Some signalization schemes, such as exclusive pedestrian phasing and split phasing, need careful adjustment and consideration to avoid confusing pedestrians who are blind. Crossings with pedestrian signals that Rest-in-walk may need special treatment.
These issues must be considered in the design phase in determining type of device and location. In addition, careful adjustment of APS volume after installation is essential.
At a location with split phasing, an APS that can be heard from the parallel crosswalk provides incorrect, confusing, and dangerous information. It is critical that the WALK indication be audible only from the ends of the crosswalk being signaled so pedestrians do not begin to cross at a time when vehicles are turning across their path in a protected vehicular movement.
This can be accomplished by locating the APS very close to the crossing location so pedestrians can readily determine which is their signal. Careful adjustment of the APS volume at all times of the day and night is critical, as well as careful aiming of the speakers. Audible beaconing may not be appropriate at locations with split phasing, due to the possibility of confusion of signals.
In some timing plans for actuated turn phasing, traffic in one direction may be held longer to allow the opposing traffic to complete left turning movements. In many such cases, the pedestrian phases on parallel crosswalks begin at different times. An APS that can be heard from the parallel crosswalk provides incorrect, confusing, and dangerous information and could mislead a pedestrian to cross when vehicles are turning across their path in a protected vehicular movement.
Exclusive pedestrian phasing (also known as scramble phasing) makes it difficult for pedestrians who are blind or visually impaired to recognize the onset of the Walk interval, particularly at locations where right on red is permitted. In addition, there is no vehicular flow to aid in crossing straight to the destination corner.
Ongoing research is evaluating strategies for APS installation at intersections with exclusive pedestrian phasing.
In some locations, pedhead mounted APS have been installed on all corners and two different sounds for different crossing directions have been set to sound during the WALK indication. This is not recommended, as it is confusing to all pedestrians, and the assumption of pedestrians who are blind may be that the signals are broken.
A pushbutton information message, followed by a WALK tone, will be used in a pilot project in Morgantown, West Virginia, at an intersection with exclusive pedestrian phasing, in association with a WALK tone. The pushbutton information message will be modeled after.
During the Walk interval, all pushbutton-integrated devices at the intersection will emit the same, rapidly repeating, tone. Only one APS may be installed on some corners, with a modified tactile arrow installed on the top of the device, with arrows pointing in two directions. See Morgantown Case Study.
An experimental location in San Diego provides eight pushbutton integrated APS with speech pushbutton information messages, and speech WALK messages ("WALK sign is on for all crossings") and a tactile guidestrip within each crosswalk.
At locations where the pedestrian signal to cross the minor street rests-in-Walk, the WALK indication would sound constantly for that crossing. In many locations, that might prove to be irritating to neighbors.
Some APS manufacturers provide a limit switch that limits the length of the audible WALK indication to seven or eight seconds, but recalls the audible and vibrotactile indications of the WALK, if the button is pressed when there is adequate clearance time remaining. Availability of that feature should be investigated in the installation planning.
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