Four years after Kowloon Motor Bus introduced Hong Kong's first environment-friendly Euro IV buses, it has bought a third to add to it fleet of about 4,000 vehicles.
Green groups are not impressed, saying bus operators should phase out their old, polluting fleets as soon as possible.
KMB is the only operator running Euro IV buses, but rivals are likely to follow soon. Since October, all new heavy diesel vehicles registered in Hong Kong must meet the European Union's Euro IV emission standard.
Euro IV has been in force in the EU since 2005.
Buses are either fitted with catalytic converters or use exhaust gas recirculation to achieve emission reductions. The new bus, expected to start running in April, will be Asia's first to use exhaust gas recirculation.
'KMB has already purchased both types of Euro IV buses for the evaluation of their environmental effects and engine performance,' KMB's operations director, Lui Po-chiu, said. 'We'll continue to explore the latest global bus technologies and adopt new solutions.'