How-To Hit Green Lights
When I was a kid, I thought my aunt was a witch. Not a broom-riding, cackling, pointy-hat-wearing witch, but a normal-looking witch with special powers.
At least that’s what she told me.
As a six-year-old, I watched her take out her teeth and make slugs disappear by pouring salt on them. In the days before Photoshop, she had a two-headed photo of yours truly hanging on her wall.
The most amazing thing, though, was the way she could make the traffic lights through downtown Decatur magically change from red to green just as we started to buzz through on Main Street, south of Eldorado Street. Or so she said.
Turns out that was being done by the City of Decatur, not my aunt’s witchcraft.
“Some systems are timed (because) it’s more efficient to move cars,” says City Engineer Matt Newell. “If cars don’t have to stop and start, they save gas and it’s safer.” Frequent and unexpected stops also increase the likelihood of cars running into each other.
Many Decatur traffic lights are timed to allow cars to progress with as few stops as possible based on speed estimates and estimates of how many cars will be stopped at lights at any given time. Eldorado Street from Fairview Avenue to Jasper Street, Main Street north and south downtown, and Pershing Road from Main Street to Woodford Street are among Decatur’s major thoroughfares with timed signals.
Some intersections, like those at Mound Road and U.S. 51 and Ash Avenue and U.S. 51, are defined “traffic responsive,“ with camera sensors that add or deduct time from green lights based on traffic conditions. There are also a number of synchronized ”subsystems” throughout the city, such as the four sets of lights at South Shores Plaza — multiple lights in a specific area coordinated to maximize traffic flow and lessen the chances of traffic jams.
Local legend has it that motorists traveling at a particular speed can catch all green lights from Hickory Point Mall to Decatur’s south side, and along Eldorado Street from Fairview Avenue to Nelson Park. Estimates of the perfect speed have ranged from 28 to 40 miles per hour.
According to Newell, most signals are timed to progress based on estimated vehicle speeds of just less than 30 mph so, in theory, both are possible with a little luck and the right traffic patterns.
Driving 28 miles per hour south on U.S. 51, my wife and I were caught by red lights at the Mound Road, Garfield Avenue, McKinley Avenue, and Eldorado Street intersections and passed through green lights at Pershing Road, Grand Avenue, Marietta, and Green Streets, and every light south of Eldorado downtown.
Needless to say, there were a lot of unhappy motorists stuck behind the guy driving 28 on a major city thoroughfare. The speed limit varies from 30 to 45 miles per hour along the route and, when driving the posted speed limit on a later trip, I made every light except one.
“(The system’s) timed to allow a significant amount of cars (to pass) without having to stop more than once or twice,” says Newell.
“It’s easier downtown because of one-way traffic, while on Eldorado, you have to allow cars from each direction to go through and turn.
“Somebody’s got to stop.”
Following his timed-travel experiment, Contributor Billy Tyus concluded that driving at — or very slightly above — posted speed limits is the way to go.
This article originally appeared in the August/September 2009 issue of Decatur Magazine. It may not be reproduced or redistributed in whole or in part without the publisher’s consent.
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