See also:

Office
...

Switch off the engine during longer stops
Switch off the engine during longer stops, e.g., at traffic lights, railroad crossings or in traffic congestion. Fuel savings are achieved after the vehicle is switched off for only approx. 4 s ...

Note
Children in the vehicle Do not leave children unattended in the vehicle; otherwise, they could endanger themselves and other persons, e.g., by opening the doors. ...