The fuel efficiency improvement of a prototype Driver-Assistive-Truck-Platooning (DATP) system was evaluated using Computational Fluid Dynamics (CFD). The DATP system uses a combination of radar and GPS, integrated active safety systems, and V2V communications to enable regulation of the longitudinal distance between pairs of trucks without acceleration input from the driver in the following truck(s). The V2V linking of active safety systems and synchronized braking promotes increased safety of close following trucks while improving their fuel economy. Vehicle configuration, speed, and separation distance are considered. The objectives of the CFD analysis are to optimize the target separation distance and to determine the overall drag reduction of the platoon. This reduction directly results in fuel economy gains for all cooperating vehicles.In order to correlate the computational studies, fuel consumption tests were conducted conforming to the (1986) SAE J1321 Type II - Fuel Consumption standard using a pair of trucks. Testing was performed using the DATP system at separation distances of: 30ft, 40ft, 50ft, 75ft, and 150ft. These distances were chosen to validate the predicted trend between vehicle separation and drag reduction. Preliminary results from the CFD analysis are presented in this paper. Initial findings suggest that the fuel economy of vehicles significantly improves at diminishing separation distances. Effects at larger distances, as well as the effect of lateral offset, are also presented.