In single seater, open wheel racing series such as Formula One and the IndyCar Series, as well as to a lesser extent in sports car racing, a technique known as "slipstreaming" is used. Along a long straight a car following close behind another uses the slipstream created by the lead car to close the gap between them, hoping to be able to overtake the leader under braking for the next corner, or if he has a straightline speed advantage, to pass on the straight. However it is very difficult for cars to follow each other close together in fast corners as the "dirty" (turbulent) air that comes off the lead car unbalances the trailing car as its aerodynamic devices provide less grip. 4-time Indianapolis 500 winner Rick Mears was quoted by motorsport.com writer David Malsher in 2015 as saying "The fact is, grip created by aerodynamic downforce is our enemy… At the moment, the downforce is so great that it masks the handling and hurts the racing."