This radar-based advance monitors the vehicle ahead and adjusts your speed to help maintain a chosen following distance. On long trips, DISTRONIC PLUS reduces the need to repeatedly adjust the cruise control setting, also making stop-and-go traffic more pleasurable by allowing you to advance with just a flick of the cruise-control stalk.(1) Should the car ahead suddenly slow down or stop, the DISTRONIC Proximity Warning System will issue audible and visual warnings. If the calculated closing speed is too high, the PRE-SAFE Brake system automatically engages up to 40% of available braking power(2) and primes the brakes to deliver full power the moment you step on the brake pedal.(3) And if the brakes have still not been applied within 0.6 seconds of calculated impact, PRE-SAFE Brake will automatically engage them at 100% strength, dramatically reducing collision energy.