The rationale the National Environment Agency gave for setting July 1, 2003, as the cut-off date in its scheme to deregister older motorcycles is that the date was when Singapore adopted Euro 1 type approval standards for new motorcycles (Owners get incentives to deregister older, more pollutive motorcycles; April 7).

However, the fact is that not every motorcycle registered before that date is equally or more polluting than those registered after that date.

The date a motorbike was registered does not indicate the emission standard it complies with.

A motorcycle may have been made before 2003 but may have been sitting in the showroom of a dealership and registered only after that date.

Motorcycles imported to Singapore also tend to be intended for larger markets, like Europe, the United States and Japan. They do not adhere to a single timeline of emission standards adoption or approval.

In fact, some motorbikes may have emission standards that were years ahead of their time.

For example, motorcycles intended for California comply with the state's emission standards, which are known to be two years ahead of the US Environmental Protection Agency's emission standards.

Furthermore, some pre-2003 motorbikes may have technology to offset emissions that post-2003 motorcycles do not have.

For instance, catalytic converters, an exhaust emission control device, are traditionally found on only larger capacity motorcycles, but not on smaller ones.

A motorbike with such a device could have emission standards exceeding another without it.

Hence, it is a broad generalisation to ban motorcycles based on when Singapore adopted the Euro 1 emission standards.

Jason Hui Min Jian