Intersection Geometry Considerations
Effect on APS
An APS that is audible from the wrong crossing location may lead a visually impaired pedestrian to begin to cross at the incorrect time and place. Geometric features, such as unsignalized and signalized right turn lanes, have been recognized as situations of concern in language in the MUTCD.
The type of APS may not be as important as the location of the sound source and volume of the WALK indication. These issues must be considered in the design phase in determining type of device and location. Also, careful adjustment of APS volume after installation is essential.
Unsignalized right turn lanes and splitter islands
Figure 6-5. APS at channelized turn lane
An unsignalized right turn lane can pose a problem if the APS for crossing the signalized main through lanes of the intersection is too loud. Pedestrians who are unaware of the existence of an unsignalized right turn lane may reach the curb, hear the APS sounding and cross the unsignalized lane, thinking that it is signalized.
This concern is the reason that Paragraph 11 of Section 4E.11 of the MUTCD urges careful adjustment of sound levels at locations with unsignalized right turns. Volume of the sound and placement of the speaker are the important issues.
The APS must be adjusted so it is only heard from the location where the pedestrian is waiting to cross and only audible for the crosswalk being signaled. It is generally not appropriate to use audible beaconing where there are splitter islands because the volume cannot be controlled precisely enough. As discussed in the section on split phasing, volume and placement of the sound source are critical considerations in designing and installing the APS.
In Figure 6-5, a pedestrian standing on the corner at location A should not be able to easily hear the APS that is located on the splitter island and for use by pedestrians crossing the through lanes.
Signalized channelized right turn lanes
Where crosswalks from corners to splitter islands are signalized, the signals to cross to the island might not be concurrent with traffic movement parallel to the pedestrian who is blind, depending on the crossing location. APS should be located precisely next to the associated crosswalks with careful volume adjustment. Pedestrians waiting on the island must not confuse the WALK indication for the turn lane with the WALK indication for the through lanes of the intersection. Pedestrians approaching the corner can also be guided to the crosswalk by a locator tone in combination with curb ramp location. Because signalized right turn lanes can be confusing for pedestrians who are blind, installation of APS with pushbutton locator tones at signalized right turn lanes should be given high priority.
Medians
Figure 6-6. APS at median midblock crossing
If the pedestrian clearance time is sufficient only to cross to a median having an additional pushbutton, it is very important that the pushbutton on that median be an APS with a locator tone. This may inform the pedestrian who is visually impaired that a second button press is needed to complete the crossing, and will aid in location of the median and the pushbutton. If only one APS device is on the median, the pushbutton should have a double-ended arrow.
If pedestrian phases for the two halves of the street are timed separately, two pushbutton-integrated APS are needed on the median, separated by as much distance as possible, and located as close to each crossing departure location as possible. Paragraph 4 of Section 4E.10 of the MUTCD requires an additional APS where clearance time is only sufficient to cross from the curb to the median. In addition to the locator tone of an APS, a fence and offset crosswalks are used in European and Australian cities to alert all pedestrians about the need to stop on the median and wait for the next pedestrian phase.
At this median island in Ireland (Figure 6-6), an APS is provided for each crossing, and a fence prevents pedestrians from continuing straight across the street, requiring the pedestrian to turn and walk to the other crosswalk location and pushbutton.
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