Research on other APS Features

Previously described research has also looked at other specific features of APS including the pushbutton locator tone. The following sources are referred to: NCHRP 3-62 research, Barlow et al. 2005 and Bentzen et al., in press; Poulsen, 1982; San Diego research; and Williams et al., 2005.

Pushbutton locator tones

Pushbutton locator tones are a standard feature of almost all pushbutton-integrated APS in use worldwide. In the U.S. they are standardized to repeat once per second, and are to be audible only 6-12 feet from the pushbutton unless there is special actuation to raise the volume during the following pedestrian phase (Manual on Uniform Traffic Control Devices 2003 4E.09; Guidelines for Accessible Public Rights-of-Way, revised 2005) . Pushbutton locator tones inform blind pedestrians that they need to push a button to actuate a WALK signal and/or pedestrian timing. Because the sound comes from the pushbutton, it indicates the location of the pushbutton.

Bentzen, Barlow, & Gubbé (2000), compared the speed of blind pedestrians on locating and walking to an APS with a pushbutton locator tone (880 Hz square wave, with multiple harmonics, 3 ms attack time, 15 ms sustained tone) at three repetition rates and three loudness levels relative to traffic sound along an eight lane artery in Los Angeles. Best performance was with a repetition rate of once per second and loudness of 2–5 dBA above ambient sound measured at 1 meter from the locator tone speaker.

Tactile arrow

Tactile arrows aligned in the direction of travel on the associated crosswalk are features of all known pushbutton-integrated APS in use worldwide. Arrows vary in size and location on the APS. Some are on the pushbutton, some are on the vertical face of the housing and some are on the top (horizontal) surface. The length of the arrow varies from approximately 1.5 inches to 2.5 inches; stroke thickness varies from approximately 3/32 inch to ¼ inch; and height above the surface varies from approximately 1/6; inch to ¼ inch.

The only research on usefulness of the tactile arrow for establishing crossing alignment was done in Denmark by Poulsen (1982). The "arrow" tested was a rod on top of the APS that was approximately 2.5 inches in length, ¼ inch in width, and ¼ inch high, with a bump indicating the far side of the crossing and additional bumps indicating the presence of islands or medians, if any. Alignment was equal with or without use of the arrow. The size and graspability of this unique arrow, as well as its location on the top of the APS, are thought to make it a better indicator of direction than smaller, non-graspable, arrows and those mounted on the vertical face of the APS. The failure to find any positive effect on alignment indicates that such an arrow (or probably any arrow) should not be considered a primary cue for alignment.

Nonetheless, tactile arrows do serve the important purpose of indicating the crosswalk with which a particular APS is is associated. Research under NCHRP 3-62 (See Final Report and Bentzen et al. in press) found that increased familiarity with tactile arrows in Tucson and Charlotte resulted in an increase in use of tactile arrows, with arrows actually on the pushbutton being used more frequently than arrows that were not on the pushbutton itself. While participants looked at the incorrect (not desired crossing) arrows on 28 trials in Tucson, after extensive familiarization, they then found and pushed the correct pushbutton on all of these trials. In Charlotte, while there was a decrease in use of the wrong pushbutton following extensive familiarization, use of the wrong pushbutton on some trials remained. Under the same research, subjective responses indicating preference for various features indicated strong support for use of a tactile arrow to identify the correct pushbutton.

Vibrotactile indications

Most pushbutton-integrated APS worldwide have vibrating tactile arrows or other surfaces that vibrate during the WALK interval. The vibration is required by pedestrians who are deaf-blind to inform them that the WALK signal is on. It is also used by some pedestrians without hearing loss to confirm which crosswalk has the WALK signal, especially in very noisy conditions.

Because it is necessary for pedestrians who are deaf-blind, as well as helpful for blind pedestrians in some situations, a vibrotactile WALK indication is required along with an audible WALK indication in the Draft Guidelines for Accessible Public Rights-of-Way. A signal having vibrotactile indication only is not permitted. An APS that is vibratory only gives no indication of whether there is a pushbutton, or where the pushbutton is located, and it gives no audible directional guidance.

Gallagher and Montes de Oca (1998) surveyed blind pedestrians who were familiar with vibrotactile signals that did not have audible WALK indications, and on which a vibrating arrow was located on a horizontal surface above the pushbutton. They found the vibrotactile signal to be well-liked. In field research, they also found that use of the vibrotactile indication resulted in accurate crossing timing.

Tactile Map of the crosswalk

Maps of the crosswalk are standard features of pushbutton-integrated APS in Sweden, are in wide use around the world where Swedish devices are used, and are required in Austria for all APS regardless of the equipment manufacturer (see Chapter 4 for photos and more information]. There does not appear to be any research on the legibility or effectiveness of these maps of the crosswalk, but they do have the potential to enable users who are unfamiliar with a particular crosswalk to anticipate such characteristics as the number of vehicular lanes in each direction, and the presence of islands or medians, rail tracks, and bicycle lanes.

In NCHRP 3-62 research (see and Bentzen et al., in press) one of four devices compared had a tactile map of the crosswalk. Mean ratings of participant agreement in Tucson and Charlotte to the statement "The crossing map was useful and easy to understand," were 4.00 and 4.17, re4spectively, on a 5-point scale (5 = strongly agree). However, even when they were thoroughly familiar with the map, only 9 of 40 participants used it across the two cities.

Pushbutton information message

On some pushbutton-integrated APS, an optional feature is a speech message that comes from the pushbutton either whenever the button is pushed, or whenever the button is pushed and held in for an extended time (see Extended Button Press, above). This message always begins with the word "Wait", as it comes on only during the flashing and steady DONT WALK intervals. The next information identifies the intersection and the street to be crossed. The recommended format for this message is "Wait, to cross Howard at Grand." Additional information may be provided regarding unusual signalization (e.g. split phasing) or geometry (e.g. narrow median in the roadway).

In research conducted under NCHRP 3-62 (NCHRP 3-62 Final Report, Chapter 3; Bentzen et al., in press), three of four devices used in field research in Tucson and Charlotte had pushbutton information messages. On all three devices, the pushbutton had to be depressed for at least three seconds to actuate the full pushbutton information message. One device did not have the standard pushbutton information message when used in Tucson. The objective measure most closely related to the pushbutton information message was only whether participants used the extended button press which actuated the pushbutton information message; it was not possible to observe whether participants actually understood or used the information provided by the pushbutton information message. However, when asked to rate the extent of their agreement with the statement "The pushbutton information message was easy to understand," the mean ratings for each city were above 4.0 on a 5-point scale (5 = strongly agree), indicating that the message was usually understood.

Extended button press

Additional features on pushbutton-integrated APS may be actuated by an extended button press. These features include a pushbutton information message, a louder (beaconing) signal, and extended crossing time.

Noyce and Bentzen (2005) found that it was unusual for pedestrians to push pushbuttons for as long as one second. Therefore an extended button-press of only one second is being standardized to actuate any optional features that are available at an APS.

In NCHRP 3-62 research (NCHRP 3-62, Final Report, Chapter 3; Bentzen et al, in press) the extended button press feature was included on three of four types of APS. The extended button press was little used except following familiarization with each device. The extended button press was used on 65-85% of crossings in Tucson and Charlotte following familiarization to device features. This may indicate that specific information and training are necessary for pedestrians who are blind, if use of the extended button press is expected. Desirability of a pushbutton information message as well as beaconing, both of which were actuated by an extended button press, was supported by subjective data.

Audible beaconing

An optional feature on some currently available APS is audible beaconing, which is usually actuated only by an extended button press. Beaconing is provided by a louder signal during the next pedestrian phase. The beacon is intended to aid initial alignment for crossing and crossing within the crosswalk.

In NCHRP 3-62 research (NCHRP 3-62 Final Report, Chapter 3; Bentzen et al, in press), one of four devices tested had the audible beaconing feature. On this device, the WALK signal and subsequent locator tone increased in volume for the next pedestrian phase following a button press of at least three seconds. No objective measure of the use of audible beaconing could be made. The only measure possible was use of the extended button press feature that also actuated a pushbutton information message. However, when asked to rate the extent of their agreement with the statement "The louder signal was helpful," the mean responses for Tucson and Charlotte were 3.86 and 4.00, respectively, on a 5-point scale (5 = strongly agree), indicating that this feature is desirable.

Additional research on the usefulness of APS for alignment and crossing within the crosswalk is provided under Effect of APS on specific crossing tasks: Results of research: Orientation, above.

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