Japan has begun conducting tests to ascertain the levels of vehicle tailpipe emissions for nitrogen oxides (NOx), sulphur oxides (SOx), and particulate matter (PM).

According to the Association for Emissions Control by Catalyst the testing is likely to pave the way for tougher auto emission standards to be instituted in 2005.

Under the present Japanese auto emission system, motor vehicles off the assembly line must comply with emission standards for NOx, SOx, hydrocarbons (HC), and carbon monoxide (CO), but once registered they only need to meet HC and CO emission standards.

However, under the new inspections, which are currently operating 'on an experimental basis', vehicles will be tested on the road.

Both commercial and private vehicles will be tested, as well as both petrol and diesel powered machines.