Analyzing System Travel Time in Arterial Corridors with Unconventional Designs Using Microscopic Simulation

Abstract

Recent studies have identified the median U-turn (MUT) design as having potential for improving intersection stopped delay at isolated intersections. This study was an effort to quantify the reductions in travel time and other critical traffic operation measures of effectiveness for the MUT and super-street median (SSM) geometric designs over a system of signals compared with the traditional two-way left-turn lane (TWLTL) design. The key function of the MUT design is removal of all left-turn movements at signalized intersections, creating two-phase signal operations and increased progression opportunities. The SSM design allows perfect progression of through traffic in both directions because signals on both sides of the arterial can operate independently. The analysts constructed models of a typical suburban arterial corridor near Detroit, Michigan, in CORSIM according to a fixed external-node coordinate system and fixed origin-destination volumes. These allowed an equitable systemwide comparison of measures of effectiveness between the arterial designs. An analysis of variance determined the importance of arterial geometry related to total system time, average stops per vehicle, and average speed. Results showed that the MUT and SSM designs improved system travel time and average speed compared with the TWLTL design. Analyzing geometry as a function of the time of day showed that the MUT and SSM alternatives significantly reduced system travel time and increased average speeds during the a.m. and p.m. peak hours and showed very similar results compared with the TWLTL design during off-peak conditions. The authors recommend that engineers analyzing alternatives for arterials similar to that tested consider the MUT and SSM designs.