these locations. Chapters 6 and 7 provide assessment methodologies for evaluating the accessibility of round- abouts or intersections with CTLs. Chapter 6 provides methods and guidance for assessing wayfind- ing and alignment treatments at both facility types for a given design. Chapter 7 presents a crossing assessment methodology for evaluating crossing risk, crossing delay, and a crossing confidence score based on various input variables. The chapter also provides guidance on assessing sight distance, visibility, and audibility of designs and any traffic control devices used at the crosswalk. The main chapters are supported by two appendices that offer supplemental but important information. Appendix A offers additional discussion of noise impacts on accessibility, since the audible environment was found to be a key consideration in the evaluation of a crosswalk. Appen dix B - presents an assessment of selected accessibility treatments, including a treatment descrip- tion, estimate of installation cost, and field test results for application to roundabouts and CTLs. The appendix includes detailed cost estimates for several of these treatments.
