Seattle Tracks License Plates on Streets to Calculate Travel Times

City leaders claim Seattle is the first in the nation to use license plate reading cameras on city streets to determine how long it takes a car to get from points A to B.

by / October 20, 2010
Electronic signs show commuters travel times by reading license plates. Photo courtesy of the Seattle Department of Transportation Seattle Department of Transportation

Seattle commuters no longer have to guess how long it will take to get across town. To get accurate travel times in real time, they simply need to read the electronic signs.

This intelligent transportation system feature, unveiled Monday, Oct. 18, by the Seattle Department of Transportation (SDOT), uses license plate reading cameras to calculate how long it takes a car to get from points A to B. In the city’s Traffic Management Center operators capture and display the data to the signs during peak commute hours, making Seattle the first in the nation to use this technology on surface streets, according to Adiam Emery, SDOT’s intelligent transportation system project manager.

“We’ve seen a lot other estimated travel times with other devices and travel time information on freeways,” Emery said. “But we’re the first to use license plate readers to deliver travel times on city streets.”

Currently at five locations in the city, the electronic signs are part of SDOT’s nearly $19 million intelligent transportation system. The Washington state Department of Transportation funded the bulk of this project, Emery said, in an effort to help minimize congestion caused by construction of the Alaskan Way Viaduct.

Installations will continue through the spring for a total of 22 information signs (not all will display travel times) and 130 cameras. The signs will be active during rush hours in the morning from 6 to 9 a.m., and afternoon from 3 to 7 p.m. The system also has an algorithm that can detect random congestion during off-peak hours and trigger the signs, Emery said. But the cameras will be on all the time and automatically generating travel information, which citizens can access 24/7 via iPhones and SDOT’s website.

The city’s intelligent transportation system represents the latest in a nationwide trend to enhance travel data with technology. By early 2011, motorists on busy roadways in New Jersey will have access to a high-tech tool that forecasts potential congestion up to 10 minutes in advance, much the same way meteorologists forecast the weather.

SDOT officials said the license plate readers eliminate the guesswork by providing actual real-time data. If the system can’t find any plate matches between two points, no data will be available.

As for the license plate numbers, Emery said, SDOT deletes them immediately once the department captures the travel information.

“Once we make a match, the data from the camera is destroyed,” Emery said. “We don’t retain the license plate information.”

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