Transport bosses have announced that the £4 million trial of three zero-emissions buses in central London has been a success, reports BBC news.

The buses, which store hydrogen in rooftop cylinders, run on route 25 between Oxford Circus and Ilford and RV1 between Covent Garden and Tower Gateway.

The trial is a joint venture between London Buses, DaimlerChrysler, BP, First and the Energy Saving Trust, set up to improve understanding of how well the technology performs in urban settings.

Involving eight other European cities, the two-year trial is the largest of its kind in the world.

Mike Weston, director of operations for London Buses, said passengers had "appreciated the amazing environmental benefits of fuel cell technology and the quiet, smooth ride the buses offer".

The buses had "excelled in reliability" and been "very popular with passengers," he told the BBC.

The buses will not be ready for widespread use for another decade or so due to the current high costs involved in fuel cell technology.

However Mr Weston remained optimistic, saying the trials were a "positive indication that hydrogen fuel cells could offer an alternative to diesel in the future".