Superstreet

At a superstreet, all traffic on the side road must turn right, where it can access a U-turn ramp. Traffic on the main road can turn left directly.

A superstreet is a type of road intersection that is a variation of the Michigan left. In this configuration, traffic on the minor road is not permitted to proceed straight across the major road or highway; traffic wishing to turn left or go straight must turn right onto the major road, make a U-turn through the median a short distance away from the intersection and then either go straight or make a right turn when it intersects the other half of the minor street.

This requires four lighted intersections, and most traffic must pass through two of them, but each light has only two phases, greatly increasing average traffic flow; there is no need for numerous left-turn phases where most traffic is waiting for only a few cars to clear the intersection.

Practicality

Superstreets are not very common because it inconveniences traffic on the minor road significantly. The portion of the highway where the superstreet is being built has to be redone. This involves widening the median to make space for cars to make a comfortable u-turn and changing the position of the stoplights. However, superstreets are cheaper than interchanges, and help traffic on the major road.

Benefits

A study showed a 20 percent overall reduction in travel time compared to similar intersections that use conventional traffic designs; intersections experience an average of 46 percent fewer reported automobile collisions – and 63 percent fewer collisions that result in personal injury.

See also

• Continuous-flow intersection
• Diverging diamond interchange
• Hook turn
• Jughandle
• Pittsburgh Left
• Michigan Left

External links

• Federal Highway Administration, Alternative Intersection Treatments - Superstreet Median Crossover
• North Carolina DOT - proposed superstreet in Chapel Hill (note: this project does not include the left turns from the main road)
• Brunswick Beacon article Superstreet considered for U.S. 17
• Google aerial photograph of a Superstreet in Troy, MI, near the Somerset Collection
• Information on two superstreets in San Antonio, including detailed illustrations of the various traffic flows.