Sir – Paul Godwin suggests that a 50mph limit could be applied to all roads apart from motorways to save both money and fuel (Letters, March 19).

A reduction of the national speed limit to 50-60mph ,including motorways (except for public service vehicles) has, at the last count, been recommended by transport experts at The Policy Studies Institute, University College London, Halcrow, Oxford University and the UK Energy Research Council. This has also been supported by the Parliamentary Environmental Audit Committee, not only as the key to a low carbon transport system, but also to bring home to every road user the urgent need to reduce carbon from transport.

The Department for Transport also accepts the desirability of reducing the national speed limit and acknowledge the beneficial knock-on effects. However, such a move is described as as ‘politically impossible’.

Daniel Scharf, Abingdon