Interfacing Accessible Pedestrian Signals (APS)
 with Traffic Signal Control Equipment [PDF File]

 

David A. Noyce, Ph.D., P.E.

University of Wisconsin – Madison

University of Massachusetts – Amherst

 

Janet M. Barlow, C.O.M.S.

Certified Orientation and Mobility Specialist

Atlanta, GA

 

April  2003

 Pedestrian with guide dog at intersection with audible pedestrian signal.


TABLE OF CONTENTS

ABSTRACT
INTRODUCTION
RESEARCH OBJECTIVES
TRAFFIC SIGNAL CONTROLLERS
ACCESSIBLE PEDESTRIAN SIGNAL (APS) TECHNOLOGIES
INTERFACING APS DEVICES WITH TRAFFIC SIGNAL CONTROL EQUIPMENT
LESSONS LEARNED FROM EXISTING INSTALLATIONS
APS PRODUCTS AND MANUFACTURER INFORMATION
APS MANUFACTURER CONTACT INFORMATION
APPENDIX A - TRAFFIC SIGNAL CONTROLLERS
APPENDIX B - REFERENCES

ABSTRACT
 
The primary objective of this research was to provide detailed accessible pedestrian signal (APS) product information specifically focused on the interfacing of APS devices and traffic signal controllers.  Information on the various traffic signal controllers used today is also provided.  The information is intended for traffic engineers, traffic signal technicians, and others who are implementing APS technologies. 

This report addresses the following information:
  • United States and foreign APS technologies, including those that provide mapping, speech, and location features for blind pedestrians;
  • Traffic signal controller/APS interfaces, including wiring and power requirements and interaction with conflict monitoring technology;
  • Lessons learned from existing installations; and
  • United States traffic signal controller technologies.

Contact information for APS and traffic signal controller manufacturers is provided.  Funding for this research was provided by the U.S. Access Board.  The authors would like to thank Joseph Herr, VHB; Billie Louise Bentzen, Accessible Design for the Blind; Paul Vetter, Edwards and Kelcey; and David Grilley, City of Portland, OR for providing information used in this report and for their thorough, thoughtful, and timely review of the draft manuscript.  Their comments and suggestions led to many important improvements in content and description.

INTRODUCTION

The Millennium Edition of the Manual on Uniform Traffic Control Devices was the first to incorporate standards for accessible pedestrian signals (APS) (1).  APS is defined as a device that communicates information about pedestrian timing in a non-visual format such as audible tones, verbal messages, and/or vibrating surfaces.  Chapter 4E of the MUTCD, “Pedestrian Control Features” includes criteria for the implementation of APS devices into existing traffic signal systems.  Information is provided on audible tones and verbal messages, vibrotactile features, pedestrian detectors, and pushbutton locations.  A task group of the Signals Technical Committee and National Committee on Uniform Traffic Control Devices (NCUTCD) led the development of the new provisions.


Several companies, located in the United States, Europe, and Australia, manufacture APS products that provide information in non-visual formats.  Newer technologies provide speech, location, and mapping features at the push button; these devices have different installation requirements than the cuckoo/chirp pedhead-mounted speakers familiar to many United States traffic engineers.  New APS devices are ambient sound responsive and may have tactile arrows, mapping, and speech information and location features that require different sound adjustment, wiring, and installation considerations.


APS devices that make information about the status of signal phases available to visually impaired pedestrians can provide significant benefits in usability, safety, and independence (2, 3).  Nevertheless, the recent influx of new APS products has led to some confusion concerning installation criteria and compatibility with current U.S. traffic signal controller equipment.  Additionally, several transportation agencies that have recently installed one or more of the APS devices have reported minor problems in their installation and operation; most have proved to be easily correctable. 


Concerns with the installation of APS devices have included:

  • The high voltage to the push button provided by some APS devices,
  • Confusion over wiring requirements,
  • Installation of two APS devices on the same pole confusing the vibrotactile information for each walk intervals,
  • Controller conflicts which allow the APS to continue to provide WALK information when the traffic signal is in the flashing mode, and
  • Installations that prevent the traffic conflict monitors (malfunction management units - MMU) from detecting errors in pedestrian information presentation or that send the traffic signals into flash due to voltage variations detected by the conflict monitor. 
Although the APS devices in each case were installed with the best of intentions, installation deficiencies can create a real safety concern for the blind pedestrian and frustration for the traffic engineers and professionals responsible for the traffic signal system.  Traffic professionals, and those who install APS devices, need to be knowledgeable on the product features and installation requirements to assure that all appropriate features are included and operate correctly.    

 


RESEARCH OBJECTIVES


The primary objective of this research was to provide specifiers and installers with the information needed for problem-free operation of APS devices.  To fulfill this objective, detailed APS and traffic signal controller product information is provided, specifically focused on the interfacing of APS devices and traffic signal controllers.  Information includes:

  • Lessons learned from existing installations;
  • A detailed description of available APS technologies that provide mapping, speech, and/or location features for blind pedestrians;
  • Detailed information on how the APS devices interface with each traffic signal controller including:
- Wiring requirements;

- Power requirements;

- Interaction with conflict monitoring technology;
  • A detailed description of traffic signal controllers (and manufacturers) currently used in the U.S. and those that may be available in the near future.

The following sections provide a description of each of the above items.
 

 

TRAFFIC SIGNAL CONTROLLERS


Control of vehicle and pedestrian movements in the U.S. via traffic signals has been in place for over 100 years.  The earliest traffic signals were manually operated, requiring a police officer or city employee to manually “switch” traffic flow by changing red and green panels or lights in a switch stand.  As traffic continued to grow, it became obvious that mechanical/electrical signal controllers were required to relieve police officers of their traffic control duties. 


Electrically operated traffic signals have been in operation in the U.S. since 1914.  Electric traffic lights were first installed in Cleveland, Ohio, at Euclid Ave. and 105th Street (4).  The traffic signal consisted of two long cross-arms, red and green lights, and buzzers.  Two long buzzes signaled Euclid Avenue traffic to proceed, one long buzz meant it was 105th Street's turn to go.  Note that this signal had both a visual and audio component.


Since then, traffic signal control equipment has undergone continual improvement. The earliest signal controllers used motors and gears to time the durations of the signal indications; some of these controllers can still be found in use.  Technology and the computer era have brought microprocessor-based signal control equipment to what we have today, a complex yet functional system of automated control located at more than 300,000 intersections.
 

Current Controller Standards

Two standards are used today for traffic signal controllers (5, 6).  The National Electrical Manufacturers Association (NEMA) developed one controller standard.  Two generations of the NEMA standard are used today, namely the TS 1 (1976) and the TS 2 (1992).  The TS 2 is further divided into Type 1 and Type 2 controllers.  A second standard was developed by the California Department of Transportation (Caltrans) and the New York Department of Transportation (NYDOT).  The original standard was developed under the Type 170 platform in 1979.  Updated platforms have included the Type 179, Type 170E, and Type 2070. 


Detailed information about these standards and controller features is provided in Appendix A of this document.
 

 

ACCESSIBLE PEDESTRIAN SIGNAL (APS) TECHNOLOGIES


Accessible pedestrian signals (APS) are enhancements to the traffic signal system to provide signal phase information in audio, tactile, and/or vibrotactile formats for the pedestrian.  APS devices available today are of four general types: pedhead mounted, pushbutton integrated, vibrotactile only, and receiver-based.


Pedhead-mounted APS are the only type that have been commonly installed in the U.S. for the past 25 years.  This type has a speaker on top of or inside the pedhead with a bell, buzzer, cheep, cuckoo, speech message, or some other tone during the walk phase of the signal only.  Some models respond to ambient sound, becoming louder when the traffic noises are louder and quieter when the traffic is quiet.  They are usually intended to be heard across the street and act as a beacon, and are relatively loud as a consequence.  Manufacturers include Mallory, Novax, US Traffic, and Wilcox.  Prisma and Campbell also have an optional additional pedhead mounted speaker that can be used in conjunction with their pushbutton integrated device.


Pushbutton-integrated APS have a speaker and a vibrating surface or arrow at the pedestrian button.  The sound comes from the pedestrian pushbutton housing, rather than the pedhead.  This type has been common in Europe and Australia for years and can be used at both actuated and fixed-time signal timing locations. A constant quiet locator tone, repeating once per second, provides information to the blind individual about the presence of a pedestrian pushbutton and its location.  The locator tone is intended to be audible only 2 to 4 meters (6 to 12 feet) from the pole or from the building line, whichever is less. 


The walk interval may be indicated by the same tone at a faster repetition rate (Panich, Prisma), by a speech message (Polara, Campbell, Novax, Prisma), or by other tones (Campbell, Polara, Novax).  All devices of this type respond to ambient sound levels.  These signals are intended to be loud enough to be heard only at the beginning of the crosswalk, although volume can be increased by special activation (Polara, Prisma, Campbell).  Manufacturers include Campbell, Georgetown Electric (locator tone not ambient sound responsive), Novax (locator tone and vibrotactile arrow combined with pedhead speaker), Panich, Polara, and Prisma.


Vibrotactile-only APS provide only vibration at the pedestrian pushbutton. The arrow or button vibrates when the WALK signal is on.  It must be installed very precisely next to the crosswalk to be of value, and the pedestrian must know where to look for it.  Manufacturers include Campbell and Georgetown Electric.


Receiver-based APS provide a message transmitted by infrared or LED technology from the pedhead to a personal receiver.  The pedestrian scans the intersection with the receiver to receive the message emitted on the pedhead.  These devices may also give other types of information, including information about the name of the streets or the shape of the intersection.  Manufacturers include Relume and Talking Signs.


The section on APS devices provides details of each of the APS devices available at the time of this report.  Information was obtained from phone, e-mail, Internet, and mail contacts with manufacturers and from the draft report, Accessible Pedestrian Signals: Synthesis and Guide to Best Practice by Accessible Design for the Blind [www.accessforblind.org], being prepared as part of NCHRP Project 3-62: Guidelines for Accessible Pedestrians Signals (7). A matrix summarizing features provided by each device is also included.
 

Information about APS devices produced by the following manufacturers is included in this publication:

  • Campbell Company
  • Georgetown Electric, Ltd.
  • Mallory Sonalert
  • Novax Industries Corporation
  • Bob Panich Consultancy
  • Polara Engineering
  • Prisma Teknik
  • Relume
  • Talking Signs, Inc.
  • U.S. Traffic Corporation
  • Wilcox Sales

For more information on intersection design to accommodate APS, consult the references and associated web sites.
 


 

INTERFACING APS DEVICES WITH TRAFFIC SIGNAL CONTROL EQUIPMENT


APS devices work with existing traffic signal controller logic to provide the desired information to the pedestrian.  Most APS devices require no additions or activity within the traffic signal controller cabinet for installation and operation.  APS devices are designed to work with either the green, red, WALK, or DON’T WALK indications, and to coordinate calls with the pedestrian pushbutton.  Therefore, existing wiring from the traffic signal controller to the pedestrian signal heads and pushbuttons is maintained and unaltered.  There is nothing done to the traffic signal controller during the installation of an APS device.  In most cases, the only way a traffic controller system knows that an APS device is present is if voltage problems in the APS unit are detected by the controller’s conflict monitor.


In most cases, the APS device is driven by the pedestrian signal head (pedhead) indications.  When electrical power is sent to the pedhead to illuminate the WALK indication, the APS device is also activated.  All units currently available are wired in some way to the pedestrian signal wiring.


APS devices that are pedhead-mounted provide sound only during the walk interval. These devices are typically wired directly to the WALK indication, without other features or issues. 


APS devices that are pushbutton integrated have additional control units that may be installed (depending on the manufacturer and the device) in the pedestrian signal head (16” clamshell style, typical) or contained completely within the pushbutton unit.  At least one manufacturer also provides control units that can be installed in the traffic controller cabinet in lieu of the pedhead.  Some provide a separate housing that must be mounted on the signal pole.  Control units control operation of the locator tone, pushbutton messages and other features available on the pushbutton integrated devices. Pushbutton-integrated devices can also function at pretimed intersections, without pushbutton operation.

Receiver-based devices vary depending on the type of signal.  Some include a control unit mounted in the pedhead will others include a replacement pedhead that is installed and wired as a regular pedhead.

Wiring and Power Requirements 

The control units for integrated APS devices require additional wiring, most often from the pedhead to the pushbutton.  Wiring requirements are quite similar with each mounting strategy.  Power requirements are consistent with the traffic signal controller, pedhead, and pushbutton specifications directed by NEMA.  APS control units in the pedhead usually convert the 120 VAC to a lower voltage (24 VDC) to the pushbutton.  Specific wiring and power requirements are described with each APS device later in this report.

 

Interaction with MMUs and Conflict Monitors

The MMU, or conflict monitor, performs several functions, the most important of which is to prevent two conflicting green indications from being illuminated.  The conflict monitor is really a voltage monitor, looking for inappropriate voltages in inappropriate locations or voltages that are above or below desired levels.  The conflict monitor will track multiple components, including the cabinet field wiring terminals for voltage on conflicting signal indications and cabinet voltage to assure that the proper operating range is maintained.


APS devices do not directly interact with the conflict monitor, outside of the fact that the voltage requirements and outputs from the APS units will be monitored within the system specifications.  Problems with APS devices can develop when the voltage outputs exceed current conflict monitor limits.  When this happens, the conflict monitor overrides the signal control system and places the signal into flash mode.  Other problems exist when additional wiring is added from the pedhead to the pushbutton that creates a separate circuit that is no longer detectable by the conflict monitor.  Some discussion of this problem is included in the troubleshooting described in the next section, “Lessons Learned from Existing Installations.”


 


LESSONS LEARNED FROM EXISTING INSTALLATIONS


Interfacing new APS devices with modern traffic signal control systems is not as problematic as industry initially believed.  Most APS devices do not interface with traffic signal controllers at all, and those that do only provide equipment inside the cabinet.  Problems experienced to date have been minor and correctable; issues presented are not dissimilar to any device associated with traffic signal systems.  Many of the problems seem related to a lack of understanding by installers, who may not yet be familiar with the new types of devices, wiring, and the use of the various features.  Pushbutton-integrated devices require additional wiring between the pedhead and pushbutton, more attention to pushbutton placement and alignment, and careful adjustment of sound volumes.  APS devices provide a real benefit to all pedestrian movements at a signalized intersection.  The information presented in this section can help those who use and/or install APS devices to avoid problems.


As with any new technology, the first installation of a new type of APS device may not always operate flawlessly.  However, most are easily solvable, either by manufacturers’ adjustments to their devices or by adjustments to the installation.  Key issues discussed here include:

  • APS compatibility with controller MMU/Conflict Monitor;
  • Wiring to pedhead and/or controller;
  • Pushbutton installation;
  • Signal phasing;
  • Speaker positioning and volume;
  • Pushbutton and pole location;
  • Tactile arrow location and position;
  • Use and proper wording of speech messages; and
  • Braille signage and correct installation.

 

APS/Conflict Monitor Compatibility

APS compatibility with the MMU/conflict monitor is related to voltage issues.  When unexpected voltages or voltages outside of a given range are detected, the MMU overrides the controller functions and places the signals into a flash mode until maintenance is performed.  Most problems in this area have been identified by installers; manufacturers have made modifications to prevent such problems in the future.


Some of the APS devices manufactured internationally were designed with different voltage standards – voltage ranges that differ from current U.S. specifications.  In reducing the voltage requirements to the pushbutton, another issue developed with one manufacturer.  Some equipment was designed to send 120 VAC to the pushbutton to provide the vibrating surface during WALK, when 24 VDC or less is desired in the US.  A circuit to reduce the voltage was successfully created, but the resultant circuit was external to the pedestrian wiring and therefore undetectable by the conflict monitor. In this installation, the conflict monitor would not override the conflicting pedestrian signals  nor would the signals be placed into a flash mode when a pedhead malfunction occurred.  The manufacturer has developed an alternative vibrating pushbutton that operates with appropriate voltage at the pushbutton and does not require an extra circuit.


 

Wiring Some problems have also been experienced with wiring and color code practices of devices manufactured abroad.  Some device manufacturers used European or Australian wire color practices and standards.  These practices are not consistent with what is commonly used in the U.S., resulting in some wiring confusion.  Although NEMA and the U.S. National Electrical Code (NEC) do not specifically define system wire color codes, many locations have developed color requirements and “rules-of-thumb.”  Some color codes that existed in years past have been eliminated for safety reasons assuring that technicians working with the signal wires don’t assume a wire function based on color alone.  Therefore, all wires should be tested to identify its use, regardless of color.  International companies have developed devices for U.S. installation but care should be taken to review the instructions and wiring of the devices to assure that devices are wired properly.  Installers should not assume the function of a wire by its color.


Some of the APS devices manufactured internationally were designed with different voltage standards – voltage ranges that differ from current U.S. specifications.  Particularly, foreign devices drew concern from signal technicians over the high voltage sent to the pushbutton location. Voltage to the pushbutton was originally 120 VAC, compared to 24 VDC typical in the U.S.  Technicians were concerned about pedestrian safety if the push button is damaged or the push button is taken off by a passing vehicle, and a pedestrian comes in contact with the live wires or electrically charged metal pole.  US models with transducers mounted in the pedestrian signal head have been developed.  The problem was resolved by placing transducers in the system to reduce the voltage from the pedhead to the pushbutton location.  Units with voltages common to U.S. installation are now being produced by all manufacturers listed in this report.


Some problems were initially found with the controller recognizing the pedestrian pushbutton actuation.  Most pushbutton units have been found to work well with both the NEMA and 170 controllers because both (along with the conflict monitors) are sensitive to electrical deficiencies.  APS devices may be more sensitive to electrical differences than a typical pushbutton.  A minor electrical short, not affecting a standard pedestrian push button, prevented an APS installation from working properly.  The electrical short was identified and removed using common diagnostic procedures.


 

Pushbutton Installation

Pushbuttons are often installed on the most adjacent pole to the intersection.  At times, two pushbuttons with vibrotactile outputs may be installed on the same metal pole.  Vibrotactile APS devices require insulation and a rubber gasket to eliminate vibrations generated from the other pushbutton.  Without vibratory insulation, pedestrians may not be able to determine which device has the WALK indication since both will vibrate.  Proper insulation of all pushbutton installations (or separate poles) will prevent this problem from occurring.


 

Phasing

A potential issue with wiring of APS devices is the conflict monitor interface, making sure the device communicates with the traffic signal system.  When traffic signals go into flash mode, the APS device must not remain in WALK mode.  This problem can be avoided by correctly wiring the APS device into the controller/signal system so the controller logic and conflict monitor can detect and change the pedheads to the appropriate indications. 


When a phase rests in WALK, either the WALK indication continues for several minutes at a time or a pushbutton is needed to start the tone, speech, and/or vibratory indications.  If continuous, the WALK sound can be irritating for neighbors, even at a quiet volume, so it may be preferable to have it begin in response to actuation in residential settings.  With semi-actuated phasing, a pushbutton is usually not provided when crossing alongside main street traffic since the main street approach does not have vehicular actuation.  However, when the APS device is provided and the traffic signal is coordinated or on a fixed cycle, the accessible indication will not initiate until the next cycle when the pushbutton is pushed.  Therefore, actuating the pushbutton will provide no information until the next signal cycle is started.  Pedestrians may assume the pushbutton is not working and attempt to cross without the aid of the APS device.  When the pushbutton is pushed, appropriate messaging is recommended as a speech pushbutton information message to indicate that the signal provides a walk interval on the next cycle.  When this type of signal phasing is used, appropriate communication between the APS device and the signal system should be evaluated.


Another scenario caused problems with pedestrian signals that rest in WALK or DON’T WALK.  A signalized intersection included a pedestrian signal to cross the side/minor street that rested in DON'T WALK unless the pedestrian pushbutton was pushed to cross that street.  This signal had coordination and a fixed cycle.  When the pushbutton was pushed, two results could occur: 1) if the button was pushed during the side street phase, the WALK was displayed at the start of the corresponding main street phase for a minimum time followed by the Flashing DON'T WALK and the steady DON'T WALK; 2) if the button was pushed during the corresponding main street phase, the WALK was displayed only if there was enough time for the WALK and Flashing DON'T WALK time prior to the force-off period allowed by the coordination.  This installation required a time period or “window” at the beginning of the main street phase which was the only period that would allow the WALK to come up while in that phase; otherwise, the WALK would not come up until a side street phase started and terminated, i.e., the next signal cycle.  Therefore, a pedestrian could activate the pushbutton and not receive a timely walk interval.  Again, a pedestrian may assume that the push button is not working under this condition.
 

Speakers/Volume

A Maryland installation experienced problems adjusting the volume of a unit that used the APS control units installed in the controller cabinet (rather than the pedestrian signal head).  Because of the distance, the wiring was too small of a gauge to drive the speaker and provide a loud enough message, compounded by the pole and speaker being more than 10 feet back from the crosswalk.  Manufacturer’s guidelines and specifications should be followed for proper operation.  However, there were also concerns and constraints on the amount of room for new wiring in the conduit. Speakers can be provided for each control unit. 


Pedhead mounted speakers in existing installations are often mounted in positions that make the messages ambiguous.  The speaker should be as close as possible to the crosswalk being signaled by the speaker and speakers should be separated by 10 feet, if possible.  For pushbutton integrated devices, the speaker is in the pushbutton housing.  The location of the pushbutton and orientation of the speaker can be critical to hearing the WALK indication at the beginning of the crosswalk. 


Although current standards call for the APS volume to be 2 to 5 dB above ambient sound and for the locator tone to be heard from 6 to 12 feet from the pushbutton, volume is often set much louder than that.  Installers are used to devices using audible beaconing and think that APS are supposed to loud enough to hear across the street.  While the locator tone and WALK indication volume can be measured on the street, it is difficult to get an accurate reading, because of the short duration of the tones or messages and their response to ambient noise.  Installers need to understand the distance requirements for audibility of the locator tone and make adjustments to the devices.
 

Speech Messages

The speech messages used for the WALK indication, as well as the descriptive pushbutton message, must be understandable.  Some problems have been reported.  An example of this was found at an intersection where the poorly recorded WALK messages made the street names indistinguishable [“Pratt” and “Calvert”].  The recordings were made in-house and the quality of speech and accent were poor.  Digital speech messages can be downloaded from an AT&T web site and use of those may be appropriate.  Consistent wording and properly recorded messages are necessary for intelligibility in noisy street conditions.


Speech messages have been suggested as one method to solve problems with ambiguity when two pushbuttons were mounted on the same pole.  The speech WALK message that provided the street name was supposed to clarify that the WALK message applied to the street that the pedestrian wanted to cross.  However, if the speech message does not clarify which street the button applies to, the speech WALK message using the street name does not clarify which street has the WALK indication to a pedestrian who is unfamiliar with the intersection.  For example, at the intersection of Harford and Taylor Streets in Baltimore, the pushbutton message just said “Harford and Taylor” (both street names) for all devices. The speech WALK messages said “Walk sign is on to cross Taylor” or “Walk sign is on to cross Harford.”  This didn’t resolve the ambiguity problem for users who were unfamiliar with the intersection and not sure which street they were crossing, or who did not know which street the pushbutton applied to. 


Polk County, Florida wanted to use a male voice for one crossing direction and a female voice for the other.  The theory was that this difference would distinguish crossing directions and add to the safety of the crossing.  Most devices provide self-recorded messages capability; however, care should be taken in recording messages, in terms of quality, and wording, and particularly ambiguity.  Separate poles may be the best solution.


Other minor problems relate to the recommended messages not being used; there is no standard WALK message or standard pushbutton message. Older installations require updated messages consistent with current MUTCD standards.  Recommendations for specific wording for speech messages were developed in January 2002 in a report on speech messages prepared by Accessible Design for the Blind (6).  Most problems can be resolved by use of wording consistent with messages developed in that report, available online at www.accessforblind.org.

 

Pushbutton and Tactile Arrow Location

The blind pedestrian must push the button, then line up to cross the street.  Some problems have been observed in locations of pushbuttons and poles supporting APS devices.  Pushbuttons installed without locator tones may make it impossible to determine that there is a button that must be activated to call the WALK.  Many problems exist with pole locations.  Poles that are more than 10 feet from the curb line provide real problems activating the pushbutton and then realigning to cross the street.  Pushbuttons are often placed in positions that are not reachable from the sidewalk area, are in the bushes, or behind a fence.  Stub poles may be needed from some locations.  Separating devices on separate poles provides greater effectiveness.


If the original installation specification was not correct, it may limit the arrow direction and location possibilities.  The tactile arrow is supposed to point in the direction of travel on the crosswalk and the face of the device is supposed to be parallel to the crosswalk it controls.  Some installations have the pole in a poor location, back from the street with the arrow pointing at the street and aligned with the crosswalk direction, but not within the crosswalk area.  In other locations, the arrow has pointed a diagonal to the path that should be taken to cross the street.  If installers do not understand the arrow’s alignment, they may install it in the wrong direction, particularly if they use the holes from the previous pushbutton.

 

Braille Signage Installation

Braille indications on the pedestrian signals have been found mounted backwards or with the Braille label for the wrong street.  Manufacturers ship them with a label to clarify positioning; however, technicians may make adjustments to the sign and reverse or mix up the Braille plaques. 
 


APS PRODUCTS AND MANUFACTURER INFORMATION
 

Figure 3 presents a product matrix that lists various types of APS products and their associated Walk indication and other features, as of March 2003. [text version]
 

Matrix of Accessible
Pedestrian Signal Functions

TYPE

Pedhead mounted

O

X

X

O

X

X

Pushbutton integrated

X

O

O

X

X

X

Vibrotactile

X

Receiver based

X

X

WALK INDICATIONS

Tones

X

O

X

X

X

X

X

X

X

Speech messages

X

O

O

X

X

X

X

Vibrating surface

X

X

O

X

X

O

O

Message to receiver

X

X

Audible beaconing

O

X

X

O

OTHER FEATURES

Pushbutton locator tone

X

X

O

X

X

X

Tactile arrow

X

X

O

X

X

X

Pushbutton information message

O

O

O

O

Automatic volume      adjustment

X

X

X

X

X

X

Alert tone

O

X

Actuation indicator

X

O

O

X

X

Tactile Map