Mounting and Wiring Issues
Location of controller boards and wiring
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. However, some manufacturers now provide devices that can replace typical pushbuttons and require only two wires and an additional control unit in the controller cabinet.
Some APS manufactured abroad initially required 110 volt AC power to the push button rather than DC power. These manufacturers now supply APS models to the U.S. market that are adapted to provide DC power to the pushbutton. It may be necessary to specify that devices meet U.S. requirements.
Traffic signal controllers
APS devices work with current controllers used in the U.S. In installations from 2000–2003, some controller conflicts were reported, mainly related to a change in voltage that leads to the Malfunction Management Unit (MMU) override. These have been addressed by the manufacturers and seem to be resolved. In 2002, the Access Board funded a project to investigate problems that found that many issues that had been reported were due to incorrect installation or sound adjustment problems. The final project report is available on the access board website at www.access-board.gov.
Mounting APS controller boards
Some APS have a control board that is completely contained within the device. Other APS require a separate control board that is mounted in the pedhead (see Figure 6-18), while still others require a control unit mounted in the controller cabinet. The control 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 APS control boards. For example, incandescent, 12 inch over/under pedheads may not have adequate space. These pedestrian signal heads can be replaced. Other options may include:
- Manufacturers may be able to supply a separate case for the APS control board (see Figure 6-19).
- APS control boards may be mounted in the signal controller. However, the correct gauge wires must be calculated to drive the speakers when wiring is extended across the street/intersection. Included wiring is usually only adequate to drive the speakers when run from the pedhead.
If an area typically experiences high winds, it may be necessary to mount the APS speaker on a strong surface. Engineers in Nova Scotia found that speakers mounted on the plastic pedhead were prone to cracking off during times of high wind. Their solution was to mount the speakers directly to the metal pole, as shown in Figure 6-21.
Figure 6-18. APS device with control board in pedhead (speaker opened for illustration)
Figure 6-19. External mount for controller board is visible on the left side of the pedestrian signal head
Figure 6-20. Controller Board mounted behind 18 inch pedestrian signal head
Figure 6-21. APS speaker mounted directly to the metal pole for more support during high wind
Vibration-only devices are not recommended. However, pushbutton-integrated APS should have a vibrotactile arrow that vibrates during the WALK interval. The vibrotactile arrow can be useful in confirming the audible WALK indication and providing WALK signal information to individuals with impaired hearing. Designers/engineers and installers must remember that the vibrating surface will be usable only if they are installed within the width of the crosswalk or very near the crosswalk, and near the curb line. Pedestrians must be in an appropriate position to begin their crossing while waiting with their hand on the vibrating surface.
Orientation of tactile arrow
The tactile arrow must be oriented parallel to the direction of travel on the crosswalk controlled by the pushbutton. Arrows on several manufacturers' devices are positioned by the installer; however, with some devices, the direction of arrow is specified when ordering the units. The pole location in relation to the crosswalk can affect the direction of the arrow.
Figure 6-22. The direction of the cast-in-place arrow on this device must be specified when ordering
In areas where pushbuttons are installed on wooden poles, the wiring usually runs within a conduit on the outside of the pole. A mounting bracket is needed on some devices for wiring the pushbutton. This bracket needs to be ordered with the APS.
Pedestrians who are blind have expressed concerns about nails and staples that are common on wooden poles and which present a hazard for their hands when locating the button (see Figure 6-26). Innovative solutions include the use of a shield for the pole area near the pushbutton to solve this problem, as shown in Figure 6-27.
Figure 6-23. Mounted on a wooden pole, an additional mounting bracket is installed to allow the wires to run from the conduit into the top of the pushbutton-integrated device.
Figure 6-24. Typical installation without extra mounting plate, with wire running from inside the metal pole into the back of the device
Figure 6-25. This APS is mounted on a wooden pole by drilling a hole through the pole and running wires through the back of the device
Figure 6-26. Wooden pole with nails and staples that are typical and a source of concern
Figure 6-27. Coated canvas shield used in Charlotte, NC
The use of stub poles for mounting pedestrian pushbuttons is common in some areas of the U.S. They provide an opportunity to locate the pushbutton where it is most usable to pedestrians and may improve pedestrian compliance with pushbutton use.
Figure 6-28. A stub pole is used to locate the pushbutton beside the sidewalk
Figure 6-29. Stub pole example
Figure 6-30. Stub pole installed near sidewalk signal box simplifies wiring and locates ped pushbutton by the crosswalk
Figure 6-31. Stub pole example
Braille labels and signs
Before ordering APS with Braille labels on the faceplate, you must know:
- The location of the pole, and
- Which side of the pole the APS will be mounted on
The direction of the face plate and associated arrow is determined when the raised dots of Braille are added. Braille is generally just punched into the metal plate.
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