There are good and proper reasons for drivers to switch off the engines of stationary vehicles, instead of leaving them idling for extended periods. Killing the engine, when neither caught in highway jams nor at traffic lights, is good for the environment, for human health and for the vehicle. It saves money too.

Contrary to a common motoring fallacy, it is more fuel-efficient to switch off the engine and restart it instead of letting it idle if the wait is longer than 10 seconds. But old habits die hard. Hence the need for steeper fines for repeat offenders from next month. The National Environment Agency cited worries over pollution and the spike in enforcement cases from more than 3,000 to over 5,000 between 2013 and last year. The agency's focus this time is on repeat offenders who will now face a $100 fine - an increase of $30.

So, if there is everything good to be said for switching off engines, why do drivers prefer to leave their engines running while waiting for passengers, unloading goods, making a phone call in a parking bay or taking a break? Blame it on the two Cs: personal comfort and convenience. While snug in their air-conditioned cabins, they might prefer not to think about those outside who are forced to inhale their vehicles' exhaust.

Children are more vulnerable because their small stature brings them closer to vehicle emissions. Asthmatic children are particularly sensitive to fumes which can affect lung function and trigger airway constriction. No matter how fancy a car, all of them - diesel vehicles in particular - emit fine particles that can harm health when breathed in. Even a short exposure could cause discomfort to asthmatics and the elderly.

Drivers of delivery vans and heavy vehicles, cabbies and other frequent road users should spare a thought for others. Everyone depends on a clean environment to enjoy the use of public spaces.