Left-turning traffic is directed away from the main intersection, as exemplified by green and blue traffic: Green traffic arrives from the south and wants to turn left/west. Blue traffic arrives from the east and want to turn left/south. Left-turning traffic from the remaining two directions not shown for clarity.
A quadrant roadway intersection adds an additional "quadrant roadway" between two legs of an intersection. This roadway adds two three-way intersections in addition to the original four-way intersection, moving all left turns (in right-hand traffic countries) or right turns (in left-hand traffic countries) from the main intersection. The design is intended to improve traffic flow by reducing signal timing phases from four to two in the main intersection. The design is intended for intersections where large artery routes meet in an area of dense development and high pedestrian volume.[1][2]
Proponents also point to a reduction in places where accidents could occur from vehicles potentially crossing paths, as well as a low development cost compared to roundabouts or the more complex single-point urban interchange designs.[1][3][4] Opponents point to the increase in points where accidents could occur with merging traffic as well as the non-traditional nature of the design, which has the potential to confuse drivers. Opponents also rebut low-cost claims, pointing to right-of-way and construction costs of the quadrant road.[1][3]
A related structure known as a jughandle accomplishes similar traffic movement from a more compact shape.
- ^ a b c Turner-Fairbank Highway Research Center (August 2004). "Signalized Intersections: Informational Guide". ALTERNATIVE INTERSECTION TREATMENTS. United States Department of Transportation. Retrieved 3 January 2010.
- ^ Cooke, Jordan (Mar 24, 2009). "Left turns left out of road redesign". Cary News. Archived from the original on April 10, 2009. Retrieved 3 January 2010.
- ^ a b Hummer, Joseph E. (May 14, 2003). "Moving More Cars Through the Same Space Using Unconventional Intersection Designs" (PDF). NCDOT Traffic Engineering Conference. North Carolina State University. Retrieved 3 January 2010.
- ^ "Quadrant Roadway Intersection vs. Traditional Intersection" (PDF). Community Planning Assn. of Southwest Idaho. Retrieved 3 January 2010.