Much of this section comes from a publication of the Environmental Access Committee of the O&M Division of AER (Association for Education and Rehabilitation of the Blind and Visually Impaired).
For detailed information on APS and installation, see www.apsguide.org.
What is an Accessible Pedestrian Signal?
Photo of pushbutton-integrated APS
The Manual on Uniform Traffic Control Devices (MUTCD) defines an Accessible Pedestrian Signal as "a device that communicates information about pedestrian timing in nonvisual format such as audible tones, verbal messages, and/or vibrating surfaces." (Manual on Uniform Traffic Control Devices 2009, Section 1A.13, paragraph 3)
Why are they needed?
Changes in intersection design and signalization, as well as the presence of quiet cars, have affected the traditional street crossing techniques used by pedestrians who are blind or visually impaired, making the pedestrian phase harder to recognize without seeing the visual pedestrian signal. At many intersections, the pedestrian phase (the time during which pedestrians are allowed to cross) does not correspond with the green signal for the vehicles, for example where vehicles are allowed to turn left while pedestrians wait, and at leading pedestrian intervals (which give the pedestrians a head start) and exclusive pedestrian phasing (which allow pedestrians to cross but all vehicles have a red signal). Some locations require pedestrians to push a button to actually receive enough time to walk across the street. Pedestrians who cross without pushing the button are likely to still be in the intersection when perpendicular traffic begins moving.
In many states in the U.S., it is illegal to begin crossing during the flashing don't walk or don't walk intervals of the pedestrian signal.
APS provide the same information that is provided by the visual pedestrian signal to sighted pedestrians in an audible and vibrotactile format, making it possible for pedestrians who are blind to precisely identify the onset of the WALK signal.
Accessible Pedestrian Signal Features
The 2009 MUTCD specifies that all newly installed APS have the features listed below.
These types of APS provide sounds from the pedestrian pushbutton housing, rather than from overhead speakers.
They are sometimes called pushbutton-integrated APS, and have been common in Europe and Australia for years.
APS features required as standard are:
an audible walk indication
The sound to indicate the walk interval may be a rapid ticking tone, or a speech message. Which type of sound is used is determined by the location of the two APS on the corner.
a vibrotactile walk indication
The walk interval is also indicated with a vibration of the pedestrian pushbutton or other parts of the pushbutton housing, so that pedestrians who are deaf-blind can access it.
a pushbutton locator tone
A quiet locator tone, repeating once per second during the flashing and steady don't walk signals, provides information to blind pedestrians about the presence and location of a pedestrian pushbutton. The locator tone should be adjusted to be audible 2 to 4 meters (6 to 12 feet) from the pole or from the building line, whichever is less.
a tactile arrow
The tactile arrow indicates which crosswalk the pushbutton is for. It should be aligned with the direction of travel on the crosswalk it controls, which means that it should be parallel to the crosswalk, rather than pointing to the crosswalk itself.
automatic volume adjustment
This type of APS automatically adjusts the volume of its locator tone and audible WALK indication in response to ambient sound levels. The signals are intended to be loud enough to be heard ONLY at the beginning of the crosswalk, but on some APS, volume is increased for the next pedestrian phase if pedestrians press the pushbutton for one second or longer.
It is important to note that some jurisdictions are installing APS that require pedestrians to press the pushbutton for at least one second to get the audible walk indication. This policy should be discouraged, as pedestrians shouldn't have to "know the code" in order to get access to the walk signal.
Special features available on request with some APS
Some APS provide extra features when you hold the pushbutton down steadily for a few seconds.
These features may include:
verbal information about the crossing;
an increase in the volume of the audible signal for that crossing during the next pedestrian phase;
a longer crossing time, if it is feasible at that intersection.
Many APS manufacturers provide these features as standard in their products.
Engineers can implement them at any time after installation, and are often willing to do so if they are requested.
Installation in the proper location and orientation in relation to the crosswalk is important for the use of any type of APS.
The MUTCD, based on recent research, recommends that each APS device should be on a separate pole, located as close as possible to the curb line, and as close as possible to the crosswalk line that is furthest from the center of the intersection.
The recommended WALK indication for APS that are located according to these recommendations is a fast tick, or percussive sound, at 10 repetitions per second.
Two APS on a corner should be at least 10 feet apart in order for pedestrians to easily distinguish which device is sounding.
Both APS should have the same WALK indication; the direction of the sound source clarifies which crosswalk each APS signals.
Obviously, in retrofit situations, this wouldn't be possible in all cases, however, this is the installation goal, and clients/students need to know about the APS installation guidelines for new locations.
When pushbuttons are precisely and consistently located in this way, identification of which crossing is being signaled can be based solely on which pushbutton the WALK signal comes from.
There is no need to remember a code (such as cuckoo for a north/south crossing and rapid tick for an east/west crossing) or to understand speech messages.
The drawing on the right shows ideal APS installation locations on a corner.
A ramp leads to each crosswalk, and each pushbutton is near the top of the ramp on the side of the crosswalk furthest from the parallel street.
Below the drawing is a photo showing an APS in San Francisco.
It was installed correctly, with the APS on a pole near the street, in line with the crosswalk line.
For examples of pole arrangements that meet the requirements for corners having different geometries with various typical curb ramps, see APS: Guide to Best Practice.
What if ideal placement cannot be achieved?
Where it is technically infeasible to install two APS pushbuttons (and speakers) on a corner on two separate poles at least 10 feet apart, it is recommended that speech WALK messages be used.
The required wording is "[street name] walk sign is on to cross [street name]", for example, "Beechwood; walk sign is on to cross Beechwood".
If speech walk messages are used, it's essential that pedestrians know the name of the street being crossed.
An additional feature, called a pushbutton information message, is needed on the device to provide street name to pedestrians who are unfamiliar with the intersection.
If the pushbutton is pushed in and held for more than one second, the name of the street controlled by the pushbutton is stated.
Adjustment of APS
Proper placement of the APS and careful adjustment of the APS volume can be critical, both for usability by pedestrians who are blind and for neighborhood acceptance.
The pushbutton locator tone and walk indication are normally supposed to only be audible 6 to 12 feet from the pushbutton.
Your students and you should be encouraged to contact the traffic engineers responsible for that intersection
if the APS or pushbutton is not functioning as it should.
It may also be possible for the engineer to add some of the special APS features that are explained above.
In the U.S., the first and best course of action for requesting an APS is to draft a letter with your student/client following the process developed by the Environmental Access Committee of AER's Orientation and Mobility Division.
Secondly, it can be useful to become connected with the Planning and Engineering folks in your area through Advisory Committees or Community Outreach Meetings. These connections can keep you in the loop about ongoing projects so you can provide information about APS (and other access issues) in the planning stages when budgeting is less of an issue.