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19 For any signal installation, the use of APSs is essential to ensure judgments during peak hours than during off-peak hours. A that the signal is accessible to pedestrians who are blind. APS similar pattern was not found for sighted participants. The installations commonly feature a push-button locator tone to judgments of the blind participants improved, although they help pedestrians find the pedestrian push button, and an audi- remained risky, in a condition in which they made judgments ble signal or message that alerts the pedestrian when the walk at rush hour at simulated downstream crosswalk locations phase is shown on the pedestrian signal display. Audible sig- 60 ft from the actual crosswalks. nals include variations of nonverbal sounds (cuckoo, chirp, The work in Baltimore and Tampa involved making judg- or click) or a verbal message saying, for example, "Walk sign is ments about crossing without actually crossing. This left open on to cross [street name]." APS installations are a requirement the possibility that participants were using different judg- for all new or altered pedestrian signal installations in the draft ment criteria than would have been the case had they actually PROWAG by the U.S. Access Board (2005). crossed. To address this possibility as well as to follow up on Although they are common in the United Kingdom and several differences found in the earlier studies, the researchers other countries, pedestrian crossing signals at roundabouts are conducted a third study in Nashville at a high-volume, two- rare in the United States. If signals are used at roundabouts, lane roundabout. Blind and sighted participants made judg- they are often installed as a two-stage crossing to reduce vehi- ments without actually crossing during half of their trials and cle delays. In that case, a zigzag crossing geometry prevents crossed during the other half. The Nashville findings validated the pedestrian from inadvertently crossing the entire roadway the judgment-only measure, confirmed earlier findings, and without sufficient crossing time. Currently, pedestrian signals provided important new data about pedestriandriver inter- of varying types have been installed in the United States at action (Ashmead et al. 2005, Guth et al. 2005). A new measure only a handful of roundabout intersections, including Salt used in the Nashville study was the frequency of interventions Lake City, Utah; Charlotte, North Carolina; Clearwater Beach, by an O&M instructor who followed the participants during Florida; Alpine City, Utah; and Oakland County, Michigan. crossing trials. Although interventions occurred in only a small Further information can be found in Appendix B. percentage of trials (6%), the authors calculated a 99% prob- ability of a serious pedestrianvehicle conflict at this inter- section if a person who was blind crossed daily for 3 months. Blind Pedestrian A conflict was defined as a situation in which a crash is likely Crossing Experiments unless the driver or pedestrian takes immediate evasive action In studies at roundabouts completed with support from a and is synonymous with events that resulted in an O&M Bioengineering Research Program funded by the National intervention. Also, in post-experiment questionnaires, most Eye Institute (NIH 2010), researchers sought to document the participants who were blind reported that they would not street crossing behavior of people with total blindness at cross at this intersection if they had any other option. single- and multiple-lane roundabouts. In the initial study, An alternative to crossing in a gap in vehicular traffic is to conducted in 2000, adults who were totally blind and adults cross the street in front of a vehicle that has yielded upstream who were sighted made judgments at three Baltimore-area of the crosswalk. Geruschat and Hassan (2005) investigated roundabouts about whether gaps in vehicular traffic were the likelihood that drivers would yield to individuals holding crossable, or were long enough to permit crossing to the a white cane and standing at a roundabout crosswalk, and splitter island before the arrival of the next vehicle without contrasted these yielding data to data associated with indi- assuming any vehicular yielding. Trials were conducted at viduals without white canes standing in the same location. both exit-lane and entry-lane crosswalks of single-lane and This study, completed in Annapolis, MD, revealed that yield- two-lane roundabouts. Overall, blind participants were about ing rates overall were low, and varied as a function of vehi- 2.5 times less likely to make correct judgments than sighted cle speeds. Lower speeds were associated with higher yielding participants, took significantly longer to detect crossable gaps, rates. The presence of the long cane resulted in only a modest and were more likely to miss crossable gaps altogether. Fur- increase in yielding rates. Also, when drivers yielded to a blind ther, the errors of blind participants were much more likely pedestrian, the pedestrian was often unable to detect the pres- to be high risk than the errors of sighted participants at the ence of the stopped (yielding) vehicle and would subsequently two roundabouts that carried moderate and high volumes often fail to take the crossing opportunity provided. Yielding of traffic, in contrast to data collected at the lower volume rates were higher at roundabout entry lanes than exit lanes. roundabout. This research is reported in Guth et al. (2005). Inman, Davis, and Sauerburger (2005) reported that the mean This research team also investigated judgments of gaps at a observed time before vehicles yielded in both lanes was 63 s. single-lane roundabout in Tampa, Florida, with large and Inman, Davis, and Sauerburger (2005) reported the results predictable variations in traffic volume over the course of the of two studies related to the effectiveness of pavement treat- day (Long et al. 2002). Blind participants made more high-risk ments. Their first study, conducted on a closed course, was to