Microsimulation of Energy and Flow Effects from Optimal Automated Driving in Mixed Traffic

TL;DR

This study uses microsimulation to evaluate how an anticipative cruise controller in automated vehicles can improve traffic capacity and energy efficiency across various traffic demand levels and vehicle types.

Contribution

It introduces a novel anticipative cruise controller with probabilistic safety constraints and analyzes its impact on traffic flow and energy efficiency in mixed traffic scenarios.

Findings

Network capacity improves with automated vehicles at high demand.

Automated vehicles increase energy efficiency by 10-20% for conventional powertrains.

Traffic smoothing benefits energy efficiency of human-driven vehicles.

Abstract

This paper studies the energy and traffic impact of a proposed Anticipative Cruise Controller in a PTV VISSIM microsimulation environment. We dissect our controller into two parts: 1. the anticipative mode, more immediately beneficial when automated vehicle fleet penetration is low, and 2. the connected mode, beneficial in coordinated car-following scenarios and high automated vehicle penetrations appropriate for autonomous vehicle specific applications. Probabilistic constraints handle safety considerations, and vehicle constraints for acceleration capabilities are expressed through the use of powertrain maps. Real traffic scenarios are then modeled using time headway distributions from traffic data. To study impact over a range of demands, we vary input vehicle volume from low to high and then vary automated vehicle penetration from low to high. When examining all-human driving scenarios, network capacity failed to meet demand in high-volume scenarios, such as rush-hour traffic. We further find that with automated vehicles introduced which utilize probabilistic constraints to balance safety and traffic compactness, network capacity was improved to support the high-volume scenarios. Finally, we examine energy efficiencies of the fleet for conventional, electric, and hybrid vehicles. We find that automated vehicles perform at a 10% - 20% higher energy efficiency over human drivers when considering conventional powertrains, and find that automated vehicles perform at a 3% - 9% higher energy efficiency over human drivers when considering electric and hybrid powertrains. Due to secondary effects of smoothing traffic flow, energy benefits also apply to human-driven vehicles that interact with automated ones. Such simulated humans were found to drive up to 10% more energy-efficiently than they did in the baseline all-human scenario.