Assessment of operational performance of corridors using Unconventional Arterial Intersection Designs (UAIDs): a case study in Cairo

Unconventional arterial intersection designs (UAIDs) have recently proved to be effective in improving the operational and safety performance of at-grade intersections. Studies have shown that the use of UAIDs is cost-effective and significantly increases capacity and reduces delays. Most of these studies compared the performance of isolated at-grade intersections while only few researches have investigated the effect of the use of UAIDs on a corridor. The objective of this study is the assessment of the UAIDs on improving the operational performance of a congested urban arterial corridor in Cairo, Egypt. The existing corridor includes four signalized intersections which are currently operating using conventional signalized intersections. With the increasing traffic volumes, the arterial has become congested and the operational and safety performance have drastically decreased. The research addresses two types of unconventional intersection designs, Median U-turn (MUT) and Restricted Crossing U-turn (RCUT). In addition, the performance of the UAIDs was compared with the performance of a conventional signalized intersection (CSI) with exclusive protected left-turns treatment. The alternative models were optimized using SYNCHRO with real traffic field data measured along the corridor to obtain the optimum cycle length for each geometric alternative intersection at different time peaks. SIMTRAFFIC was used to run the microsimulation of the optimized models to compar with the existing corridor records using several measures of effectiveness (MOEs). The results showed substantial improvement when implementing the MUT along the corridor; where the average system total delay was reduced by 43% and the system travel time was decreased by 39%. In addition, the average speed of the total system was doubled compared with the current average speed in the selected urban corridor.