Changing The Way We Look at Left Turns

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Superstreet (photo courtesy of Dr. Joe Hummer, NCSU)

(Kate Hinds, Transportation Nation)  What kind of traffic design "results in significantly faster travel times, and leads to a drastic reduction in automobile collisions and injuries?"

According to a new study by North Carolina State University, the answer is...a *Superstreet.

These roads, which are also more dryly known as  "restricted crossing U-turns," are streets in which drivers have to make right turns in order to go left (although some do allow direct left turns, like in the photo above).  Doesn't that seem counter intuitive to the "faster travel times" claim? But the NCSU press release addresses this:  "While this may seem time-consuming, the study shows that it actually results in a significant time savings since drivers are not stuck waiting to make left-hand turns or for traffic from cross-streets to go across the thoroughfare."

More importantly: one of the academics behind the study, NCSU civil engineering professor Dr. Joseph Hummer, says: "We also found that superstreet intersections experience an average of 46 percent fewer reported automobile collisions – and 63 percent fewer collisions that result in personal injury.”

Dr. Hummer's team studied collision data from 13 superstreet intersections in North Carolina--making the study "the largest analysis ever performed of the impact of superstreets in real traffic conditions."

There are, of course, caveats. The existing superstreets are mostly in rural areas where there are few pedestrians. And because they're so U-turn based, they require a certain width. But the researchers say that these "unconventional arterial designs...may provide promising solutions."

A paper on the research is being presented next week at the Transportation Research Board annual meeting in Washington, D.C.

You can read more about superstreets in Grist or on the Smithsonian's blog. In the meantime, sing along with me:

*It's a very funky road

The kind you take to see your mother

It will never let you make a left turn

Once you get onto the street

It's a superstreet! Superstreet!

(with apologies to Rick James)

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