Hong Kong's idling engine legislation is perplexing as it is copied (according to an Environmental Protection Department official I spoke to) from the traffic and boat idling ordinance of Toronto, Canada.
It is bewildering because, in 2011, Toronto was officially ranked No 1 city in the world in quality of living and clean air, and Hong Kong was voted one of the most polluted.
It is inexplicable that Hong Kong copies an environmental programme from a city that bears no resemblance to the problems the SAR suffers from.
Interestingly, the three minutes of permitted idling per 60 minutes was reduced in Toronto to just one minute and enforced regardless of the weather.
Hong Kong continues with its three minutes per hour and should the hot weather signal be in effect, then idling for as long as you like is perfectly legal.
So on days when pollutants should be reduced, our Environmental Protection Department allows empty coaches to idle and trucks to bellow noxious fumes into the air so a driver can sleep in his airconditioned cabin.