§ 98. Mr. John Leeasked the Minister of Transport what is her latest annual estimate of the cost of road traffic congestion; and if she will state on what assumptions this calculation is based.
§ Mr. SwinglerThe Road Research Laboratory estimates that the cost of road traffic congestion in Great Britain in 1965 was of the order of £730 million.
The Road Research Laboratory's estimate is based on the following assumptions.
Total congestion costs are taken to be the difference between total costs at the estimated average speeds of motor traffic under conditions prevailing during the year under review and the total cost at what the Laboratory estimate would be the speeds on existing roads if there were no congestion. For the purpose of this estimate these speeds are assumed to be 25 m.p.h. for urban roads and 40 m.p.h. for rural roads. The calculation takes into account extra vehicle operating costs and the loss of time of the vehicle occupants including an allowance for nonworking time. The values placed on the various items in the equation are currently under review.
A calculation of this kind involves a number of necessarily arbitrary assumptions. For this reason the Road Research Laboratory's periodic estimates only provide an indication of increases in congestion costs. They should not be regarded as an absolute measure of such costs.