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Traffic Lights Evolve

New traffic light at MacArthur and Clara Barton Parkway equipped with small computer.

— The new traffic light installed at MacArthur Blvd. and Clara Barton Parkway earlier this month is a smart light.

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Photo by Ken Moore

The new traffic light at MacArthur and Clara Barton Parkway.

Traffic signals have evolved with new technology, according to Bruce Magnum, of the Transportation Systems Engineering Montgomery County Department of Transportation. While earlier traffic lights were controlled mechanically, a small computer controls newer traffic lights, he said.

The light at MacArthur Boulevard and the Clara Barton Parkway will be fully actuated with vehicle sensors on all three sides. Because this light won't be interacting with other lights on arterial roads, it won't have to be coordinated and can be controlled by whether there are vehicles at the intersection, said Magnum.

THE SIGNAL is ready to go but is now waiting for power, and that's up to Pepco, said Magnum. No matter how far in advance the county notifies Pepco that it is installing a light, it is always somewhat unpredictable and always takes some time to get power installed.

After the light is operational, a county traffic engineer will observe how it functions in the first peak periods, morning and night, and make adjustments as needed, according to Magnum.

“A traffic signal is not a panacea,” said Magnum.

Data collection and analysis was conducted by the Montgomery County Department of Transportation.

New traffic signals are installed at intersections that qualify based on number of vehicles, the number of accidents and the amount of delay; those are called warrants.

The engineering department designs and installs the light once a light is determined to be needed.