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Emissions And Enervation

New ideas for battling traffic can’t come fast enough. The Federal Highway Administration estimates that U.S. drivers spend 4.3 billion agonizing hours each year stuck on clogged roads. The average American now spends 36 hours per year stuck in traffic, up from 11 hours in 1982, according to a Texas Transportation Institute study released in May. The U.S. Environmental Protection Agency says tailpipe emissions are responsible for about 58 percent of U.S. emissions of carbon monoxide, 30 percent of nitrogen oxides and 27 percent of volatile organic compounds, among other pollutants. These bleak realities prompted Congress
to begin funding embedded sensor systems in 1991. But while the resulting “Intelligent Vehicle Highway Systems Program” did unleash technology against traffic, it was technology developed in the 1980s. Today, only about 10 percent of U.S. highways contain these sensors, a figure expected to increase to no more than 20 percent by 2020. Although the benefits of these systems vary by city, studies have generally shown they mostly help by speeding emergency response, with no hard proof that sensors have improved travel times.

All of which leaves the fast lane open for a wholly new approach to traffic management, one where radio waves replace magnetic loops as the key sensing technology. The clear leader of the wireless pack, experts say, is the cell phone. It was the mobile phone, after all, that first beat roadway sensors to the punch: drivers simply began calling 911 to report accidents they’d witnessed. Today, every American hillock, church steeple and high-rise seems to have sprouted a cellular radio transmitter and antenna.Americans own about 111 million cell phones-almost one for every two people-with 46,000 new subscribers every day, according to the Cellular Telecommunications & Internet Association, a trade group in Washington, DC.

Transforming this wireless communications infrastructure into a trafficsensing tool is the next step. Radio waves emitted by a driver’s cell phone during ordinary conversation can be used to pinpoint not only a car’s location but its speed and direction, too. The first application will be for emergency use: the federal government is requiring that, by October 2001, cell-phone companies be able to provide precise mobile-phone location when a 911 call is made. Eventually
these new location technologies could greatly extend and enhance today’s intelligent-highway infrastructure, too.

The leading approach to analyzing cell-phone signals to detect traffic patterns exploits the fact that these signals have distinct “fingerprints” that change as the phone’s location changes. That’s because a mobile-phone signal bounces off buildings, hills and other obstacles before converging on a cell tower, producing
a unique signal pattern for every spot along a roadway. Once these fingerprints are mapped and stored in a database, it’s possible to create software that
analyzes the signal of a passing cell phone-by sampling it several times per minute-to determine a car’s exact location, direction and speed.

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