Field Testing of Eco-Driving in Virginia Reveals More Than 20 Percent of Fuel Consumption Savings on Certain Rolling-Terrains.

Field Test Used FHWA AV Fleet to Evaluate Fuel Saving of an Eco-Driving Algorithm.

Date Posted

12/17/2021

Maryland, United States

Maryland,

United States

Identifier

2021-B01609

Eco-Drive Experiment on Rolling Terrain for Fuel Consumption Optimization-Summary Report

Summary Information

Eco-drive has been developed to increase vehicle fuel efficiency and improve the sustainability of the entire transportation system within the connected vehicle (CV) paradigm. As additional fuel wastage is a major concern due to the inefficient transformation between kinetic and potential energy, this study proposed an eco-driving algorithm that optimizes fuel consumption on rolling terrains. For this study, a research team out of FHWA's Turner Fairbank Highway Research Center tested and verified newly developed eco-driving algorithms in the field on an innovative connected and automated vehicle (CAV) platform to better understand its performance and enable optimal vehicle control in support of eco-driving. The CAV used in the field experiment is a part of FHWA’s automated vehicle fleet. The results were quantified to estimate fuel saving benefits of eco-drive.

METHODOLOGY

The experiment was conducted on seven rolling roadway segments in Virginia and Maryland, with a total experimental mileage of around 47 miles. The types of terrain varied from mildly rolling to very hilly. Two scenarios were tested in the experiment:

Baseline: The benchmark was regular cruise control with cruising speeds set to corresponding roadway speed limits
Eco-Drive: vehicles were given an optimal speed profile and were controlled in real time to follow recommended speeds.

Experimental data were analyzed at the segment and subsegment level to derive insights into the effectiveness of eco-drive. The subsegment level analysis compared average fuel consumption of baseline and eco-drive runs at each of the seven sites. Understanding of general eco-drive performance was obtained through close examination of vehicle speed, acceleration, brake status, brake percentages, and instantaneous fuel consumption profiles. Linear regression models were built to understand certain roadway attributes that contributed the most to fuel savings.

FINDINGS

The benefit of the proposed eco-drive system ranged from 3.3 percent to 21.2 percent in fuel savings, with the magnitude of the benefit being affected by hill length and slope grade.
Use of the Eco-drive did not increase travel times (mostly within a range of 5 percent with the baseline) as the trajectory planning algorithm was designed to maintain the same level of mobility while improving fuel consumption.
Eco-drive reduced the amount of acceleration, leading to less braking, which leads to more effective transformation between potential and kinetic energy, and thus less additional fuel consumption for the extra kinetic energy.
It was noted that replacing conventional cruise control with the proposed eco-drive system on rolling terrains is beneficial since the conventional constant speed cruise control is fuel inefficient as it applies gas on the uphill segment of the terrain and then brakes on the downhill segment.
Detailed analysis through linear models also revealed the main contributors to the fuel savings potentially obtained from eco-drive. The longer downhill length of the prior subsegment resulted in larger benefits, while uphill length and average slope of the prior subsegment were found to negatively impact fuel savings.