HC Deb 24 July 1974 vol 877 c474W
73. Mr. Percival

asked the Secretary of State for the Environment of he will consider the possibility of fog warning lights being installed at the entrance to all motorway approach roads so as to warn motorists of fog early enough to enable them to take an alternative route instead of the motorway.

Mr. Carmichael

Signs giving warning of fog have been used at motorway entrances. Experience was that difficulties of monitoring fog and knowing when to use the signs made them an unreliable guide to conditions on the motorway.