Each installation requires engineering judgment. In planning for APS installation, consider the following in determining the type of APS and where and how to install it:
General principles in the decision:
In many cases, a municipality or state will wish to purchase one type of APS device for all installations. However, there are engineering and design decisions in installation of APS as well as in the choice of equipment. When retrofitting intersections with APS, it may be necessary to use different types of APS, or different options on the same type of device, to provide unambiguous information at different intersections.
In new construction or reconstruction, where the APS can be located consistently, it is possible to use a standardized device and mounting location.
Device locations are critical to functioning of the APS and need to be planned. The APS may provide ambiguous information if located incorrectly, just as pedestrian or vehicular signal heads can provide ambiguous, or even dangerous, information if located incorrectly.
Considerations for locating pushbuttons and speakers
When locating pushbuttons and speakers, consider their relation to:
Relation to crosswalk and pedestrian waiting location
Pedestrians who are blind or visually impaired must be able to quickly and accurately perceive which crosswalk is being signaled by an audible WALK indication. The use of two different sounds for crossing in two different directions has not proven to provide unambiguous information. (See section in Research and Walk Indication).
Unless the sound sources are separated by at least 10 feet and located appro-priately in relation to the crosswalk, it is difficult to discriminate which device is sounding. (See additional information on speaker location.)
The ADA does not require wholesale reconstruction and renovation, but it does require municipalities to begin to address and prioritize retrofitting facilities to newer standards.
Location in relation to curb ramps and landings
At pedestrian-actuated crossings, the pushbutton should be located close to the level landing of the curb ramp serving that crossing, for the convenience of all pedestrians using the pushbutton. For this reason, PROWAAC recommended specific locations for pushbuttons:
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This site was developed under the sponsorship of the National Cooperative Highway Research Program.