HC Deb 14 December 1960 vol 632 c46W
65. Sir L. Ropner

asked the Minister of Transport whether, in view of the fact that, as at present constructed, dual-carriageway roads are very nearly broad enough to take three lanes in each direction, he will give an estimate of the average increase in cost if dual-carriageway roads were designed to carry three lanes instead of two.

Mr. Marples

Experience has shown that for safe and convenient operation with vehicles up to 8 feet wide, each traffic lane needs to be 12 feet wide. To provide three lanes in each direction instead of two would therefore mean increasing the width of each carriageway from 24 feet to 36 feet. The additional cost would vary between about £50,000 and £100,000 per mile according to terrain and the number of bridges.