What is start/stop in a car?

Start/stop (or stop/start!) is a system that turns off the engine when you come to a stop – for example at a set of traffic lights – before restarting the engine when you press the clutch or release the brake. The idea is to save fuel and to reduce emissions produced when the car is idling. A start/stop system may not work if the car's battery isn't sufficiently charged, or if the air conditioning is on a high setting. Cars with start/stop use beefed up batteries and starter motors to make sure that the system works as smoothly as possible.