New software may smooth out traffic snags

The city will spend $150,000 on software to adjust signals at 10 major intersections that now trip (automatically recalibrate) to accommodate emergency vehicles. The new software will enable the signals to re-cycle back to their original timing faster after an emergency vehicle clears the intersection.

The current system can take as long as 10 minutes to recover to an established pattern synchronized with other signals along the corridor, Public Works Director Tom Black said.

"It's taken seven or eight cycles at times and we're almost at gridlock at that point," Black said. "Now it goes back to the right cycle within one cycle, less than a minute and 10 seconds."

Preemption signals are stationed all along Medlock Bridge Road at major east-west intersections that carry almost as much traffic. When the signal timing is altered, especially at rush hour, it can create massive delays, Black said.

"Sometimes it takes an hour to clear all that," he said. "It's just a mess. "

Since its founding five years ago, Johns Creek has placed special weight to almost anything related to emergency services.

Its police and fire departments consistently rank among the highest in the state and to improve their response times, the city launched its own 911 system with Sandy Springs three years ago.

Preemptive signals are not prevalent in metro Atlanta. DeKalb County has 29 priority signals on Memorial Drive that improve the chances for a green light for approaching MARTA buses, but their impact on traffic is minimal, said spokesman Burke Brennan.

"In certain cases, it's noticeable, but half the time the buses hit [green lights] anyway," he said. "We've only had a few complaints."

County Johns Creek's preemptive signal system was installed last year with a $572,000 grant from the Federal Emergency Management Agency.

Georgia DOT spokesman Mark McKinnon said the state is aware of delays created by preemptive signals and engineers know of no way to correct it without the added expense of the new software. But even without the upgrade, preemptive signals have proven their value, he said.

"I think most citizens would agree it's a good thing and be willing to spend  a couple of extra minutes in traffic to let those emergency vehicles do their jobs," he said.

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