§ Mr. SpearingTo ask the Secretary of State for Transport what were the design free flows in passenger car units per hour for each section of the M25 motorway, other than the Dartford crossings and their approaches, and the related increase in design flow for those sections for which widening of that road has already been programmed, or placed in the first phase; and if he will list the approximate capital cost for that widening and associated approach road works for each increase of 100 passenger car units per hour, together with any cost benefit calculations made in respect of any such increase.
§ Mr. KeyThe design flow for a section of motorway will vary depending on factors such as the mix of traffic, its distribution throughout the day, the proportions of traffic joining or leaving at junctions and gradients. However, a level of 1,800 vehicles per lane per hour can be taken as a resonable average value and a suitable starting point for design. Figures in passenger car units are not available.
M25 traffic flows between junctions 12 and 16 (1991) Average weekday 16 hour Average weekday 24 hour Maximum peak hour North hound South bound North bound South bound North bound South bound Junction 12–13 71,800 73,100 72,100 73,600 7,500 7,100 Junction 13–14 78,600 79,200 79,300 80,300 8,300 8,100 Junction 14–15 72,900 74,000 74,300 75,600 6,800 6,700 Junction 15–16 69,600 68,600 74,300 73,700 6,100 6,200 The sections between junctions 12 and 15 are dual four lanes and the section between junctions 15 and 16 is dual three lanes.