How does the Audi A1's start-stop system function?

I've heard the Audi A1 has a start-stop system but how exactly does it work and how effective is it?

The Audi A1's start-stop system automatically shuts off the engine when the vehicle is at a complete stop, such as at a red light, to save fuel and reduce emissions. It then quickly restarts the engine when the driver releases the brake pedal, allowing for seamless acceleration.

It's a great feature for city driving, as it can reduce fuel consumption and emissions by up to 8%, but it may not be as noticeable on longer trips or highways where the vehicle isn't frequently stopping.