Exhausting work

If Hong Kong doesn't get the 'carrots and sticks' formula right, it will continue to be hard to replace the old and highly polluting commercial diesel bus and truck fleet. There is no doubt about the harm these vehicles cause. Government data shows they are the principal emitters of roadside pollution, accounting for 88 per cent of the highly health-damaging particulates and 76 per cent of nitrogen dioxide, another pollutant.

Overseas research shows that those living within 500 metres of busy and congested roads are the worst affected. Negative health impacts include asthma, allergies, impaired lung functions in children and cardiovascular problems for the elderly.

Government data also shows how many old clunkers Hong Kong has. Of the 117,000 diesel commercial vehicles under licence, 23,000 date back to before the progressively tighter Euro emission standards were introduced; 15,100 are Euro I, 28,000 Euro II, 31,000 Euro III, 20,000 Euro IV and 150 Euro V. Anything below Euro II are truly awful polluters and should be off the road.

Including the Euro II vehicles, this means 66,100 of the total fleet should be retired. The very worst culprits total 38,100; these pre-Euro and Euro I vehicles generate a staggering 73 per cent of all the particulate emissions of the commercial diesel fleet.

There is no technical argument about what Hong Kong needs to do; the debate is over how to do it. In 2007, the government provided a subsidy scheme for truck owners to replace the pre-Euro and Euro I clunkers, but uptake has been slow. Some say the subsidy is too low, while others say there was no 'stick'.

The government tried to get legislators to increase the vehicle licensing fee but none of the parties were willing to back the measure. Dispirited, environmental officials lost the will to fight.