The electronic differential lock (EDL) permits smooth, comfortable starts on road surfaces that do not have a uniform coefficient of friction. If a wheel starts to spin, EDL brakes it as necessary so that power is transmitted to the wheel with the better traction. EDL reduces tire wear and works up to about 40 km/h (quattro® : up to about 80 km/h). EDL is part of the electronic stabilization program (ESP) and the traction control (ASR) .