Author: Tang Ming Chung, Kelvin, LLB IV; HKU Date: 11/8/10

The drafting of legislation against idling engines is in progress. In recent years, the number of complaints against idling vehicles has been increasing (almost doubled from 238 in 2002 to 501 in 2006). (1) The Government’s publicity and education programmes have been considered insufficient in changing the habits of drivers, and further measures are now proposed to combat the problem instead of relying on education solely. (1)

Nitrogen Oxides Particulates



Private Car Two times more



23% more 25% more
Diesel Taxi 26% more Four times more 40% more

One and a half

times more

Diesel Light Bus Double Four times more Double

Three and a half

times more

Heavy Goods Vehicles Double 13 times more Double Four times more

But due to practical and operational needs, some vehicles may need to be exempted and leave their engines running whilst waiting. (1) Exemptions were proposed for: taxi operators, who need to move taxis forward all the time and switching off and restarting engines frequently would result in higher emissions; public light buses for similar reasons, though it was proposed that only the first few waiting in the queue should be exempted; and school bus operators, many of whom have already been asked to switch off engines by the schools. (1)

Having considered operational needs, the impact on mitigating environmental nuisance, and enforcement practicability, the exemptions have been revised to cover: the first five taxis at a taxi stand; the first two public light buses with one or more passengers on board at a public light bus stand; and coaches with one or more passengers on board. (3) However, the transport sector has urged that the ban should not proceed unless support facilities, such as subsidies for installation of separate air-conditioning systems, provision of shades and covers for taxi stands, and so on, are put in place. (3)

Controlling idling engines will reduce the nuisance caused by their exhaust and heat emissions to nearby pedestrians and residents. However, implementing such control may not necessarily help to improve air quality. If a total ban is imposed on idling engines, some motor drivers, due to operational needs or in order to maintain the air conditioning in the hot weather, may choose to circulate on the road instead of switching off their engines. Under such a situation, not only would the traffic problem worsen, more emissions would be produced by vehicles. (2)

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