A vehicle's braking system represents a crucial safety component. The more effective the brakes, the shorter the stopping distance from a specific speed. The brakes must be matched to the engine power, vehicle weight and theoretical top speed. For reasons of safety, modern vehicles are fitted with two brake circuits serving diagonally opposite wheels on the two axles. On small and compact models, sufficient stopping power is provided by a combination of disc brakes at the front wheels and drum brakes at the rear. On higher-powered and mid-sized models, Volkswagen uses more powerful, internally ventilated discs at the front as well as fitting disc brakes at the rear too. Today's minimum standard specification for the braking systems in Volkswagen models comprises an anti-lock braking system (ABS), brake servo and electronic brake-force distribution (EBD).