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  • High-Speed Camera System Takes Its Toll on Violators

Photonics Spectra
Sep 1999
Daniel C. McCarthy

Motorists traversing the Golden Gate Bridge to San Francisco may take comfort in knowing that the structure has endured the 1989 Loma Prieta earthquake, scouring ebb tides and the passage of nearly 1.5 billion vehicles. In contrast to the bridge's structural dependability, however, are its toll collection facilities, which officials describe as antiquated.

Digital cameras from Tecnicon will help capture information about toll violators on San Francisco's Golden Gate Bridge. The image here demonstrates capture of a vehicle traveling at 70 mph. Courtesy of Tecnicon International.

That could change later this year, when bridge authorities hope to introduce a state-of-the-art facility implemented by TDC Inc. The new toll registry system will incorporate automated violation enforcement in the form of digital cameras from Tecnicon International Inc. that capture images of license plates as they pass. Each of the 11 southbound lanes will be equipped with a 1280 x 1024-pixel camera that operates at up to 20 frames per second.

Motorists must stop to pay either a human or automated attendant, and a computer processes the transaction. By the time a vehicle is moving again, the system has determined whether the transaction is valid or not. As it exits the booth, the vehicle passes through a curtain of light created by a vertical row of 120 infrared light-emitting diodes. Its passage between these diodes and a corresponding array of photodetectors allows the system to record the vehicle's size and speed. It also triggers the camera if the computer registers an invalid transaction.

Toll violation has not been a major problem on the Gold-en Gate Bridge, according to Mary Currie, public information director for the Golden Gate Bridge Highway and Transportation District. Most often the motorist has forgotten a wallet. In these cases, the bridge officer handwrites the license plate number so that the toll can be collected by mail. Once installed, the electronic toll collection facility will record this information automatically with the snap of a camera.

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