William Gerrey
The Smith-Kettlewell Eye Research Institute
Rehabilitation Engineering Center
April 7, 1992
What do sighted people know as they approach an intersection? They know the names of the streets they may catch a glimpse of an address number which orients them in the City's scheme of things they see the presence of a crosswalk or the lack of one and white lines tell them crosswalk directions. Observing traffic patterns and noting the presence of walk/wait signs, they know if the intersection is controlled by a signal: they also, with a quick glance, determine whether or not the signal is controlled by a pushbutton. What do blind people know as they approach an intersection? They know by listening to traffic patterns whether or not the intersection is controlled by a traffic signal. Where intersections involve three or more streets, the listener can at least determine that it is a complex intersection. By noting the direction of signal controlled traffic, the times when it is permissible to cross can usually be determined. The blind traveler may not notice the pushbutton if there is one. He may not know the name of the street he is crossing. To lean an address number, he must find an open establishment and ask the proprietor.
There are systems of audible traffic signals. These tell the blind traveler whether or not a traffic signal has changed. The audible tones they produce, however, cannot easily be localized they do not tell the traveler precisely where the crosswalk is or where it leads. Furthermore, they provide no information as to the number of streets involved, the names of the streets, or the location in the grid of addresses -- and if a pedestrian button must be pressed to actuate them, the traveler may be unaware of their existence.
Talking Signs® go beyond the concept of mere indicators. They are a full-featured information system. Recognizing this, Mr. Gordon Chester of the Department of Parking and Traffic specified a design which would give the user six pieces of information:
1. The name of the cross-street can be heard through the user's receiver. (The name of the street parallel to his direction is heard when the receiver is pointed across that street.)
2. The address number of the block ("zero hundred block," "100 block," etc.) is also announced through the user's receiver.
3. Since Talking Signs® use directed beams of infrared light, the direction the user's receiver is pointing is also announced (facing southwest, for example).
4. The "color" of the light controlling the traffic is announced ("red," "green," or "yellow").
5. The crosswalk information is transmitted via a narrow beam which is confined to the boundaries of the crosswalk. Therefore, when red, green, and yellow information is heard, the traveler knows that he is in the crosswalk.
6. By scanning the receiver left and right, the precise direction along the crosswalk is indicated: the user searches for the clearest signal.
Another consideration in choosing aids for the blind d traveler is the intrusion caused by their presence. Where audible traffic signals have existed (such as San Francisco's early experiment at 7th and Howard Streets, which used a bell and a buzzer), residents have insisted that they be turned off at night: At the very least, they draw attention to the accommodation made for the blind traveler.
The receiver of the Talking Signs® system is a personal listening device. Its small speaker is in the hand of the user and causes no high-volume signal to be produced for others to hear. Furthermore, if the traveler is familiar with all aspects of an intersection which he uses regularly, he may choose not to actuate the receiver at all; but to depend on standard mobility skills to negotiate the intersection.
Finally, since Talking Signs® are substitutes for print information, they are of use to a much larger population than the blind because they speak the names of streets and address numbers, they address the needs of the print-handicapped as well. Other services, such as closed-circuit newspapers by radio and the Talking Book library, have expanded to their current levels because of their use by the print handicapped.
In choosing adaptive equipment for San Francisco's blind visitors and citizens, please consider the importance of information content available from them. Technology now permits speech to be stored in computer chips (rather than on tape machines with moving parts), and the print-handicapped or blind travelers' aids can be much more informative than simple indicators of the past.
(The following resolution was subsequently adopted by the San Francisco Board of Supervisors on April 13, 1992)
"Resolution urging the Mayor to urge the Parking and Traffic Commission to implement a program to install Talking Sign devices at traffic signals in those portions of the city that are heavily used by pedestrians, and at locations where it is generally known that significant numbers of visually impaired pedestrians cross the streets."