The construction of roundabouts in The T&D Region is increasing and S.C. Department of Transportation officials say the primary reason is safety.
"Roundabouts are among the top nine proven countermeasures to improve road safety," SCDOT Safety Project Manager Brett McCutcheon said.
There are two roundabouts under construction in Sawyerdale: one at the intersection of S.C. Highway 3 and S.C. Highway 394, and another at S.C. 394 and S.C. 389.
Work began on the two roundabouts on March 16. They are scheduled to be completed on Nov. 30.
A roundabout is a type of intersection that directs both turning and through traffic onto a one-way circular roadway. There are no traffic signals or stop signs in a traffic circle.
Drivers yield at the entry to traffic in the roundabout, then enter the intersection and travel in a counterclockwise fashion before exiting at their desired street.
Unlike the traffic circles of the past, modern roundabouts are typically smaller and have slower speeds. They require entering vehicles to yield to circulating traffic, according to the SCDOT.
McCutcheon said data from the federal highway safety improvement program is used to identify areas in the state with high crash rates that might be helped with a roundabout.
Engineering studies are conducted that take into account crash data as well as traffic counts. All measures are examined to help improve the safety of the specific intersection.
To be considered for a single-lane roundabout, the intersection typically needs to have fewer than 16,000 cars a day passing through it,
McCutcheon said roundabouts may not be the solution for all intersections.
The Sawyerdale intersections are cited as some of the most dangerous in the state.
Over a 7-1/2 year period, the S.C. 3 and S.C. 394 intersection has seen a total of 33 crashes with 31 of the crashes being T-bone or right angle crashes, according to SCDOT.
Over a 7-year period, the S.C. 3 and S.C. 389 intersection has seen a total of 31 crashes, with 27 being T-bone or right angle crashes.
"We have had success in the reduction of T-bone crashes (considered the most serious) with the installation of a roundabout," McCutcheon said.
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SCDOT studies on 12 of its 22 roundabouts has shown a decrease in total crashes by 64 percent and a decrease in injury cashes by 80 percent, McCutcheon said.
Roy Fields, who lives near the S.C. 389 roundabout, says it does not concern him as motorist.
"I think it may cut back on some of the accidents," Fields said. "A lot of people like to slow down and keep going versus stopping. You have to look around a little bit more and pay more attention."
"It will probably save a lot of accidents," he said.
Samuel Leonard, who lives down the road from the intersection, says he does not mind roundabouts.
"I don't find them nerve-racking," he said. "I think it requires more attention and I think that keeps people from having more accidents. I think they are a good thing to have here."
Leonard says at night S.C. 389 is very dark and many motorists need to drive with their high beams on. He is hoping the roundabout will slow motorists down a little bit.
Roundabouts work by reducing the number of "conflict points" in a traditional four-legged intersection from 32 to eight, simplifying vehicle movements (drivers only ever need to merge to their right) and slowing intersection crossings, particularly in the more rural areas where roundabouts are commonly being installed.
Roundabouts also eliminate left turns and the potential to turn across the path of oncoming traffic.
Other controls, including stop signs and traffic signals, are considered less effective when it comes to safety. Signals tend to reduce the severity of crashes but increase the number of collisions overall. Stop signs can improve safety but also dramatically increase delays.
According to the SCDOT, S.C. 45 at S.C 310 near Holly Hill is the only other traffic circle in the T&D Region that’s funded through public dollars.
A roundabout will also be built at S.C. 210 and Cattle Creek Road.
A typical roundabout costs about $700,000 to $800,000. Signals can cost about the same or more and can incur ongoing maintenance costs that roundabouts do not.
Just 20 years ago, there were fewer than 200 roundabouts in the nation, and only one in South Carolina on Hilton Head Island, according to Kittelson & Associates, an engineering firm that maintains a roundabouts database.
Today, there are more than 3,200 nationwide, according to Kittelson.