A recent Post and Courier article on Bluffton's multilane roundabout asked a very relevant question: "Is Bluffton's roundabout a lesson for Mount Pleasant?" The answer is "yes, it was."
From the beginning, the Coleman Boulevard roundabout design was based on the latest standards and included pavement marking elements the S.C. Department of Transportation later implemented for corrective action in Bluffton. As such, the Coleman Boulevard design already addressed the conditions believed to have caused the crashes that were occurring in Bluffton.
The Mount Pleasant design consultant developed plans for the roundabout at the Coleman Boulevard, Chuck Dawley and Ben Sawyer intersection considering current design standards, engineering and human factors principles, lessons learned from similar roundabouts, and much expert input. The design team and SCDOT staff consulted with a Federal Highway Administration (FHA) expert on roundabouts and intersection safety to ensure both the design and operations were appropriate for Coleman Boulevard. Lessons learned from the Bluffton roundabout and others:
Roundabout design practices have been improved since the Bluffton roundabout was designed over five years ago. There is a now a greater emphasis on forcing the approaching drivers to slow down to match the speed of the drivers in the circle, which provides for safer and more efficient operations. Without changing the geometry of the roundabout, in late 2012 SCDOT implemented pavement marking changes at the Bluffton roundabout, which provide a clearer path for drivers as they enter and navigate the circle.
The enhanced markings alone resulted in a significant crash reduction. More intuitive markings and signage that are standard today provide better guidance to reduce confusion and occurrences of adjacent vehicles crossing paths.
Before-and-after crash data for Bluffton indicate 50 crashes occurred at the roundabout in the 18 months prior the marking modifications. Approximately one year after the modifications, there were only 17 crashes, none of which involved injuries.
Each roundabout is unique: The FHA provides design guidelines for single and multilane roundabouts but also encourages the designer to recognize and consider each intersection's specific conditions.
The Bluffton and Mount Pleasant roundabouts differ significantly, which means that the design team must rely on its experience with other roundabouts, and investigate the performance, problems and corrective measures employed at roundabouts throughout the country.
A very significant factor in the effectiveness and safety of a roundabout is driver education. A comprehensive driver education campaign will take place prior to the opening of the roundabout.
Residents of the Town of Mount Pleasant are no strangers to roundabouts or other improvements that require adaptation. The town has several multilane-roundabouts on its roadways. They carry substantial volumes and operate effectively and safely.
Indeed, the first two modern single-lane roundabouts in the state highway system were constructed in Mount Pleasant over 15 years ago.
Single-lane roundabouts are fully embraced and often requested as an intersection solution by the community.
Will the Coleman Boulevard roundabout take some getting used to? Of course. Will there be crashes because it's new? Possibly, but typical crashes are not severe and should abate after initial driver adaptation.
As such, the Coleman Boulevardmultilane roundabout is a viable improvement that fully realizes the town's vision for Coleman Boulevard.
Ann Edwards Lane
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