Considerable effort is currently being focused on emerging vehicle automation technologies. Engineers are making great strides in improving safety and reliability, but they are also exploring how these new technologies can enhance energy efficiency. This study focuses on the changes in aerodynamic drag associated with coordinated driving scenarios, also known as “platooning.” To draw sound conclusions in simulation or experimental studies where vehicle speed and gaps are controlled and coordinated, it is necessary to have a robust quantitative understanding of the road load changes associated with each vehicle in the platoon. Many variables affect the drag of each vehicle, such as each gap length, vehicle type/size, vehicle order and number of vehicles in the platoon. The effect is generally understood, but there are limited supporting data in the literature from actual test vehicles driving in formation. This study uses a practical approach to quantify road load changes in each vehicle using axle torque sensors to directly measure the load required to maintain steady-state speeds while in different platoon configurations (compared to driving solo). Three test vehicles were used, which varied in size and type: a passenger car, a mid-size SUV, and a full-size pickup truck. A control computer in each vehicle sent commands to the vehicle accelerator input to control the speed and gap based on radar feedback. The final product of the test program is a set of empirical equations that estimate drag changes for two- and three-vehicle platoons at highway speeds (88-112 km/hr) with varying vehicle and platoon configuration parameters.
