Research on source of WALK signal
Signals that have been typically installed in the U.S. have provided a loud beaconing WALK indication simultaneously from both ends of the crosswalk, and usually from two parallel crosswalks at the same time. As shown in the ACB and AER surveys, pedestrians who are blind often have difficulty if they try to use the APS to indicate the direction of travel on the associated crosswalk. Research has taken place in Canada, Japan, and the U.S. on the effect of source of the WALK signal on accuracy of aligning to cross and of making actual crossings.
Results of research
Presentation mode — simultaneous, alternating, and far side
Stevens (1993) and Tauchi, Sawai, Takato, Yoshiura and Takeuchi (1998) tackled the problem of improving localization of WALK signals (beacons) by varying the source of the sound. They found that blind pedestrians could cross more quickly and with less veering when the WALK signal alternated back and forth from one end of the crosswalk to the other.
Laroche et al. (2000) confirmed the superiority and subjective preference for an alternating signal for beaconing at a simulated intersection, but found no advantage of the alternating signal when data were collected at an intersection with steady traffic on both streets. This was true for all tones tested (chirp, cuckoo, low cuckoo, and melody). It may have been that blind participants had good directional information from vehicular sound at the intersection or it may have been related to the shorter duration of the APS sound when installed at the intersection. In the previous testing at a simulated intersection (in quiet), the WALK signal continued for 36 seconds, more than the time required for participants to complete the entire crossing. Testing at the simulated intersection was also in a quiet environment.
Poulsen (1982) reported more accurate walking in a simulated crossing setting with a far end signal, than when a signal came simultaneously from both ends, and that far end signal was regarded favorably by a group of blind pedestrians in a field test at a real intersection.
Tauchi, Takami, Suzuki, Kai, Takahara, and Jajima (2001) examined the effects of alternating WALK signals in which the sounds from both ends of a 60 ft. long crosswalk at the top of a "T" intersection with alternating WALK signals were different. Participants were better aligned, and maintained alignment better with the APS with different tones at the end of the crosswalk than with the APS having the same tone at the end of the crosswalk.
Wall et al. (2004) compared the usefulness of auditory signals in guiding crossing behavior in three signal presentation modes, simultaneous, alternating and far side only. In several experiments, blind adults and blindfolded sighted adults crossed a simulated crossing with recorded traffic noise to approximate street sounds. Audible signals were presented simultaneously from both ends of the crosswalk, alternating from one end to the other, or from the far end of the crosswalk only. The signals continued only for the typical U.S. WALK interval of seven seconds, stopping when participants were approximately halfway across the simulated street.
The principal findings were the same for blind and sighted participants and applied across a range of specific signals (e.g. chirps, clicks, voices). Crossing was more accurate when audible signals came only from the far end of the crossing, rather than the typical practice of presenting signals simultaneously from both ends. Alternating the signal between ends of the crossing was not helpful. However, providing a locator tone at the end of the crossing during the pedestrian clearance interval improved crossing accuracy. These findings offer less promise for the usefulness of the alternating signal mode, especially when the findings for single vs dual crosswalks are considered. In previous studies, only one crosswalk was signaled, but this research compared signaling a single crosswalk versus two parallel crosswalks in two experiments. Errors were lower in the alternating mode than the simultaneous mode, but only when a single crossing was signaled. The customary practice of signaling two parallel crossings at the same time seemed to draw participants somewhat toward the center of the intersection.
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