The open-top double decker is being transformed by the county council as part of a greener way of keeping roads free of overhanging branches.

A tree surgeon using a saw will work from the top of the bus as it drives slowly along the road.

The tree-lopping operative and an assistant will have a buzzer, which can be used to signal the driver to stop while branches are cut back.

"A major advantage of the bus is it will help keep traffic flowing in West Sussex, because it will be easy to overtake," said a county council spokesman.

"At present, cutting back overhanging branches often involves having to introduce traffic management such as stop-go boards or temporary traffic lights.

"Because of the height of the bus, it will also help ensure damage to conventional, passenger-carrying buses from overhanging branches is much less likely."

The tree-cutting bus would also help improve safety for operatives who in the past would have needed hoists or climbing equipment to reach high branches.

The bus, which has had all its seating stripped out and has upper deck safety railings, was the idea of Jonathan Ullmer, a county council maintenance engineer.

County cabinet member for highways and transport Cllr Tex Pemberton said: "It's a marvellously innovative way of tackling overhanging branches, and brings added safety to our roads.

"It is going to save a great deal of time and cost, as well as allowing this vital work to be carried out with the minimum of disruption to motorists.

"Bids for deployment of the bus by district and parish councils can be made by ringing the highways department on 01243 642105."