Effect of Platooning on Fuel Consumption of Class 8 Vehicles Over a Range of Speeds, Following Distances, and Mass
A research project funded by the Department of Energy evaluated the fuel consumption reduction of a pair of platooned Class 8 tractor-trailers on a test track over a range of highway truck speeds, following distances, and weights that would represent the conditions of driving on public roads. The platooning demonstration system consists of radar systems, Dedicated Short-Range Communication (DSRC) vehicle-to-vehicle (V2V) communications, vehicle braking and torque control interface, cameras and driver displays. The throttle and braking on the rear truck are controlled using a combination of inputs including, but not limited to: radar-measured distance, GPS locations and speeds of both vehicles, lead vehicle wheel-based speed, torque request and braking application. The system does not control lateral position so the trailing truck driver is still responsible for steering, which is a possible source of variation in the tests.
Testing took place at the Continental Tire Proving Grounds in Uvalde, Texas, on an 8.5 mile asphalt oval with several small grade changes rather than a zero grade environment. A series of ten modified SAE Type II J1321 fuel consumption track tests were performed to document the fuel consumption of the two platooned vehicles and a control vehicle at varying steady-state speeds, following distances, and gross vehicle weights (GVWs). The steady-state speeds ranged from 55 mph to 70 mph, the following distances ranged from a 20-ft to 75-ft, and the GVWs were 65K lbs and 80K lbs. All tractors involved had U.S. Environmental Protection Agency (EPA) SmartWay-compliant aerodynamics packages installed, and the trailers were equipped with side skirts. Fuel consumption savings were recorded through methods prescribed in SAE J1321. The effects of vehicle speed, following distance, and GVW on fuel consumption were then analyzed.
- The lead tractor consistently demonstrated an improvement in average fuel consumption reduction as following distance decreased, with results showing 2.7 percent to 5.3 percent fuel savings at a GVW of 65k.
- The trailing vehicle achieved fuel consumption savings ranging from 2.8 percent to 9.7 percent.
- Tests during which the engine cooling fan did not operate achieved savings of 8.4 percent to 9.7 percent.
- "Team" fuel savings, considering the platooned vehicles as one, ranged from 3.7 percent to 6.4 percent, with the best combined result being for 55 mph, 30-ft following distance, and 65k GVW.