walkinginfo.org Logo Go to contents of page
APS home go to front of Accessible Pedestrian Signals
Go to Front page Background section Travel by Blind
Rules & Regulations
Technologies and Features section Types
Walk Indications
Other Features
Choosing and Installing section Where to Install
Designing Installations
New Construction or Reconstruction
Retrofitting an Intersection with an APS
Installation Specifications
Field Adjustments
State of Practices section Case Studies
International Practice
Devices section Manufacturers
Selection Tool
Product Matrix
Downloads section Full Guide
Rating Scales
Field Adjustments

Location of controller boards and wiring

All APS currently on the market are wired to the pedestrian signal indications. The addition of APS does not change the signal timing.

Pushbutton-integrated devices generally require an extra set of wires to the pushbutton to power the audible indications. APS with actuation indicators may need to receive an actual signal from the controller that the call has been accepted. If the conduit is not adequate for extra wiring, plans for installation may require conduit and wiring replacement.

Some APS manufactured abroad initially required 110 volt AC power to the pushbutton rather than DC power. These manufacturers now supply APS models to the US market that are adapted to provide DC power to the pushbutton. It may be necessary to specify that devices meet US requirements.

Traffic signal controllers
APS devices work with current controllers used in the US. In the past year, some controller conflicts have been reported, mainly related to a change in voltage that leads to the MMU override. These have been addressed by the manufacturers and seem to be solved.

The Access Board has funded a project to investigate problems. Many issues reported seem to be incorrect installation or sound adjustment problems. The final project report should be available in 2003.

Developing technology
Two manufacturers are developing APS that can be adjusted by engineering staff using pocket computers or PDA type devices. These involve simpler wiring, and post-installation adjustment can be done from the sidewalk, with no need to open the APS, pedhead, or controller.

Controller board mounted behind 18 inch pedestrian signal head.
External mount for controller board is visible on the left side of the pedestrian signal head.
Mounting APS controller boards
Some APS have a controller board that is completely contained within the device. Other pushbutton-integrated APS require a separate controller board that is mounted in the pedhead. The controller board often includes voice or sound chips and switches to control volume, microphone response and other features.

Some types of pedheads do not have adequate space to mount the APS controller boards required by some types of pushbutton integrated devices:
  • Incandescent, 12 inch over/under pedheads may require replacement. Manufacturers generally can supply a separate box for the APS controller, if needed.
  • APS controller boards can be mounted in the controller. However, the correct gauge wires must be calculated to drive the speakers when wiring is extended across the street/intersection. Wiring that is adequate to drive the speakers when run from the pedhead to the pushbutton is not adequate to allow the full range of volume when run for longer distances, such as across the intersection.
topup arrow

  << previous page  |  next page >>
spacer image
This site was developed under the sponsorship of the National Cooperative Highway Research Program.