2006 Conference General Sessions




Michael Williams
U.S. Dept. of Veterans Affairs
Atlanta VAMC

1670 Clairmont Rd. (151R)
Decatur GA 30033
Day Phone: 404-414-1507

Fax: 404-728-4837

Email: mike2488@yahoo.com

In order for visually impaired individuals to cross streets independently, they must be able to recognize that they have arrived at an intersecting street; determine the configuration of the intersection so that they can establish an optimal location, heading, and employ a reliable and safe procedure for crossing. It is also helpful to be able to determine or confirm the name of the intersecting streets. When intersections are familiar, some of this information may already be known. Much of this information is typically obtained by listening to traffic patterns and sounds of individual vehicles. Techniques and cues used in crossing streets are diverse and vary by location and individual. Many visually impaired pedestrians have received mobility instruction from an orientation and mobility (O&M) specialist to use a cane and/or dog guide to travel independently. In the most common technique utilized for crossing at signalized intersections, pedestrians who are blind begin to cross the street when there is a surge of traffic parallel to their direction of travel. Vehicular
sounds are often sufficient to determine the onset of the WALK interval and the direction to the crosswalk on the opposite side of the street. A large number of travelers who are blind cross streets safely and independently most of the time. Nonetheless, there are many intersections that blind individuals consider to be unsafe for crossing without the assistance of a human guide. Individual differences in impairments, mobility skills, abilities, and personality as well as the environmental situation determine which streets any individual will choose to cross independently.

The effects of two types of accessible pedestrian signals on the street crossing behavior of 24 totally blind participants were directly compared in this research. One accessible pedestrian signal CAPS) used a sound generator and vibrating hardware, which were integrated into the pedestrian push button (Polara). These sounds were heard from the near vicinity of the push button, and a different message or repetition rate was used to indicate the WALK interval. The second ASS used pulsing LEDs to illuminate the message in the pedestrian signal headcombined with an IR beacon to transmit a message to a hand held receiver carried by the blind traveler (Relume). The hand held receiver provided a “Walk” or “Wait” message designated by variable tones, which was only audible to the user. A control condition consisted of crossing without any ASS device. Data were collected on: crossing speed; latency from the start of the walk and entering the crosswalk; the number of cycles missed and accuracy of the crossing. A within subjects design was employed with crossing randomized for condition, direction of crossing. The treatments were placed at two adjacent intersections for the first half of the participants and then switched for the second half of the participants to eliminate a location effect.

Results indicated that the time to cross the street was significantly shorter when participants used the hand held device then when they used the audible push button device or crossed without any ASS. There was no significant difference in crossing time between the audible push button device and the control condition. Crossing time with the audible push button device did not differ significantly from crossing time without any ASS device. Latency to start crossing was significantly faster when participants used the handheld device than either the audible push button or when crossing without an ASS in the control condition. The audible push button device was also associated with a significantly shorter latency than the control condition. Data on the accuracy of the crossing indicated much greater variation in crossing accuracy with the audible push button device than with the hand held device or control condition. The number of missed cycles was significantly lower with both ASS devices than when the person crossed without an ASS and there was no difference between either ASS device. An equal percentage of participants (45%) favored each of the two ASS devices and 5% preferred both equally while 5% favored crossing without either of the ASS devices.

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Reprinted with author(s) permission. Author(s) retain copyright