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Wind tunnel tests are conducted using l/8th scale models of a standard U.S. mini-van to study the effect of inter-vehicle spacing on the drag of each of the vehicles in 2, 3 & 4-car platoons. The wind tunnel has a ground plane equipped with boundary layer control provided by means of suction over a homogeneously porous surface. Internal, 3-component force sensors are used to measure drag, side force, and yawing moment on each model. Drag coefficient of an individual vehicle alone is about 0.33. When spacing between platoon members is greater than about one vehicle length, the interaction among members is relatively weak. The drag of the lead vehicle is unaffected by the presence of other platoon members; each succeeding vehicle exhibits a lower drag coefficient. For spacings less than 1 vehicle length, drag coefficients are reduced for all members of the platoon, although the interior members experience the greater savings.

Drag measurements are made on each of the members of 2, 3 & 4-vehicle platoons. One-eighth scale vehicle models are used in a wind tunnel equipped with a suction surface ground plane for boundary layer control. Strong interaction between vehicles takes place for spacings less than one vehicle length, leading to drag values substantially lower than for an isolated vehicle. All vehicles in the platoon experience lower drag. The average drag coefficient for a 4-vehicle platoon at a nominal spacing of 0.2 vehicle lengths is just 56 percent of the drag of the vehicle in isolation. It is also concluded that little additional benefit is achieved by forming platoons longer than 6-7 vehicles. Finally, the 2-vehicle platoons are operated in different orientations-front-to-front, back-to-back and reversed-to provide an estimate for drag reduction sensitivity to vehicle shape.