The New South Wales State Government has scrapped plans to test all vehicles older than four years for 'greenhouse emissions', a main environmental component of the integrated transport strategy, the Sydney Morning Herald (SMH) reported on its website.

The SMH said the state's Roads and Traffic Authority has substiruted a voluntary system targeting pollution-prone cars, including diesel vehicles.

The authority has decided blanket testing is neither cost effective nor necessary, given recent improvements in air quality linked to cleaner fuels and the invention of better pollution-control devices, the SMH said.

Roads and Traffic Authority chief executive Paul Forward told the SMH the scheme to test diesel vehicles would soon be expanded and Sydney-based bus and truck operators would be invited to have their fleets examined.

The newspaper said mandatory testing of all vehicles and an emphasis on diesel vehicles came about after emission figures showed that diesel vehicles accounting for only 5% of the vehicle pool contributed about 70% of damaging pollutants.