We thank Mr Francis Cheng for his feedback on emissions testing for vehicles ("Vehicle emission checks at inspection centres do not mimic on-road use"; Forum Online, May 8).

The National Environment Agency (NEA) sets the exhaust emission standards for all motor vehicles, which are stipulated in the Environmental Protection and Management (Vehicular Emissions) Regulations.

Under the Road Traffic Act, all motor vehicles are required to undergo periodic inspection at stipulated frequencies, based on their vehicle type. The frequency of inspection generally increases for older vehicles and those with higher mileage.

This is to ensure that such vehicles continue to be road-worthy and their emissions kept in check.

Taxis, given their higher mileage, have higher inspection frequency of once every six months compared with cars which are inspected biennially, from the third till the 10th year.

For vehicles more than 10 years old, the inspection frequency is increased from biennially to annually for cars and from annually to once every six months for goods vehicles and buses.

Tests on exhaust emissions are carried out during the periodic inspections, according to NEA's standards.

As highlighted by Mr Cheng, there are gaps between real driving emissions and testing in laboratories.

The European Union (EU) is updating the procedures for measuring emissions to better reflect real-world driving conditions.

The EU will be introducing the Real Driving Emissions (RDE) test next year for type-approval of new vehicles, which would be more representative of real-world driving and the test procedures would be more robust.

NEA is closely monitoring developments in Europe and will look into tightening our emissions testing regime for both new and in-use vehicles in Singapore.

Fong Peng Keong

Director, Pollution Control Department

National Environment Agency