Cover Image

Not for Sale



View/Hide Left Panel
Click for next page ( 95


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 94
94 way and entering the vehicular way. Also, planting strips along blind pedestrians that the intersection is a roundabout. When the sidewalk serve as a barrier that discourages pedestrian access the sidewalk is paved to the curb, blind pedestrians may assume to the roadway at places other than the crosswalk and make it they are at a rounded corner and cross at the point where they less likely that a blind pedestrian will inadvertently step from detect a curb roughly in front of them, which would result in the paved walkway into the paved roadway at any point other them crossing the circulatory roadway. However, many pedes- than the crosswalk or begin crossing from the wrong point trians who are blind prefer to travel near the edge of a sidewalk without realizing the intersection is a roundabout. They also that is furthest from the street. In this case, unless they are specif- provide a trailing surface that long cane users can use to locate ically looking for a non-corner crossing, they may not be aware the crosswalk. of either a break in a landscaping strip or a curb ramp. For those The splitter island should be wide enough for pedestrian who travel using guide dogs, detecting the break in a landscap- refuge and to enable a true two-stage crossing. Several blind ing strip or a curb ramp requires the use of special strategies. pedestrians commented that the landscaping and trees on the Two treatments are currently suggested for providing effec- splitter island blocked some of the sound from the lane behind tive cues to the location of crosswalks that are not where they them when they were crossing from the island to the curb. This are expected. At a crossing with an accessible pedestrian sig- helped with sound separation and discrimination of the traffic nal, placement of the pushbutton with its pushbutton locator coming toward them from the traffic going away from them. tone immediately beside the curb ramp leading to the cross- Landscaping on the splitter islands should not block the view walk provides an audible cue to the presence and location of a of the crosswalk for drivers. crosswalk. This feature was noted by pedestrians during the Additional physical separation of the crosswalk from the Golden two-lane roundabout posttest with the PHB. A 24-in.- circulating lane may be considered in the design of the two- wide strip of a linear texture, sometimes referred to as a "bar lane roundabout to separate driver decision points and to tile," running perpendicular to the sidewalk and across the provide added queue storage at the exit leg for yielding drivers. entire width of the sloped ramp, provides a tactile cue that However, a crosswalk too far from the circle may lose the can be detected underfoot and by use of the long cane. Use roundabout's traffic-calming effect, which reduces speeds and of linear textures is uncommon in the United States at pres- encourages yielding. Low design speeds and traffic-calming ent but has been required or is commonly used to guide pedes- treatments may mitigate that tradeoff. trians who are blind to crosswalks in other countries (Bentzen, Barlow, and Franck 2000). The task of properly aligning to cross can be assisted by a Wayfinding and "square" geometry. At a conventional four-legged intersection, Alignment Treatments blind pedestrians can often align using the cues of adjacent and This research was primarily focused on the aspect of acces- perpendicular traffic. Since traffic patterns at roundabouts sibility that is related to the actual decision of when to initialize and channelized turn lanes are on curved trajectories, addi- a crossing. As discussed earlier in this report, the full accessi- tional alignment cues may be needed. Directional tactile sur- bility of a crossing involves three other critical tasks: (1) locat- face lines that are accessed by foot and installed concurrent ing the crosswalk, (2) aligning to cross, and (3) maintaining with detectable warnings have some potential, as do returned alignment during crossing. Several treatments are available curb installations that provide a hard edge on each side of the that can assist in these important accessibility tasks. Ongoing crosswalk ramp that is in line with the direction of travel on research for the NIH (2010) is currently comparing the effec- the crosswalk. Another potentially effective treatment option tiveness of various wayfinding and alignment treatments. involves presenting an auditory signal from the far side of the However, even today anecdotal evidence suggests that certain crosswalk (for example, through an audible device). A far-side facility design elements and supplementary treatments can be audible signal could also be expected to assist with the task valuable assets to blind travelers. of maintaining alignment during crossing. Other alignment The task of locating crosswalks at roundabouts and CTLs treatments are raised markings that delineate the crosswalk or is challenging because crosswalks in these situations are not guidance strips that can be raised parallel to the crosswalk. located at corners. Unless pedestrians who are blind are aware The Access Board draft PROWAG and other U.S. Access that they are approaching a roundabout or CTL crossing, it is Board resources provide additional detail on these and other common for them to continue around the bend without real- wayfinding and alignment treatments. The reader is encour- izing for some time, if at all, that they have gone past the aged to refer to these references for further information. crosswalk. This is true both for those who travel using a long cane and those who use guide dogs. Design elements that help Future Research Needs pedestrians locate the crosswalk are landscaping along the curb except at the crosswalk, and the presence of a curb ramp This research provided a proposed framework for pedes- at the crosswalk. This landscaping also may provide a clue to trian accessibility and presented field study results and other

OCR for page 94
95 material to inform the ongoing nationwide discussion of the mining that an intersection is a roundabout, locating the cross- accessibility of roundabouts and CTLs. Clearly there are lim- walks, aligning to cross, determining a safe time to cross, and itations to this research, which are most notably tied to the maintaining alignment while crossing. Developing a training number of sites that could be captured in the field studies. program that could be used by O&M specialists and supported The number of roundabouts in the United States has grown by state DOTs may be a direction to explore further. over the course of this project. When the project team was Future research should perform field testing of additional looking for sites, we had difficulty finding roundabouts with two-lane roundabout treatments. In particular, more testing appropriate features, in areas where there were adequate num- is needed to determine under what conditions (geometry, traf- bers of blind pedestrians, and in municipalities that were inter- fic) a particular treatment is most appropriate. This research ested in testing various treatments. Now there are examples identified two treatments (raised crosswalk and pedestrian of roundabouts in various locations with some features that hybrid beacon) that showed good potential at the tested two- may address accessibility for pedestrians who are blind, for lane roundabout. These findings should be validated with addi- example, yellow pedestrian-actuated beacons installed at the tional testing, including some at higher-volume roundabouts. Bird Rock corridor roundabouts in the San Diego area, and Since the potential signalization of two-lane roundabouts is other municipalities that are considering the installation of a politically sensitive topic, additional research would give PHBs and raised crosswalks. An ADA-complaint/legal action in engineers, policy makers, and the U.S. Access Board a more Oakland County, Michigan, resulted in court-ordered testing complete understanding of the crossing challenges. In partic- of treatments at two three-lane roundabouts. This study and ular, research may get closer to developing actual require- other activities will provide additional information, which in ments and thresholds for the installation of pedestrian signals combination with results of NCHRP Project 3-78A, can give at two-lane roundabouts with the objective of enhancing the more guidance and comparisons for evaluation of treatments accessibility and usability to pedestrians who are blind. In addi- in other locales. But there is much more that needs to be tion, more research should be done to test low-impact treat- explored in developing crossing solutions for pedestrians with ments at low-volume two-lane roundabouts. Future studies vision disabilities at roundabouts and channelized turn lanes. should evaluate the use of, for example, rectangular rapid- This research showed serious accessibility problems at the flashing beacons (RRFBs) and other flashing beacons, as well selected CTL site and that the low-cost/low-impact treat- as traffic-calming treatments that are more suitable for cold ments were not sufficient to establish accessibility at that site. climates or other regions where raised crosswalks may not be Since the number of CTLs currently far outnumbers round- allowed in public rights of way. abouts, additional research is needed that field tests treat- While some of the tested single-lane roundabout crossings ments at CTLs and further investigates issues at different CTL may be deemed accessible under prevailing traffic conditions, designs. Specifically, two additional CTL studies are proposed: the analysis did point to some areas of concern, including (1) testing of a traffic calming treatment such as the raised unexpectedly high delays at one low-volume site (DAV-CLT) crosswalk or a pedestrian hybrid beacon at high-volume and and high interventions at a high-volume location (PS-RAL). high-speed locations, and (2) testing of low-cost treatments The team believes that low-cost treatments could enhance blind (sound strips and flashing beacons) at low-volume and low- pedestrian access at these locations. Future tests should explore speed locations. This additional research would greatly aid the the impacts of traffic-calming treatments (e.g., raised cross- understanding of crossing challenges at CTLs and would lead walks) and auditory treatments such as sound strips. Flashing to the development of a more extensive treatment catalogue beacons may further improve driver awareness of pedestrians for these locations. and promote yielding in the right environments, and more As discussed earlier in this chapter, little is known about research could clarify where treatments are most useful. the impact of education and training on the behavior of blind In addition, there is a need for new and improved field- pedestrians, and little is known about how different move- based risk performance measures to provide a more objective ments or crossing strategies of pedestrians who are blind might and consistent assessment of risk and safety. The NCHRP affect driver behavior. Both could be fruitful areas for more Project 3-78A analysis was limited to the use of O&M interven- exploration and research. First, the team observed a number tions as a measure of pedestrian risk, which from an analysis of different techniques used by blind pedestrians in crossing, perspective has the drawback of being a relatively rare event. getting the attention of drivers, and detecting yields, but at this The availability of a more readily observed and continuous point it is unknown what strategies and techniques work best. measure of risk could facilitate the development of safety pre- Second, there is a need for training programs for pedestrians diction models (similar to the mixed-priority delay models) who are blind, although there is currently no consensus on the and could further guide the process of surrogate safety assess- form and extent of this training. Consequently, there is a need ment in simulation. Potential new risk measures include the for determining effective strategies and techniques for deter- time-to-collision measured at the time a pedestrian steps into

OCR for page 94
96 the crosswalk or the necessary deceleration rate of vehicles to occur somewhere on the continuum between these very quiet come to a stop prior to the crosswalk. Chapter 6 discussed and very loud conditions, and it is unclear what types of sound some initial efforts and demonstrations showing that it is feasi- environments and cues are most difficult or most helpful to ble to obtain these data from field and/or video-based measures the blind pedestrian. (Schroeder 2008), and work is currently underway in applying In closing, significant work remains to be done in this area these concepts to multi-lane roundabouts (NIH 2010). that focuses on additional treatments, and most importantly, A field-based validation of the mixed-priority delay models on extending these findings to more locations that are differ- and work toward extending these models to data from addi- ent geometrically and/or from a traffic operational perspective. tional sites would provide greater confidence in the modeling. This report has established a framework and analysis method- Due to the limited data available in this research, all observa- ology that is readily extended and applied to other sites and tions were used for model development. If the models were that will allow future research efforts to be tied directly to validated against other sites, analysts would likely have much findings from this report. The ongoing national debate on the increased confidence in their viability. accessibility of modern roundabouts and CTLs has spurred Finally, future research should include an increased focus municipalities to take the initiative and tackle some of these on the auditory environment in the vicinity of the crosswalk accessibility issues prior to the completion of this report and to gain a better understanding of the relationship of traffic vol- prior to the final adoption of PROWAG. Additional research umes, associated noise patterns, and ultimately the challenges should take advantage of this momentum and perform con- to blind travelers to identify crossing opportunities based on trolled pretestposttest evaluations at these locations as treat- auditory cues. Anecdotal evidence from this research suggests ments are being installed. A significant amount of time in this that pedestrians are able to readily cross during all-quiet peri- project was devoted to selecting treatments and identifying ods while hesitating or waiting during times of high ambient municipalities willing to install them for study. With already- noise, although this strategy raises concerns in light of more planned installations, additional research can make very effi- frequent occurrence of quiet (hybrid) vehicles (Wall Emerson cient use of project resources by focusing on the field studies and Sauerburger 2008). However, most crossing situations and data analysis of these locations.