I think you should read up on it if you are thinking of running your car on a frosty morning while parked stationery waiting for your windscreen to de-ice!
What about ice cream vans or cement mixers that need to generate electricity while their vehicles are running.
And don’t get me started about the buses and taxis that need to wait!
Seems daft to me!
If you are a driver look up this rule now!
http://www.michaeljohnson.co.uk/?p=1953