Secretary for the Environment Edward Yau anticipated all pre-Euro and Euro I buses will be retired no later than 2012 and 2015, respectively, while Euro II buses will retire by 2019.

Mr Yau told lawmakers today if all pre-Euro, Euro I and Euro II commercial vehicles including franchised buses are retired, the economic benefit will be about $24.3 billion.

He noted under a franchise requirement promoting wider use of environment friendly buses, bus companies must adopt the latest commercially available and proven environmental technologies when setting specifications for acquiring new buses.

The Government has also been working with the franchised bus companies to have them deploy more environment friendly buses to serve the busiest corridors. Up to December, all franchised buses plying Yee Wo Street, more than 92% of those plying Hennessy Road and Nathan Road, and more than 83% of those plying  Queensway and Des Voeux Road Central already met Euro II or above emission standards.

Different options are being explored to reduce bus emissions, including accelerated replacement of old buses, bus route rationalisation, establishing low emission zones, and assessing the feasibility of retrofitting selective catalytic reduction devices onto Euro II and III buses to reduce their NOx emissions.

The Transport Department is also working with the companies to pursue route cancellations, amalgamations, truncations and frequency reductions to reduce the number of buses on roads, especially those plying busy corridors, to improve road traffic and the environment.