That was usurped for 2011 by the new DRS (Drag Reduction System) rear wing system. This too allows drivers to make adjustments, but the system's availability is electronically governed – originally it could be used at any time in practice and qualifying (unless a driver is on wet-weather tyres), but during the race, it could only be activated when a driver is less than one second behind another car at pre-determined points on the track. (From 2013 DRS is available only at the pre-determined points during all sessions). The system is then deactivated once the driver brakes. The system "stalls" the rear wing by opening a flap, which leaves a 50 mm horizontal gap in the wing, thus massively reducing drag and allowing higher top speeds. However, this also reduces downforce so it is normally used on long straight track sections or sections which do not require high downforce. The system was introduced to promote more overtaking and is often the reason for overtaking on straights or at the end of straights where overtaking is encouraged in the following corner(s). However, the reception of the DRS system has differed among drivers, fans, and specialists. Returning Formula 1 driver Robert Kubica has been quoted of saying he "has not seen any overtaking moves in Formula 1 for two years", suggesting that the DRS is an unnatural way to pass cars on the track as it does not actually require driver skill to successfully overtake a competitor, therefore, it would not be overtaking.