'Superstreet' traffic design boosts travel time, safety

North Carolina State University researchers say that the so-called "superstreet" traffic design results in significantly faster travel times, and leads to a drastic reduction in automobile collisions and injuries.

Superstreets are surface roads, not freeways. It is defined as a thoroughfare where the left-hand turns from side streets are re-routed, as is traffic from side streets that needs to cross the thoroughfare. In both instances, drivers are first required to make a right turn and then make a U-turn around a broad median.

While this may seem time-consuming, the study shows that it actually results in significant timesavings since drivers are not stuck waiting to make left-hand turns or for traffic from cross-streets to go across the thoroughfare.

"The study shows a 20% overall reduction in travel time compared to similar intersections that use conventional traffic designs," said Joe Hummer, one of the researchers who conducted the study.

"We also found that superstreet intersections experience an average of 46% fewer reported automobile collisions - and 63%  fewer collisions that result in personal injury," he said.

The researchers assessed travel time at superstreet intersections as the amount of time it takes a vehicle to pass through an intersection from the moment it reaches the intersection-whether traveling left, right or straight ahead.

The findings will be presented at the Transportation Research Board Annual Meeting in Washington, DC.