The Airport Authority will impose stricter rules on the 2,700-strong fleet of vehicles on the airport island in an effort to reduce emissions. It hopes that within 10 years all vehicles operating within the airport will be clean-diesel, LPG, electric or hybrid-petrol powered. But the authority admits some specialised diesel vehicles might not be convertible, while the reliability of electric cars in airfield operations had yet to be ascertained. To take the lead, the authority is expanding the use of bio-diesel fuel for about 50 vehicles such as passenger buses and operations marshalling cars. It is in talks with Sinopec, which operates three re-fuelling stations in the airport, to ensure a steady bio-diesel supply. At present, the authority relies on a Hong Kong bio-diesel supplier for fuel refined from waste cooking oil. The Environment Bureau is expected to table a bill to regulate the specifications of bio-diesel by the end of this year and the authority expects supply can be expanded once the law is passed. Sinopec is also adapting stations to supply LPG to cars operating within the airport's restricted areas. Besides bio-diesel, the authority has already ordered two My Car vehicles - a Hong Kong-made electric car - for its own use. The cars are scheduled to arrive by October. The authority is in talks with CLP Power to provide charging points for the cars. Deputy director of airport operations, Ng Chi-kee, said there was room to upgrade and replace the airport fleet and cost was not an issue in the project. Of the 2,700 vehicles operating at the airport, about 190 are owned by the Airport Authority and the rest are operated by franchises operating at the airport, such as Hong Kong Airport Services, Jardine Air Terminal Services, Menzies Aviation Group and Hong Kong Air Cargo Terminals. Mr Ng said new contracts would require environmentally friendly or fuel-efficient vehicles be chosen by operators of airport services when old vehicles or equipment were replaced. But the provisions would not specify targets. He said that if all 1,850 diesel-run vehicles were switched to bio-diesel, it could save up to 1,000 tonnes of carbon emissions a year. But Mr Ng also cautioned that any changes must not compromise the safety and efficiency of the airport. 'We can't afford to have an electric car grounded due to a power shortage when it is half way to its destination,' he said 'This might delay the taking off and landing of aircraft.' According to the Environment Bureau's air quality objectives consultation review, if 700 units of ground support equipment at the airport were electrified, it could save 85 tonnes of sulphur dioxide and 759 tonnes of nitrogen oxide. But it said this measure was not as cost-effective as other measures targeting on-road vehicles. The government welcomed the authority's moves to 'green' its fleet with bio-diesel but said the Euro V diesel now on sale at all refilling stations was as clean in terms of improving roadside air quality.