Transportation Research Record: Journal of the Transportation Research Board

• Authored by:  F. Wan
• Co-authored by:  Y. Zhang , Kay Fitzpatrick

Wan, F., Y. Zhang and K. Fitzpatrick, “Analysis of Platoon Impacts on Left-Turn Delay at Unsignalized Intersections,” Transportation Research Record: Journal of the Transportation Research Board, No. 2223, Transportation Research Board of the National Academies, Washington, D.C. (2011)

      This research aimed to develop a methodology for analyzing the platoon impacts on major-street left-turn (MSLT) delay at two-way stop-controlled intersections. The idea was to use a microscopic simulation tool to simulate different platoon scenarios in opposing through traffic and then to apply regression models to capture the impacts of platoons on the delay of MSLT. Two platoon variables were adopted as a simplification of the complex platoon scenarios to make analysis of the platoon effects on MSLT delay practical. The first two steps were to build simulation models for real-world unsignalized intersections and simulate scenarios with a combination of various factors related to platoons in VISSIM simulation. The models were calibrated with field data before simulation started. The next step was to define, derive, and calibrate two platoon variables for describing the duration and intensity of platoon arrivals in the opposing through traffic.

      This process effectively simplified the large combination of various factors. Finally, the two platoon variables and their relationship with the change factor of MSLT delay were modeled with regression tools. A relationship between the two variables and the delay change factor was established. The relationship indicated a positive effect by upstream platoons on MSLT delay and made it possible to quantify the impacts. Key findings were:

• For two-lane TWSC unsignalized intersections, there were no evident impacts on MSLT delay by platoons in opposing through traffic generated from the upstream signalized intersection.
• For four-lane TWSC unsignalized intersections, the platoons have shown a positive effect on left-turn delay, which reduces the left-turn delay. Furthermore, as the intensity of the platoon goes up, the positive effect gets stronger and the delay saving percentage increases. The platoon impact can be quantified by using the methodology proposed in this research.

The findings in this research could be used for research on platoon or signal impacts on left-turn treatments.