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Research
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Technologies and Features section Types
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Choosing and Installing section Where to Install
Designing Installations
Intersection geometry considerations
New Construction or Reconstruction
Retrofitting an Intersection with an APS
Installation Specifications
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Glossary
 

Installation decisions

Introduction
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
  • Need for audible beaconing
  • Signal phasing
    - Split phasing
    - Actuated turn phasing
    - Exclusive pedestrian phasing
    - Rest-in-walk
  • Intersection geometry
    - Unsignalized right turn lanes and splitter islands
    - Signalized right turn lanes
    - Medians
More latitude in specifications may be applied when the APS is an addition to an existing intersection. ADA requires new construction to meet the guidelines, while it requires additions to meet the guidelines to the maximum extent feasible. Understanding basic considerations is necessary to designing usable installations in both new and retrofit situations.

Principles
General principles in the decision:
  • Provide information to pedestrians about the presence and location of pushbuttons if pressing a button is required to actuate pedestrian timing.
  • Provide unambiguous information about the WALK indication and which crossing is being signaled.
  • Use audible beaconing only where necessary:
    - Put as little additional sound in the environment as possible;
    - Avoid disturbance of neighbors; and
    - Allow pedestrians who are blind or visually impaired to hear the traffic sounds, as well as the APS.
Type and features
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 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:
  • Crosswalks and pedestrian waiting location; and
  • Curb ramps and level landings.
Consider the following factors:
  • Location of mounting pole
  • Type and shape of mounting pole.
Research currently underway will provide additional information about separation of poles, use of different types of devices, and speaker locations. More guidance will be provided at the completion of NCHRP Project 3-62, of which this guide is part.

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:
  • "When located at a curb ramp [having the required level landing at the top], the push button shall be placed within 24 inches (610 mm) horizontally of the top corner of the curb ramp, on the side furthest from the center of the intersection of the roadway.
  • When located at a transition ramp, the push button shall be placed adjacent to the lower landing." (PROWAAC X02.5.1.3(F))
PROWAAC recommended APS zones are included in Figures X02.5A, B, C in the document EXISTING PROWAAC GUIDANCE ON APS.

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