The area directly behind the car in front of you where there is very little wind. This effect is much more noticeable in full scale racing, but does still exist in radio controlled cars. However, the effectiveness of tailing the car in front of you is very slim as it would be smarter to just pass it. Next time your driving your full scale car or truck, roll down your window and put your hand behind the mirror. Then move it above the mirror. The area behind the mirror is considered the draft.