§ 32. Mr. Boydenasked the Minister of Transport how much money would be saved each year in the motorway construction programme if gradients of 1 in 15 or of 1 in 12, respectively, were accepted instead of the normal 1 in 30.
§ Mr. MarplesLittle, if any, money would normally be saved by accepting such gradients and it would, in most cases, then be necessary to provide extra "crawler" lanes on the steeper gradients to enable traffic to flow freely. Such gradients would add seriously to the cost of operating commercial vehicles on the motorways.
§ Mr. BoydenDoes not the performance of commercial vehicles in tackling gradients improve every year with advances in manufacturing techniques? Is not the cost of excavating and filling in one of the heavy costs of motorway construction? Has the Minister's Department really studied the matter as authoritatively as he seems to suggest?
§ Mr. MarplesYes, we have studied it authoritatively. We have even been to America to study experience there. The Americans have found that, if there is a gradient of 1 in 15 or 1 in 12, they have to provide a crawler lane which costs £37,000 a mile in one direction. This extra lane is required so that the heavy traffic which goes slowly on the inside lane may be overtaken by other traffic on the outside. Since the heavy traffic goes slowly on a steep gradient, it is necessary to provide this extra lane, and experience in America has shown that it is not worth while. We have studied the matter closely.