The new variable speed limit signs on the top end of I-285 rise and fall between 65 mph and 35 mph, and most drivers find them confusing, annoying or worse.
“Shame on whoever approved this!” said Atlanta resident Ari Jones, who travels on the Perimeter to Sandy Springs for work each day. “It’s just mass chaos.”
“It’s not working and is a total waste,” said Peter Sway, who found plenty of company among AJC Facebook commenters this week. Only three of 78 people had good things to say about the signs, which have been up for 10 days.
And it’s disconcerting to be cruising down the Perimeter at 65 and see the digital sign drop — by 10 mph increments — to 35 mph. But here’s the trick: the signs don’t reflect traffic conditions where you are, but where you’re about to be.
Commuters might find that a little too existential. And state transportation officials say they expected some initial resistance from motorists.
But they are urging drivers to give themselves a chance to adapt before drawing conclusions about the value of the $4.9 million investment.
How it works
The first variable speed limit system in Georgia took effect Oct. 5 on the 36 miles of I-285 that lie north of I-20. The top end was chosen since it carries between 50,000 to 100,000 more cars, depending on the segment, than the south side of I-285. In addition, the risk of crashes increases with the number of interchanges, and the top end has almost twice as many as the south end.
GDOT already had traffic detection stations spaced at regular intervals along I-285. The stations count vehicles and measure their average speed. The 88 pairs of new variable speed limit signs (one installed on the barrier wall, another on the shoulder) are programmed to change based on average speed readings from traffic detection stations about a mile ahead.
When a speed change is needed, the sign on the shoulder communicates that to the sign on the barrier wall via a radio-controlled signal.
If there is heavier and slower traffic down the road, the speed limit will decrease in 10 mph increments from 65 mph to as low as 35 mph.
“So if you are driving, and you see that progression, you know you are about to hit traffic,” said Mark Demidovich, assistant state traffic engineer.
The system is designed to smooth stop-and-go traffic and reduce accidents by slowing drivers before they hit a jam. That way, they can avoid slamming on their brakes or weaving dangerously.
Some signs have malfunctioned during the first days of the program’s implementation, said Demidovich. Four pairs had problems communicating with each other. The four signs along the barrier wall were displaying different speed limits from the corresponding signs on the shoulder. That left drivers scratching their heads about which one they should obey.
The radio-controlled parts of the four signs were replaced overnight Tuesday, Demidovich said.
Some drivers remain skeptical about the motive for the speed limit reduction. Numerous commenters on Facebook suspected it was a ploy for police to generate more speeding ticket revenue.
GDOT spokeswoman Karlene Barron said that’s not true. If it were, the department wouldn’t have raised the speed limit on I-285 under normal conditions from 55 to 65 mph, she said.
The Georgia State Patrol and Doraville Police are giving drivers a 60-day grace period before writing tickets for failure to obey the variable speed limit signs. (Although they caution that grace period doesn’t mean people driving over 80 mph when speed limits are set on the normal 65 mph rate will get a free pass).The state patrol doesn’t receive revenue from tickets anyway, said GSP spokesman Sgt. Les Wilburn. That money goes instead to the county or city where the traffic stop occurred, Wilburn said.
The speed increase, at least, has spurred enthusiasm among weekend and evening drivers who thought a 55 mph limit on I-285 was far too slow.
“I’m traveling early in the morning at 3 or 4 a.m. when it’s completely dead on the road,” said Patrick St. Fleur, an Atlanta corporate banker who often catches early flights out of Hartsfield-Jackson International Airport.
St. Fleur loves the variable speed limits. “There’s no reason to have a speed limit of 55 when there is nobody on the road.”
Does it work?
Variable speed limits are common in Europe and Australia, but still relatively new to the United States.
This pilot project in Atlanta is patterned after similar systems in Seattle, Orlando and other cities.
After variable speed limits were implemented on I-5 in Seattle, collisions declined by up to 7 percent on weekdays and up to 20 percent on weekends, according to the Washington State Department of Transportation.
But they aren’t a panacea for traffic tie-ups.
The public and law enforcement were widely dissatisfied with a variable speed limit system along one corridor in St. Louis six years ago. The speed limit changes, mandatory for the first few years, were later down-graded to “advisory.” Still, they did not result in the expected improvement to mobility, and the state discontinued the program in 2013.
Variable speed limits have not been studied extensively in the United States, so it’s difficult to conclude how effective they are, said Beverly Kuhn, a senior research engineer with the Texas Transportation Institute.
“It’s really not one size fits all,” Kuhn said. “Most of the projects have been very site-specific, and may not have had a very comprehensive, truly objective research analysis of the effectiveness of it.”
Nevertheless, a lot of states are interested in trying them out, Kuhn said.
GDOT officials said the pilot program on I-285 could be expanded to I-75 and I-85 inside the Perimeter one day, if it proves effective.
About the Author
