Efficiency and Safety Evaluation of Unconventional Intersections

The conventional countermeasures such as pre-timed, semi-actuated, and actuated signals, signal coordination systems, multiple left-turn lanes, and intelligent transportation systems are not able to overcome the safety and operational problems of traffic congestion (e.g., delay, fuel consumption, crashes, and pollution) in many urban andsuburban areas. The unconventional designs have therefore attracted engineers’ attention as an alternative to solvethese problems. Two main objectives of the unconventional designs are reducing delay and the number of conflict points. The unconventional alternatives may reduce the number of conflict points by re-routing some left-turns. It is, however, vital to know whether they can improve safety by reducing the number and intensity of traffic conflictsbetween vehicles. This research focuses on evaluating the efficiency and estimating the number and intensity ofconflicts between vehicles (as a surrogate safety measure) for six most common unconventional intersection(unsignalized median U-turn, signalized median U-turn, super street, bowtie, forward jughandle, and reverse jughandle) and three conventional intersection (pre-timed, optimized, and actuated) designs by simulating the realworld traffic information using VISSIM, Synchro and Surrogate Safety Assessment Model (SSAM) software.According to the final results, pre-timed conventional intersection has the worst performance, while unsignalized and signalized median U-turn intersections have the best performance (i.e., lowest average delay, highest averagespeed, and lowest number of conflicts, except their high conflicts’ intensity and their long travelled distances). Furthermore, forward and reverse jughandles are safest designs. In addition, super streets cannot be appropriate design alternatives due to their low average speed, high average delay, and high number of conflicts.

Keywords:

Traffic Simulation , Unconventional Intersections , Traffic Conflicts , Measures of Effectiveness