I was going to send the query to tow, but while its definition is the origin of the expression 'go to slipstream', there is clear association between the bullet out hot air and the "sucking" close to the vehicle going forward to reduce the air resistance e, which improves the relationship between effort and speed.
Slipstream is the tunnel of suction aerorodinamico which generates a car, moped, bicycle or other mechanism when it moves at speed. In other words: a kind of vacuum that breaks the air resistance, allowing who goes back [to slipstream save energy and gain speed, thus, how to get more comfortable in will do if it is bike.] In cycling, it is called commonly known as tailgating.
