Formula One tyres bear only a superficial resemblance to a normal road tyre. Whereas the latter has a useful life of up to , the tyres used in Formula One are built to last less than one race distance. The purpose of the tyre determines the compound of the rubber to be used. In extremely wet weather, such as that seen in the 2007 European Grand Prix, the F1 cars are unable to keep up with the safety car in deep standing water due to the risk of aquaplaning. In very wet races, such as the 2011 Canadian Grand Prix, the tyres are unable to provide a safe race due to the amount of water, and so the race can be red flagged. The race is either then stopped permanently, or suspended for any period of time until the cars can race safely again.