You are waiting in the car for someone and the engine is running. Or perhaps it's a van or the school bus. Maybe it doesn't seem worthwhile switching off the engine.
Just let it idle away so you will not have to restart the vehicle again - that also should save fuel.
Buzz! No, wrong answer. Try again.
If you allow the engine of your vehicle to idle, it creates unnecessary air and noise pollution. Not only is this a nuisance, but also it can be hazardous to passers-by.
Furthermore, studies have concluded that when it comes to fuel consumption, turning off your engine for 15 seconds or more ensures you save more fuel than if you had left your motor running.
In some countries like Switzerland, the official policy is to urge drivers to turn off their car engines even at traffic lights. In Japan, unnecessary idling can result in a penalty as high as 100,000 yen (HK$6,700).
An investigation carried out earlier this year by Friends of the Earth pinpointed Kowloon Tong, Kwun Tong and Causeway Bay as the worst areas in terms of 'percentage of vehicles idling'.