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Highway 17: In N.C. study, U-turns don’t diminish safety
By Charles Swenson
“The day of the two-way left-turn lane is drawing to a close,” said Joe Hummer. “People just can’t drive those as safely.”
The debate over restricting median access to left turns isn’t unique to Pawleys Island, where the state Department of Transportation plans to install a raised median next year.
Hummer is an engineering professor who studied highway design and traffic safety for 20 years at North Carolina State University. He now chairs the civil and environmental engineering department at Wayne State University in Detroit.
Among his work is a study of U-turn safety on raised medians for the N.C. Department of Transportation. It found that “many of the typically cited drawbacks to median-oriented designs are not justified. Raised medians may increase U-turns at adjacent intersections, but this was found to have minimal effects on safety and operational performance. Additionally, raised medians are generally safer than [two-way left-turn lanes] on midblock segments.”
The study specifically looked at “problem areas,” but many had no accidents in the three year period.
The Pawleys Island project calls for installing a raised median between Baskervill Drive and Waverly Road that will restrict left turns from all side streets and driveways except the four that will have traffic signals. There will be 16 median breaks to make left or U-turns in the 1.9 mile stretch.
The study of medians that Hummer took part in was completed in 2004, not long after a study of the Highway 17 corridor on Waccamaw Neck identified a raised median as one way to maintain traffic flow in the face of growing volumes. Nothing since then has changed the view that restricting left turns and adding U-turns is a safer option. “Quite the opposite,” Hummer said by phone from Detroit.
But he isn’t surprised that the project has opposition.
“It’s tough to sell safety. Nobody believes they’re going to be the next victim,” Hummer said.
Although not familiar with the Pawleys Island project, his daughter lives outside Charleston and he is familiar with the work done on Highway 17 and Coleman Boulevard in Mount Pleasant. He has also studied the segment of Highway 17 south of Wilmington, N.C., that opponents of the Pawleys Island project cite as the closest example of what S.C. DOT intends.
The projects both limit left turns, but the Wilmington project is known as a “superstreet.” It doesn’t allow any left turns from side streets. Studies Hummer took part in showed it improved traffic flow even as volume grew.
The Wilmington project was built in advance of large-scale residential and commercial development, so there was no impact on existing business by the limited left turns. Nevertheless, the opposition from business owners to the Pawleys Island project is typical of median projects, Hummer said.
“That’s a tough case. One road’s trying to do two jobs,” he said of Highway 17’s role carrying through traffic and local traffic. “To business owners, I would say I understand the concern, but with a well-designed median – the median openings in the right places, signalized U-turns in the right places – we get both objectives being fulfilled.”
“The devil’s in the details,” he added.
There are ways to gauge the impact of a median project. “One of the best ways to tell is through simulation or animation,” Hummer said. “Watch cars and trucks driving through it, at least on the computer. That can often help alleviate these concerns.”