The government has signalled its acceptance of yet another exemption to the engine-idling ban - school coaches.
The exemption would apply to more than 1,000 such vehicles, but would not apply to those with fewer than 17 seats - meaning the many minibuses that serve schools would still be banned from idling their engines. That was unfair, some lawmakers said.
Carlson Chan Ka-shun, deputy director of environmental protection, said that if there were general agreement from lawmakers on the exemption he would ask the Department of Justice to draft an amendment to the proposed law.
The new exemption would allow coaches to keep the engine on so as to run the air conditioner, as long as there was at least one person on board.
Miriam Lau Kin-yee, a Liberal Party legislator who represents the transport and logistics industry, said: 'I can't see the logic of why there should be different treatments for school buses of different sizes. This is unfair.'
Chan said officials were concerned that any further exemption would conflict with the goal of improving roadside air quality around schools and frustrate efforts to persuade parents to switch off engines.
'It will have a health impact on those who most need better protection from air pollution if we extend this exemption to buses with 16 or fewer seats,' he said.
At a meeting of the subcommittee discussing the proposed idling ban, lawmakers also pressed the government to widen an exemption for minibuses in a queue to allow the first three to keep their engines running, rather than just two.
But Chan said this would render the law useless at minibus stands, particularly those for red-topped minibuses in Mong Kok. He said it would deprive pedestrians of a minimal improvement to roadside air quality and disappoint vendors and shoppers who were suffering from vehicle fumes at street level.
The government has already made several concessions since it tabled the proposed legislation to ban idling engines and impose a fixed penalty of HK$450 for breaches.
Earlier, environmental officials bowed to pressure from the taxi trade by agreeing to consider exempting all cabs at designated stands, triggering calls from minibus operators for similar treatment.
Other concessions include suspending enforcement after warnings of rainstorms and very hot weather.
After public consultation, the government also introduced to the draft legislation a three-minute grace period to all vehicles.
Meanwhile, the Labour Department said that occupational safety laws did not apply.
Lawmakers had said that vehicles were professional drivers' workplaces, and therefore should be subject to protection. They were concerned about dangerous heat in cars without air conditioning.
Erika Hui Lam Yin-ming, deputy commissioner for labour, said the safety law could not apply, for reasons of important legal principles - though she did not specify these.
Concessions so far
Three-minute grace period for all vehicles
Suspension of ban during rainstorm and hot-weather warnings
All taxis at a designated taxi rank
Any taxi moving into a taxi stand. The first two minibuses at a minibus stand. Any red minibus with a passenger aboard, plus the next bus
School buses with capacity for more than 16