HC Deb 14 December 1973 vol 866 c224W
Mr. Ford

asked the Secretary of State for Trade and Industry what technical reasons led him to fix the 50 mph speed limit; and, in particular, whether he took into account the position of diesel and petrol injection engines and vehicles designed to cruise at an economic speed of 60 to 70 mph.

Mr. Tom Boardman

The speed limit of 50 mph was selected as one which offered a reasonable saving in fuel consumption by reducing wind resistance, consistent with the performance of the modern motor vehicle. Whilst some vehicles may be designed to provide the maximum efficiency at a speed in excess of 50 mph these form only a very small proportion of the 13 million passenger vehicles currently on the road.