Japan is soliciting opinions on a new proposal by its Ministry of the Environment, which would bring about what is believed to be the world's toughest ever motorcycle emissions regulations.

The initiative forms part of the ministry's drive to reduce emissions causing respiratory ailments and photochemical smog.

Specifically they target marked reductions in nitrogen oxide emissions, from 0.51 g to 0.15 g/km by 2007, and a sharp fall in hydrocarbons, to 0.3-0.5 g/km from the present regulation of 2.93 g/km.

In addition levels of carbon monoxide must fall from 20 g/km to 2.0 g/km by 2007.

The proposed regulations do not cover particulate matter.

Motorcycles must be able to meet the targets under Japan's '15-mode' test procedure, which includes idling, acceleration, and deceleration modes.

Japan's Environmental Administration Bureau estimates that hydrocarbons released from motorcycles driven in Japan account for as much as a fifth of the total hydrocarbon emissions from all motor vehicles.