Quadrant roadway intersection


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 or right turns 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.
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. 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.

Variants

Single-quadrant intersections feature a single quadrant road.
A double-quadrant intersection adds a second quadrant road placed opposite another.
Another variant links grade-separated roads, generally a faster road with denser traffic, to a less traveled, slower road, via the quadrant road. This design is referred to as a one-quadrant interchange or as a single-loop intersection. This type of junction is common in Germany, where it is called a "partial at-grade intersection". A so-called two-quadrant interchange also exists, which adds a second quadrant road.

Examples

Canada

The single-loop variant is used frequently in the Thornhill area, in the Greater Toronto Area in Ontario, Canada, examples include: