Sir – I’m grateful to Martin Smith (Letters, March 26) for joining me in recognizing that we cannot continue polluting the centre of Oxford with diesel emissions.

However, I’m sad he considers the historic architecture of our city less worthy of protection than that of cities in France.

Regarding the cost of laying APS (and so avoiding an overhead cable), only the centre of Oxford would need such investment.

It is surely possible to construct vehicles capable of acquiring power from both above and below.

Admittedly, this would increase vehicle cost, but it would reduce track cost dramatically.

We should also remember that the current ‘track’ cost for buses is mostly met out of general taxation, and is both large and recurrent. The cost of light rail infrastructure is a capital one, which could be repaid over a century.

Batteries might carry a tram across the centre but would defeat efficiency as they add significant weight to the vehicle over the entire journey. (Even Brunel knew that removing the power supply from the vehicle is key to efficient transport.) Trolley-buses would remove pollution from the city-centre but would force an overhead cable everywhere, and would not remove the threat posed to both pedestrian and cyclist.

I’m sure Martin is also aware that they miss one critical advantage of any train — the greater capacity and efficiency afforded by connecting carriages together.

This allows greater occupancy and also a narrower vehicle, leaving enough space for (safely separated) footpath and cycle-way.

I can but hope I live to see the noisy, filthy, dangerous, stupidity that is the diesel bus give way to the silent sophistication that Oxford, of all places, so richly deserves.

Dr Ian East, Islip