Hong Kong is recording record air pollution levels this year and is considering a ban on idling engines to reduce roadside pollution.
Hong Kong has thousands of taxis and hundreds of minibuses. They keep their engines running while waiting for passengers in order to maintain their air conditioning.
Temperatures in Hong Kong reached 30 degrees last week.
But the death of an elderly minibus driver in the hot weather has led to professional drivers seeking an exemption to a ban on idling, which could seriously weaken the proposed law.