Beijing, the capital of China is fitting out 50 of its buses with experimental braking systems that it hopes could cut fuel use by up to 30 percent and help clear its smoggy skies.

The 50 buses in the trial will be fitted with hydraulic hybrid vehicle technology, which absorbs energy released as a vehicle brakes and allows it to be released when they restart or speed up.

It can cut fuel consumption by over 30 percent, and emissions by 20 to 70 percent, it quoted Hu Shenglong, vice president of the manufacturer, Chargeboard Electric Vehicle Co. Ltd., as saying.

The test run would last one to two years, but if it was successful Beijing could add the technology to its whole fleet of 18,000 buses, a municipal official saying.

The move is just one of a series of strategies Beijing is sampling or considering to help clear its smog-laden skies before the 2008 Olympics. It has a trial fuel cell bus plying its roads, and some of its fleet is powered by cleaner gas.

It is also planning to build special networks of high-speed buses in exclusive lanes, to make the vehicles run more efficiently and tempt travelers on to public transport.