The scheme for diesel commercial vehicle owners to replace their older, more pollutive vehicles with cleaner ones has been extended again.

An initiative to get commercial vehicle owners to replace their older, more pollutive vehicles with cleaner ones has been extended again, the National Environment Agency (NEA) and the Land Transport Authority (LTA) announced yesterday in a statement.

The scheme allows for owners of older commercial vehicles to switch to new vehicles with a discounted prevailing quota premium The Early Turnover Scheme, which was due to end at the end of next month, has been extended to 31 July next year.

Under the scheme, vehicle owners pay a discounted prevailing quota premium - referring to the average of Certificate of Entitlement (COE) premiums over the prior three months - instead of having to bid for a new certificate when replacing their older vehicles with cleaner ones.

The extension aims to give owners of commercial diesel-powered vehicles, which conform to the older Euro 2 and Euro 3 emissions standards, more time to replace their vehicles with Euro 6 models, the statement said.

Such an upgrade would cut tailpipe emissions of particulate matter (PM) and nitrous oxide (NOx) by more than 90% and 60% respectively.

The statement said that while Euro 2 and Euro 3 emissions standards vehicles account for about 30% of the total commercial diesel vehicle population - which currently stands at 135,963 - they contribute almost half of the population's PM and NOx emissions.

Euro 2 and Euro 3 commercial vehicles contribute to high levels of PM and NOx emissions, despite not being the largest population of vehicles However, the statement said the scheme had yielded positive results, noting that as of last month, more than 44,000 vehicles had been replaced with greener alternatives under the scheme. It is the third time the scheme has been extended since it started in 2013.

While newer diesel vehicles are cleaner than older ones, diesel vehicles are still major contributors of PM and NOx pollution in Singapore. "Switching to a non-diesel vehicle can reduce PM and NOx emissions more," the agencies said.

"Dealers are encouraged to introduce cleaner commercial vehicle models to the market for the industry's adoption during the extension. Future turnover schemes, if any, will favour the turnover to cleaner alternatives," they added.

In recent years, the authorities have introduced several measures to encourage the adoption of cleaner vehicles. These include the Vehicular Emissions Scheme, which provides rebates or surcharges on vehicles based on the emission of carbon dioxide as well as four other pollutants - PM, NOx, carbon monoxide and hydrocarbons.

The Vehicular Emissions Scheme, which replaced the earlier Carbon Emissions-based Vehicle Scheme last year, is expected to expire at the end of this year.