Letter: Common sense on a foggy motorway

Sir: Francis Roads (letter, 13 March) points out that motorway speed limit signs in fog are frequently inappropriate because of the delay in revising them. But the nature of fog is that patches of poor visibility drift around too quickly for any warning system to react in time.

Common sense is a more reliable safeguard than warning signs. The big problem is that the normal visual clues drivers use for assessing speed and distance are absent. One way to keep out of trouble is to imagine a brick wall across the carriageway at the limit your visual range and to ask yourself: can I stop before I hit it?

J S EVANS

Chesham, Buckinghamshire