The start-stop system automatically switches off the engine when the car is stopped, for example at traffic lights, and starts it automatically when the journey continues. 

This is how it works: brake the car down to a standstill, shift into neutral and release the clutch. The system now switches off the engine and signals this via an indicator lamp. Depress the clutch before continuing the journey – the engine now starts automatically and the indicator lamp goes out again.

The start-stop function only works when …

• the driver’s door and the bonnet are closed
• the driver is wearing a seat belt
• the vehicle has been driven at faster than 4 km/h before stopping
• the vehicle is not pulling a trailer

In some cases the engine will not be switched off, for instance when …

• the engine temperature is still too low
• the difference between the interior temperature and the temperature selected via the air conditioning system is still too great
• the outside temperature is very high or very low
• the windscreen is being de-iced
• the optional parking aid or the optional park assist is activated
• the battery charge is too low
• the steering wheel is at a sharp angle or is being turned
• reverse gear is engaged
• the road is steep

The engine is started automatically by the system when …

• the vehicle rolls forward
• the windscreen is being de-iced
• there is a large difference between the interior temperature and the temperature selected via the air conditioning system
• the brake pedal has been depressed several times in succession
• the battery charge is too low
• power consumption is too high

Article source: www.audi.co.uk