Analysis of Platoon Impacts on Left-Turn Delay at Unsignalized Intersections

Abstract

Traffic platoons created by traffic signals may have impacts on the operations of downstream intersections because they change the arrival pattern and gap distribution of upstream traffic. There’s been a lot of research dealing with platoon effects on operations at signalized intersections, while very limited research has been done for that of unsignalized intersections. This research aims to develop a methodology for analyzing the platoon impacts on major-street left-turn (MSLT) delay at two-way stop-controlled (TWSC) intersections. The main idea is using a microscopic simulation tool to simulate different platoon scenarios in opposing through traffic, then applying 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, making it practical to analyze the platoon effects on MSLT delay. 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. Calibrations of these simulation models based on field data were performed 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, which effectively simplified the large combination of various factors. At last, the two platoon variables and their relationship with MSLT delay change factor were modeled with regression tools. A relationship between the two variables and the delay change factor was established, which indicated a positive effect by upstream platoons on MSLT delay and made it possible to quantify the impacts. The findings in this research could also be used for future research on left turn treatment regarding platoon or signal impacts.