By LIANG TAO, CRI Correspondent

Hong Kong's Kowloon Motor Bus is hoping a new model of air conditioner will put an end to environmentalists' protests against "freezing" buses.

The "fourth-generation" product, previously fitted only in luxurious sedans, will be used on public transport for the first time when new buses go into service next year.

KMB's principal engineer for bus engineering, Kane Shum Yuet-hung, said the equipment would reduce temperature fluctuation inside the bus and reduce fuel consumption and the emission of pollutants.

He said older types of air conditioner cut off the emission of cold air when the bus gets too cold, and vice versa, so it's either all or none and the fluctuation tends to be bigger.

But the new air conditioner adjusts temperature every 30 seconds and it is never completely switched off.

Maintaining a minimal circulation of cold air helps save up to 23 per cent of energy that is wasted in restarting the machine, and less fuel consumption means less pollution.

At present, nearly 3,000 of its 3,500 air-conditioned vehicles are equipped with so-called third-generation equipment and the rest will be upgraded by the end of next year. Adjustable vents will also be installed in all buses.

Earlier this month, environmental group Green Sense found that 90 per cent of 70 air-conditioned buses it tested had a temperature below 25.5 degrees, with one Citybus vehicle found to be at 15.1 degrees.