State could look at boosting speeds on urban interstates
Raising the speed limit on I-285 South has gone so smoothly that state transportation officials are considering doing the same on other metro Atlanta interstates.
After Nov. 1, when the speed along a 27-mile stretch of I-285 South was boosted from 55 mph to 65 mph, average speeds along that corridor barely shifted. In fact, the 24-hour average is a tenth of a mile per hour slower than it was before the change.
The average speed recorded at eight speed detection locations between Nov. 1 and Dec. 31 was 65.4 mph, compared with 65.5 mph before, according to records provided by the Georgia Department of Transportation.
“It was not like everybody started going 10 to 15 mph higher,” said Russell McMurry, the chief engineer for GDOT. “It tells you the speed limit is set at the right limit when you see that kind of reaction.”
Now, GDOT officials are supporting a proposed change in state law to allow maximum speeds of 70 mph on interstates in urban areas, defined as having populations of 50,000 or more.
But don’t hit the accelerator yet.
No interstate speed limits will be automatically raised if House Bill 774 passes, said Joshua Waller, the director of government and legislative relations for GDOT. The proposed law just gives GDOT the option of raising them in areas where doing so could improve traffic flow.
“You will not see a widespread change in speed limits,” Waller said. “But there will be certain areas where, if analysis says it can be raised safely, I think you will see that happen.”
Under Georgia law, interstates in nonurban areas have a maximum speed limit of 70 mph. Urban area speeds are capped at 65 mph.
In metro Atlanta, most interstate speeds are set at 55 mph, based on determinations made by engineers when they are designed and constructed. Those decisions take into account factors such as safety, mobility, efficiency and topography of the road, McMurry said.
Many people who responded to a query on AJC.com’s Facebook page about increasing interstate speeds in the metro area said that drivers are already going faster than posted speeds to keep up with the flow of traffic.
One of them, Morris Devereaux, a 62-year-old retired Fulton County employee who lives in Roswell, said, “I don’t think the signs change anything.”
“The change in speed limit is based on revenue generation, not safety,” Devereaux said. “There have been several studies that show people are going to drive the speed they feel is safe. It doesn’t matter what the speed limit is.”
Chris Groskopf, 38, of Norcross said he supports raising the speed limit “100 percent” and added that variable speed limits should be imposed citywide.
“Common sense says with less traffic you can drive a little bit faster, so just allow us to,” Groskopf said.
A few people, such as Donna Blevins, expressed concern about allowing people to drive faster.
“Most everyone already drives seven to 10 miles above the speed limit anyway,” Blevins said. “Raising it might prompt us to go even faster.”
The change in the maximum speed limit for urbanized areas would bring Georgia in line with many other Southeastern states — including Mississippi, North Carolina, South Carolina and Tennessee — where the maximum speed limits are 70 mph, Waller said.
Exactly which interstate speeds might be altered in metro Atlanta depends on further study. Traffic engineers would look at the current average speeds and examine crash data before making a decision. Areas that make sense to address are those where the population has swelled to above 50,000, but interstate traffic still safely flows at higher speeds.
The concept of boosted speed limits has been used successfully in other cities to help traffic move faster by reducing stop-and-go conditions that can cause crashes.
The next speed limit increase slated for metro Atlanta is on the north side of I-285. In October, electronic variable speed limit signs will be installed along the northern half of the Perimeter. The speed limit there will range from 65 mph downward, depending on congestion.
