Quantifying the Safety Effects of Access Management Using VISSIM and SSAM: A Case Study

Abstract

The purpose of this study is to determine the safety and operational impacts of different levels of access management strategies on vehicular traffic. The researchers concentrated the study on one of the major arterial located in Lawrence, Kansas. This research used VISSIM 5.40 microsimulation software to model the existing conditions and three models with different levels of access management such as low, medium, and high. These models were based on the 23rd Street/ Kansas -10 located in Lawrence, Kansas in 2014. The two access management strategies that were implemented were driveway consolidation and median control. The three levels developed were: 1) low - driveway consolidation only, 2) medium - driveway consolidation along with raised median and 8 mid-block openings, 3) high - driveway consolidation along with raised median and 5 mid-block openings. Left turning movement into the driveways was only permitted at the mid-block openings. Simulated conflict were used to evaluate the safety of the access management strategies. The researchers used Safety Surrogate Assessment Model (SSAM) to identify the simulated conflicts generated by VISSIM. The simulated conflicts and travel times of each model were compared with each other. There was an increase in the travel times for the low level and the high level of access management compared to existing conditions. The medium level of access management experienced a slight decrease in the travel time compared to the existing conditions. In case of total simulated conflicts, there was a significant decrease and a slight decrease in the low level and the medium level respectively when compared with the existing conditions. The total simulated conflicts increased significantly for the high level compared to the existing conditions. There was a significant decrease in the crossing conflicts in all the levels compared to the existing conditions. In conclusion, the findings of this study indicated that the access management strategies do have a positive effect on the safety of the corridor.