Today, our community is facing a growing number of transportation challenges, as traffic grows and congestion worsens for signalized intersections. Based on that its needed balances solutions that improve safety and keep mobility for users with minimum travel time. To achieve these goals, a signalized intersection with displaced left turn are worth considering for more getting vehicle through the same spaces than the conventional intersection. Additionally, displaced left turn allows left turning traffic moves simultaneously with traffic resulting in significant operational benefits: saved time, agency saved cost, and communities benefit from safer facilities. The displaced left turn intersection is known also as continuous flow intersection of CFI moves the left turn crossover upstream and compared to conventional intersection conflicts are fewer at DLT and therefore improving intersection safety.
The objective of this research are to investigate the implementation of continuous flow intersection with displaced left turn with developed simulation traffic model by VISSIM program ver.9 to evaluate the traffic operation impacts of displaced left turn on performance of signalized intersection in terms of vehicle delay, length of queue and stopped delay. The results of simulation models for conventional and displaced left turn (DLT) intersections are compared to investigate the effect of high left turn traffic on their operational performance.
The displaced left turn known as continues flow interstation is also an innovative design to improve mobility and safety by changing the direction of left turn on signalized intersection. This improved efficiency by allowing left turn and through movement on one or multiple approaches to occur at the same time and alleviate congestion. The main advantages of DLT interception is to increase the capacity that eliminate the need for future grade-separation intersections and increase the safety to reduce traffic accidents at high location of traffic vehicle crash (FHWA-HRT-09-060).
The authors [1,2,3,4,5,6] stated the adversely impact of U-turning vehicles on the capacity of a signalized intersections, and their obtained results showed an 8% reduction in the capacity for more than 40% of U-turn vehicles of the overall traffic volume [7].
Abdelrahman et al. [8] studied DLT intersections and concluded that DLT minimized delay at intersections and increased crash frequency in comparison to conventional intersections and recommended for safety countermeasures should be implemented to enhanced traffic safety at displaced left turn intersection (DLT).
Otkovic et al. [9] used the neural network to calibrate the VISSIM simulation model and applied the model on selected case study and gave basic insight to the methods of calibration of VISSIM microsimulation traffic for urban transport network. Otherwise, Qu et al. [10] stated that DLT did not increase the crash rate of overall studied intersections and crash rates that are related to left and right turn were reduced significantly.
Findings from previous studies approved that microsimulation traffic software are useful for implementing and evaluating the operational performance of signalized intersection which will be useful for transportation modeling and accommodating the innovative solution for road network for future traffic volumes. The above studies did not adopt the change in traffic regulation for local regions laws and their effect on performance operation and capacity of signalized intersections.