Environmental Impact of Freight Signal Priority with Connected Trucks

Sangjun Park,Hesham A Rakha,Kyoungho Ahn

doi:10.3390/su11236819

Abstract

Traffic signal priority is an operational technique employed for the smooth progression of a specific type of vehicle at signalized intersections. Transit signal priority is the most common type of traffic signal priority, and it has been researched extensively. Conversely, the impacts of freight signal priority (FSP) has not been widely investigated. Hence, this study aims to evaluate the energy and environmental impacts of FSP under connected vehicle environment by utilizing a simulation testbed developed for the multi-modal intelligent transportation signal system. The simulation platform consists of VISSIM microscopic traffic simulation software, a signal request messages distributor program, an RSE module, and an Econolite ASC/3 traffic controller emulator. The MOVES model was employed to estimate the vehicle fuel consumption and emissions. The simulation study revealed that the implementation of FSP significantly reduced the fuel consumption and emissions of connected trucks and general passenger cars; the network-wide fuel consumption was reduced by 11.8%, and the CO2, HC, CO, and NOX emissions by 11.8%, 28.3%, 24.8%, and 25.9%, respectively. However, the fuel consumption and emissions of the side-street vehicles increased substantially due to the reduced green signal times on the side streets, especially in the high truck composition scenario.

Highlights

Traffic signal priority is an operational technique employed to ensure the smooth progression of a specific type of vehicle, such as a transit bus, an emergency vehicle, or a freight vehicle, at signalized intersections by retaining green signals or by shortening the time of red signals to have early green signals
For the V/C ratio of 0.85, the freight signal priority (FSP) reduced the fuel consumption, CO2, HC, CO, and NOx emissions in the connected trucks by 25.3%, 25.3%, 28.7%, 22.2%, and 24.3%, respectively. This demonstrates that an increased number of connected trucks in the network would benefit the environmental performance at the V/C ratio of 0.85
The simulation results indicate that the FSP effectively reduced the fuel consumption and emissions in the passenger vehicles along the truck route through traffic signal-controlled intersections compared to the base case scenarios

Summary

Introduction

Traffic signal priority is an operational technique employed to ensure the smooth progression of a specific type of vehicle, such as a transit bus, an emergency vehicle, or a freight vehicle, at signalized intersections by retaining green signals or by shortening the time of red signals to have early green signals. A typical traffic signal priority system is composed of four functional components: Vehicle detection, priority request generation, priority request server, and traffic signal priority control [1]. Transit signal priority (TSP), which is the most common type of traffic signal priority, is implemented to enhance the operational performance of transit bus system, whereas freight signal priority (FSP) provides an early green or a green extension to freight vehicles for enhancing their performance and safety. Many studies have been conducted for the development, logic validation, and impact assessment of efficient TSP logics from the perspective of performance, whereas only a few studies have been performed to investigate the impacts of FSP

Objectives

Results

Discussion

Conclusion