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What's Next: Street Smarts: A Device to Help the Blind Find Crosswalks

December 2, 2004
By IAN AUSTEN





CROSSING busy roads can be a challenge for people with good
vision. For blind people, it is a perilous activity.

"I know a number of blind people who have been hit by cars
over the last year while crossing roads," said Jay
Leventhal, the editor in chief of AccessWorld, an online
technology magazine published by the American Foundation
for the Blind.

While American cities are, in Mr. Leventhal's opinion,
generally poorly equipped to deal with blind pedestrians,
some technologies have been introduced in recent years to
remedy that situation. Most notably, San Francisco, New
York and some smaller cities have equipped traffic signals
with what Mr. Leventhal calls "chirping birds," audio
versions of green and red lights.

Now, researchers in Japan have developed a software system
for detecting crosswalks that may help the blind when
crossing streets. The system, developed by Tadayoshi
Shioyama and Mohammad Shorif Uddin at the Kyoto Institute
of Technology, takes images of the street with a camera;
the software then determines if there is a painted
crosswalk in the image.

A fixed camera is used now, but Dr. Shioyama said that
eventually, a miniature digital camera and processor could
be fitted into a pair of eyeglasses. When a blind person
wearing the glasses came upon a crosswalk, the system would
alert the user through a synthesized voice piped through a
small speaker.

For now, the software can recognize and measure only a
style of crosswalks not commonly used in North America.
Known as zebra crossings in Britain, they feature a series
of thick white bands that run in the same direction as the
vehicle traffic.

Greatly simplified, the software effectively draws a
virtual line out into the road. If a crosswalk is present,
the edges of the painted white lines will form a
predictable series of points along the virtual line.
Because passing road traffic disturbs the pattern, the
system can analyze several images before deciding whether a
crosswalk is present.

In a paper published last month in the British journal
Measurement Science and Technology, the researchers
reported that the software correctly identified 194 of 196
crossings it analyzed in tests. In the two failures, the
software reported that there were no crosswalks when there
actually were. (The researchers said the system was
designed to err on the side of denying a crosswalk's
existence, so, as they put it in the journal, "there occurs
no dangerous error.")

The two researchers also plan to combine their software
with an earlier system they developed for detecting the
color of traffic lights.

The crosswalk detection system works best with bands that
are precisely painted on smooth pavement. While neither of
those conditions are a problem in most of Japan, they are
in parts of the United States.

The crosswalk identification software is not Dr. Shioyama's
first project to aid blind people. In the past, though, he
has concentrated on ultrasound for navigation,
incorporating an ultrasonic transmitter-receiver into a
cane. The idea is that the ultrasound signals bounce off
objects and back to the user. By sounding an alert or
vibrating when certain reflections are received, the device
can warn of obstacles.

Ultrasound has been favored by other researchers and
companies in their devices to aid the blind. The
SonicGuide, for example, is a pair of eyeglasses fitted
with an ultrasound transmitter and tiny speakers. The Mowat
Sensor is a hand-held ultrasonic way finder. And the
Navbelt has an array of ultrasound transmitters that a user
wears around his waist to create an audio panorama of his
surroundings.

But none of those devices are able to specifically identify
a crosswalk, nor do they have the potential for figuring
out the state of the traffic signals.

Other researchers had explored the idea of using cameras to
detect crosswalks. All of those systems rely on two cameras
to generate a stereo image. But Dr. Shioyama wrote in an
e-mail message that it could be hard to keep two cameras
aligned and calibrated.

Mr. Leventhal said that the crosswalk system seemed valid
in concept, although he noted that the blind pedestrians in
the greatest danger are those who must cross wide, busy
roads that lack crosswalks or even traffic signals.
Similarly, the software cannot identify cars making right
turns into crosswalks against red lights, another dangerous
situation for blind people.

From a practical standpoint, Mr. Leventhal said he wanted
any crosswalk system to be included in one of the Global
Positioning System devices now on the market to help guide
people with little or no vision. VisuAide's Trekker, for
example, combines software with a PocketPC-based hand-held
computer, a G.P.S. receiver, a battery pack and a small
speaker.

Devices like these, Mr. Leventhal said, are very good at
giving locations and directions. But the limitations of
G.P.S. technology mean that they cannot pin down the
location of a curb or crosswalk and frequently fail in
areas such as Manhattan that have many tall buildings.
Integrating image analysis software might overcome that,
Mr. Leventhal said. But the key word, he added, is
integration.

"Blind people have to carry so many things around already,"
Mr. Leventhal said.

Ultimately, he said, the best solution is to design roads,
sidewalks, traffic signals and crosswalks with blind users
in mind.

"Traffic lights are there for a reason," he said. "I don't
see why blind people shouldn't have the same kind of
precautions as there are for sighted people."

http://www.nytimes.com/2004/12/02/technology/circuits/02next.html?ex=1103024
521&ei=1&en=468768362b031960


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