GERALD Knox raises the possibility of bringing back electric trams as a clean, green alternative to the motor car (June 29). I'm all for excellent public transport, even though my main way of getting about York is a push bike.

Trams are expensive, though, especially in their infrastructure, and only make economic sense in larger cities. I doubt whether York is big enough.

But there is a lower cost alternative with no exhaust emissions - the trolleybus. What I would like to see is a new type of trolleybus with on-board batteries, and a current collector that can be raised and lowered as it travels.

It would not be restricted to travelling under wires, so could follow diversions and overtake other trolleybuses.

Also, the wires would not need to be raised along the entire route, so there could be gaps at complex junctions and near historic parts of the city where there would understandably be objections to their presence.

In the event of a complete power failure battery power would allow them all to limp home, or at least to somewhere where they are not blocking the traffic.

Alan Robinson,

Lindley Street, Holgate, York.

Updated: 11:13 Wednesday, July 03, 2002