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APS home go to front of Accessible Pedestrian Signals
Go to Front page Background section Travel by Blind
Other Effects of APS
Blind Pedestrians' Access to Complex Intersections
Project 3-62 Guidelines for Accessible Pedestrian Signals
Comparison of two types of APS
Interfacing Accessible Pedestrian Signals (APS) and Traffic Signal Controllers
Wayfinding Technologies for People with Visual Impairments
Comparison of APS signal technologies
Rules & Regulations
Technologies and Features section Types
Walk Indications
Other Features
Choosing and Installing section Where to Install
Designing Installations
New Construction or Reconstruction
Retrofitting an Intersection with an APS
Installation Specifications
Field Adjustments
State of Practices section Case Studies
International Practice
Devices section Manufacturers
Selection Tool
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Downloads section Full Guide
Rating Scales
Field Adjustments

Common problems with APS in the U.S.

Key research
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.

ACB Survey

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.

AER Survey

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%

Reasons were:
  • They forgot which signal was associated with which crossing direction;
  • They didn't know which direction they were traveling; and
  • The intersection was not aligned with primary compass directions.
Uslan et al. (1988) found that on many trials blind participants failed in their attempts to cross streets because of indecision regarding the pole or button, even though all participants were fully familiar with the "bird call" signal, they knew what to listen for at each intersection, and they could listen through as many cycles as they desired. Sometimes participants first located the incorrect button and subsequently located and pushed the correct button after waiting and listening through one or more cycles.

Confusion of tones with other sounds
AER and ACB surveys confirmed that blind pedestrians really do confuse the sounds of birds with APS sounds.

ACB Survey

Crossed the street with an actual bird:     4%

Didn't cross because they thought the signal was a bird:     3%

AER Survey

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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