egI introduction

Crossing points are the places in any journey where the traveler is most vulnerable to danger in the form of collisions with passing vehicles which can result in serious injury or death. This significance is widely recognized by blind persons themselves, and by Orientation and Mobility Specialists, who instruct blind persons in independent travel, and who spend a good deal of their instructional time teaching techniques for street crossings.

At signalized intersections in busy urban areas, many confusing cues are presented to the blind traveler who must rely primarily on traffic sounds to determine the geometry of intersections, the nature of traffic control, and when it is safe to cross. The usual cue for determining when it is safe to cross at signalized intersections is the detection of surges of traffic beginning to move parallel to the pedestrian's direction of travel. However, anywhere that turns are allowed, safety is not assured by this cue. In addition, even for the most experienced traveler, there are certain things which can not be determined by sound, such as whether a median or turning island exists. Having full access to all information about intersection geometry and traffic control lowers the risk of making an inaccurate judgment.

Progress has been made in avoiding many of these ambiguities through the deployment of prototype Talking Signs® units at signalized intersections in downtown San Francisco. The application involves providing two types of information to pedestrians. The first tells the user where he or she is located; it is comparable to the information posted on the visual street signs at each intersection. The repeating message users hear from the speakers of their hand-held receivers when they are walking down the sidewalk is, for example, "Traveling East on the 800 block of Grove Street toward Larkin Street." When users near the curb, another message is heard. This "pedestrian crosswalk indicator" message tells users the condition of the pedestrian signal. It repeats, for example "Wait... Larkin Street" or "Walk Sign.... Larkin Street," the particular message depending upon the status of the visual walk/wait sign (see Figure 1). This message can be heard only if the pedestrian is in the crosswalk. Thus the Talking Sign not only tells the pedestrian the current status of the pedestrian cycle but also aids in finding the crosswalk and the direction of the destination corner.

Sighted pedestrians not only have access to the information on the street signs and the "walk/don't walk" sign but they also have specific information about the characteristics of an intersection such as turn lane, mid-block crossing, cut-through island, pedestrian actuated 4-way walk signal, free right turning lane, short walk cycle, use of pedestrian push button at island for walk signal to cross second half of street, etc. Talking Signs® can incorporate extended messages which communicate special attributes about an individual intersection following the street name on the approach message. Alternatively, this additional information may be provided through a different receiver channel.

Figure 1. Talking Signs not only gives location information but also tells the pedestrian the current status of the pedestrian cycle, aids in finding the crosswalk, and indicates the direction of the destination corner.

The Talking Signs remote infrared signage technology has been under development and testing at The Smith-Kettlewell Eye Research Institute for the past twenty years. The Talking Signs system is comprised of infrared transmitters which convey speech messages to small, hand held, receivers carried by blind travelers. Infrared transmission is directional. This means that when blind Talking Signs users pick up a message, they can also tell where it comes from. The message is coming from the direction in which they are pointing when they hear the message clearly. These repeating, directionally selective voice messages are transmitted by infrared light (940 nm, 25KHz). The directional selectivity is a characteristic of the light message beam; the clarity of the message increases as the sign is "pointed at" or approached. This ensures that the people using the Talking Signs system have information available about their relative location to the goal as they move towards it. Travelers who are blind can get to the destination by walking in the direction from which they receive a clear message. They do not need to remember directions. They just travel toward the sign they hear, in the same way that sighted people travel toward a sign or landmark they see.

Under a license to Talking Signs, Inc., the Talking Signs system has been manufactured and marketed for the past six years. During the last three years of human factors research we have established that blind people traveling in a variety of environments using Talking Signs can easily learn to use the system effectively (Bentzen, Crandall, & Myers, 1997; Bentzen & Mitchell, 1995; Crandall, Bentzen, Mitchell, & Rosen, 1994; Crandall, Bentzen & Myers, 1995a; Crandall, Bentzen, & Myers, 1995b; Crandall, Bentzen, Myers & Mitchell, 1995). The Talking Signs system is currently in use in transit settings at both indoor stations and outdoor platforms, and at bus stops. It has been evaluated and found effective in locating buses and bus stops.

In the field of traffic control systems, Talking Signs, Inc. has licensed the production of a Talking Signs module which is affixed to existing "ped heads" and is electrically connected to the existing "ped head" lamp circuit by four wires.

Talking Signs is an electronic orientation aid used to assist in orientation and navigation (see Figure 2). The system is an information system-it is not a safety system. It is not a substitute for travel aids such as the long cane or dog guide, or for the use of other sensory information or good spatial reasoning.

This study, which evaluated an installation of numerous Talking Signs equipped pedestrian signals within Civic Center area of San Francisco, developed out of a succession of experiences enumerated below. That is, the final message strategy selected for evaluation (the four components of messaging being: wording, location, direction and beamwidth) evolved over the past six years. As a basis for a refined development, a Focus Group comprised of professionals who had evaluated an early prototype remote infrared signage system (RISS) "ped head" system (installed in San Francisco six years prior), was convened at San Francisco's Lighthouse for the Blind. This group was made up of blind pedestrians, leaders of agencies serving people who are blind, service organizations for people who are blind, teachers of blind persons (O&M Specialists), and rehabilitation engineers.

The messaging parameters established by this Focus Group were organized into a survey and presented to 46 blind travelers, orientation and mobility specialists and technical specialists. Members of the national survey group were offered various permutations of messages from which to select preferences. Data from the 29 respondents were analyzed in order to establish the most favored message structure and content. These results were then pilot tested with the aid of three blind travelers. Results of the study were then prepared in monograph form for distribution to interested parties, including our collaborators; Talking Signs, Inc. the San Francisco Department of Parking and Traffic and the licensee of the prototype units.

Final message
As users come within 150 feet (of one example intersection), their receivers provide them with orientation information: "Traveling East on the 800 block of Grove Street toward Larkin Street." Then, as users near the curb, another message is heard. This "pedestrian crosswalk indicator" message tells users the condition of the pedestrain signal. It repeats, for example, "Wait... Larkin Street" or "Walk Sign.... Larkin Street." We determined in our interviews, Focus Group and survey that this would be the least ambiguous information. "Walk sign" does not say "Walk" -- It says, in effect, "the visual pedestrian signal indicates that the traffic control signal for vehicles has switched to allow pedestrian use of the crosswalk." Of course, this doesn't mean that a car cannot make a right turn into a pedestrian during the "walk sign" phase. In this sense, the blind pedestrian must be especially vigilant when negotiating intersections. It is for this reason that all agreed that a false sense of security (which would potentially be encouraged by a simple "walk" message) could be mitigated by transforming the "walk" to "walk sign." "Walk sign" is not a command or instruction to walk; it only indicates the signage information available to the sighted pedestrian. (See Figure 2).

Figure 2. Separate messages come from the front and rear of the Talking Signs unit; the “orientation message” tells the users where they are (“Traveling East on the 800 block of Grove Street toward Larkin Street.”) and the “pedestrian crosswalk indicator” message tells users the condition of the pedestrian signal (“Wait... Larkin Street” or “Walk Sign... Larkin Street”).

From these results a new prototype "ped head" transmitter module implementing the recommended messaging features was fabricated. Twenty-nine experimental prototype units were installed at intersections for testing in San Francisco's Civic Center area.
In addition to the messages described above, participants had access to information which was specific for each of the four intersections. This Auxiliary Message was functionally equivalent to a "second channel" originating from the opposite corner (pedestrian crosswalk indicator) and was activated by a switch on the receiver. Alternatively, this Auxiliary Message could be supplied as part of the standard orientation message.