Operational and Safety Performance of a Nontraditional Intersection Design: The Superstreet

Abstract

Due to heavy traffic volumes, signalized intersections in many regions across United States are becoming increasingly congested. Operational and safety performance of these intersections have drastically decreased. Alternate intersection designs that may perform better than the conventional signalized intersections are being explored. The results of studies conducted on one non-traditional intersection, the superstreet, are presented in this paper. The superstreet design is similar to the median U-turn design but has some additional features that allow for perfect progression of through traffic on the major road in both directions by preventing the minor road traffic from crossing the major road. Three different cases of superstreet design were studied. For each case, experiments using microscopic traffic simulation were conducted for varying traffic volumes and their performances were compared to the conventional designs. Limited safety evaluation was also carried out for these designs using a surrogate safety assessment tool (SSAM) based on simulation. Simulation results showed that the superstreet design with one U-turn lane outperforms the comparable conventional intersection under high traffic volumes. For the two U-turn lanes case, smaller increase in throughput was observed. SSAM results suggest that the superstreet design with one U-turn lane is safer than the comparable conventional design. For the two U-turn lanes design the superstreet is not safer than the comparable conventional design.