Superstreet
Encyclopedia
Michigan left
A Michigan left is an at-grade intersection design which replaces each left turn with a permutation of a U-turn and a right turn. The design was given the name due to its frequent use along Michigan roads and highways since the late 1960s. In other contexts, the intersection is called a median...
. 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 interchangeDiverging diamond interchangeA diverging diamond interchange is a rare form of diamond interchange in which the two directions of traffic on the non-freeway road cross to the opposite side on both sides of the bridge at the freeway. It is unusual in that it requires traffic on the freeway overpass to briefly drive on the...
- Hook turnHook turnA hook turn is a traffic-control mechanism where cars that would normally have to turn across oncoming traffic are made to turn across all lanes of traffic instead....
- JughandleJughandleA jughandle is a type of ramp or slip road that changes the way traffic turns left at at-grade intersections. Instead of a standard left turn being made from the left lane, left-turning traffic uses a ramp on the right side of the road...
- Pittsburgh LeftPittsburgh LeftThe Pittsburgh left is a colloquial term for the driving practice of the first left-turning vehicle taking precedence over vehicles going straight through an intersection, associated with the Pittsburgh, Pennsylvania area. The practice is also referred to as a Boston left...
- Michigan LeftMichigan leftA Michigan left is an at-grade intersection design which replaces each left turn with a permutation of a U-turn and a right turn. The design was given the name due to its frequent use along Michigan roads and highways since the late 1960s. In other contexts, the intersection is called a median...
External links
- Federal Highway AdministrationFederal Highway AdministrationThe Federal Highway Administration is a division of the United States Department of Transportation that specializes in highway transportation. The agency's major activities are grouped into two "programs," the Federal-aid Highway Program and the Federal Lands Highway Program...
, 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, MITroy, MichiganTroy is a city in Oakland County in the U.S. state of Michigan, and is a suburb of Detroit. The population was 80,980 at the 2010 census, making it the 11th-largest city in Michigan by population, and the largest city in Oakland County...
, near the Somerset CollectionSomerset CollectionSomerset Collection is an upscale super-regional shopping mall, with over 180 stores located in a Metro Detroit commercial area on 2800 W. Big Beaver Rd. in Troy, Michigan... - Information on two superstreets in San Antonio, including detailed illustrations of the various traffic flows.