Upstream Signalized Crossover Intersection: An Unconventional Intersection Scheme

The impact of left turns on operation is probably the most significant factor in the performance of conventional intersections. As a result engineers have looked to alternative measures for dealing with left turns at intersections to improve performance, some of which have been unconventional schemes. The purpose of this paper is to discuss an unconventional intersection scheme, the upstream signalized crossover (USC), which is a four-legged intersection designed to eliminate left turn opposing conflicts by crossing the left and through traffic to the left side of the road at all four approaches prior to the intersection. The crisscrossing of traffic upstream of the intersection results in four additional secondary signalized intersections. VISSIM was used to model and analyze the unconventional USC intersection as well as a conventional intersection for comparison. The analysis revealed that the USC intersection can handle higher traffic volumes at reduced overall delays. In terms of left turn delay, the conventional intersection performed better at lower volumes. However, the USC was able to handle much higher left turn volumes while maintaining acceptable level of delay. In terms of through movement delay, the USC intersection was found to perform significantly better than the conventional intersection.