The government has hammered out a revised HK$10 billion-plus scheme with beefed-up subsidies to get fleet operators to phase out pre-Euro IV commercial diesel vehicles.
The scheme will be tabled to the legislature for discussion on October 2.
Transport sources said the Environment Bureau would increase not just the amount of subsidies given to the operators but also improve how the subsidies were granted.
They said that under the revised scheme there would no longer be a distinction between operators who wanted to scrap their vehicles and those who wanted to replace them.
Both are expected to get the same subsidy, depending on the emissions standards of their vehicles.
The maximum subsidy also might be increased from 30 per cent to up to 40 per cent of the vehicle's replacement cost.
But questions have been raised in the trade as to whether the government might have to seek extra funding from the legislature to implement the revised plan.
At least one person familiar with the situation said extra funds would be needed, but not a significant amount. He said the top-up required might be around 10 per cent.
Another concern was whether the bureau would extend the timetable for phasing out the vehicles in three phases.
It is understood the bureau might postpone the deadlines by one year to 2017, 2018 and 2020.
Undersecretary for the Environment Christine Loh Kung-wai has said the plan for the multibillion-dollar scheme has been finalised, but she did not reveal details.
The scheme, described by Loh as the "biggest of its kind in the world", aims to phase out more than 80,000 commercial diesel vehicles, excluding franchised buses, in three stages, depending on their emissions standards.
Operators of old vehicles whose emissions are regarded by World Health Organisation as carcinogenic will not be allowed to renew their licences once the deadlines pass.
Since the scheme was announced, some in the trade have questioned whether the proposed incentives are adequate and fair. Some operators said the scheme was unattractive as they could not afford to buy a new vehicle, even with the subsidy.
Leung Kun-kuen, of the Kowloon Truck Merchants Association, said that from what he had heard about the revised scheme, the association would "cautiously accept" it.
"There is still uncertainty as to when the scheme will be implemented, as manufacturers have found it difficult to adjust to fluctuations in demand for new vehicles," he said.
Yuen Cheung-fung, of the Federation of Trade Unions, said individual operators were concerned whether they could continue to make a living. He said the revised scheme could partly address their concerns.