ACB and AER surveys noted in above section
Uslan, Peck and Waddell (1988), in research in Huntington Beach, CA, compared crossings by blind pedestrians at three intersections having "bird call" signals and one control intersection without APS.
Problems with volume
ACB and AER surveys reported the experience of pedestrians with visual impairments in using APS that had "bird call" signals, bells and buzzers. There were problems both with APS being considered too quiet and too loud.
Too quiet: 71%
Too loud: 45%
NOTE: Totals do not add to 100%. Some respondents sometimes found APS to be too quiet, and at other times found them to be too loud.
Too quiet: 52%
Too loud: 24%
Uslan et al. (1988) found that at one intersection with split phase timing, where the bird call signals for parallel crosswalks had separate timing, three of 15 blind participants initiated their crossings with the signal for the parallel crosswalk, walking into the path of left-turning vehicles. This is an example of a specific type of problem with signal volume.
Problems with ambiguity
ACB and AER surveys looked particularly at data from blind pedestrians and O&M; specialists from California, whose experience with APS is almost exclusively with "bird call" signals that are intended to provide unambiguous information regarding which street have the Walk interval. Many respondents indicated that they or their students sometimes did not know which crosswalk had the Walk interval. ACB - 68%; AER - 72%
Confusion of tones with other sounds
AER and ACB surveys confirmed that blind pedestrians really do confuse the sounds of birds with APS sounds.
Crossed the street with an actual bird: 4%
Didn't cross because they thought the signal was a bird: 3%
Crossed the street with an actual bird: 11%
Didn't cross because they thought the signal was a bird: 10%
Problems with beaconing
ACB and AER surveys indicated that pedestrians who are blind are sometimes not able to localize the sound of an APS in order to use it for guidance across the street. ACB - 6%; AER - 39%.
Problems locating pushbuttons
Uslan et al. (1988) found that the major problems 27 legally blind participants had with "bird call" type APS, were in locating the pole and the pushbutton, and determining which pushbutton was for which crosswalk. Participants traveling with dog guides experienced the most difficulty locating the pole.
As noted above, AER and ACB surveys also identified problems with locating the pushbuttons.
Confusion across intersections
When APS are too loud, and are at intersections that are close together, the APS for one intersection may be heard from another, leading some pedestrians to incorrectly think they have the Walk interval. The surveys indicated the extent of this problem. ACB - 19%; AER 25%.
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