Exhaust policies

The government has just published in the Official Gazette a plan to encourage the scrapping of two-stroke motorcycles. Under the scheme, owners will receive MOP3,500 to remove their vehicles from the streets of Macau.
Two-stroke engines are known to be more polluting than four-stroke engines. This is a general design feature. The fuel combustion is less efficient; they let out more unburned fuel. Until research brings forth more efficient two-stroke engines, it is generally true that equivalent four-stroke engines emit fewer pollutants.
The replacement with more efficient engines may then have a significantly positive impact, provided two conditions are met: the owners adhere to the scheme in sizeable numbers, and the replacement vehicles are, in absolute terms, less polluting.
The success of the policy hinges then on two unknowns – and it is not known if the government has conducted any studies concerning their likelihood. First, it depends upon how many vehicles that are already in fact abandoned or unused, or would be replaced anyway, will be brought in under the scheme. Is there an estimate of the expected impact of the policy regarding the renovation of the stock?
Second, the subsidy may encourage the acquisition of motorcycles with bigger engines. The gains in relative efficiency may be, at least partially, lost if the average engine size increases.
Note that the Administration has tried before, or at least that was the stated purpose, to encourage the renovation of the city’s vehicle stock. It used tax deductions, going up to MOP60,000 to promote the acquisition of new and purportedly more efficient cars. It is possibly not unfair to say, on the face of the apparent changes in the composition of the Macau fleet, that such a scheme proved to be more of an incentive to buy bigger cars than an effective policy tool to reduce car exhaust pollution. It would be interesting to know if an evaluation of the policy was made, and what the conclusions were.
Time will tell if this new policy will achieve its primary objective. The implementation should, therefore, be carefully monitored. Other aspects could be questioned. It is nonetheless a movement in the right direction and, as such, it must be praised. Hopefully, it is a first step, leading to the set up of a more structured policy approach to fighting vehicle pollution – including other types of vehicles and starting with some of the notorious polluters that roll on our streets.