§ Mr. SpearingTo ask the Secretary of State for Transport if he will tabulate the maximum design flow in passenger car units per hour of four sections of the M25 motorway between named intersections; and for each sector indicate the measured or estimated recent use, in both volume and intensity, together with the increased additional design capacity he now proposes, together with its respective capital cost.
§ Mr. Chope[holding answer 14 October 1991]: The volumes of traffic that can be carried by a given section of motorway varies according to a number of factors, including the mix of traffic, its distribution throughout the day, the proportions of traffic joining and leaving at junctions and gradients. However a flow of 1,800 vehicles per lane per hour provided a reasonable guide to the maximum unperturbed flow on the existing motorway and a starting point for preliminary designs for widening.
The data requested is not available in terms or passenger car units. The annual average daily traffic flows—AADT—total vehicles in both directions—derived from surveys in 1991 together with the peak hour flows—one direction—for the four sections between junctions 5 and 9 are set out in the table.
Junction AADT Peak hour 5–6 91,000 4,750 6–7 100,000 5,000 7–8 113,000 5,500 8–9 110,000 5,250 The planned addition of a fourth lane on these sections will cost an estimated £5 million per kilometre, including an element for maintenance of the existing carriageways, and will provide for approximately 36,000 more vehicles per day. Additional lanes in the form of collector distributor roads would provide similar additional capacities. Schemes to provide dual two-lane collector distributor roads in the longer term would cost approximately £10 million per kilometre.