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Motorways (Traffic Flows)

Volume 35: debated on Wednesday 19 January 1983

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asked the Secretary of State for Transport which sections of motorways have average daily traffic flows in excess of their design standards.

As I explained to my hon. Friend the Member for Ashford (Mr. Speed) on 30 April 1982, we no longer work to design standards which are fixed in relation to traffic flows; so I cannot specify the degree of excess flows in the way requested. We recognise that delays can occur when traffic flows reach a certain level, which varies according to local circumstances, and traffic flows can attain these levels for short periods during peak hours on certain sections of MI, M4, M5, M6, M62 and M63.

Bearing in mind the high cost of disruption that repairs of these motorways cause, is any consideration being given in the design of future motorways to extend the design life, which at present is, I understand, about 20 years?

In the current year we have reduced the delays due to motorway repairs. Our current practice is to adopt a design life of 20 years for new bituminous roads and 40 years for new concrete roads. In determining the strength of a road we take into account the level of future traffic, which is always uncertain, and the capital cost of provision. Varying strengths of roads have been monitored over the years by the TRRL and this work provides a good basis for decisions. We are considering the design life criteria, because I believe that it is high time that they were reviewed.

As traffic flows on Britain's motorways have consistently failed to match those projected by her Department's civil servants before construction, will the hon. Lady consider referring these sections of motorway to Sir David Serpell with a requirement that he treat them in exactly the same way as he treated the railway system, and close them down?

The hon. Gentleman is requesting detailed knowledge, for which I must ask him to give me notice. Problems have occurred when flows have been higher than those anticipated 20 or 30 years ago. Where possible, hard shoulders have been strengthened so that they can take running traffic during repair periods. This is already being done. Many new developments that are available through new technology are being carried out very well and efficiently by officials in my Department as well as by many British construction companies, of which we are proud.

When my hon. Friend arranges for surveys to be undertaken on trunk roads and motorways in the west country, will she please ensure that the times and dates upon which the surveys are conducted take proper account of the abnormal seasonal traffic flows to the west country? Will she ensure also that these statistics feature in her deliberations on whether further extensions are necessary?

We shall do that, because no survey is correct unless it views an entire year. Traffic flows in different areas peak at different times.

If design factors are not related to traffic flows, is that why we have at the beginning of the M1, which caters for the Midlands, a motorway network that is continually in a state of repair, with one-lane traffic causing tremendous confusion and accidents?

First, there have not been a tremendous number of accidents, but there have been far more than any of us would like. We must remember that the most southern part of the M1 is the oldest motorway in Britain, having been in use for more than 20 years and therefore requires restrengthening. The two-lane section is being brought up to three-lane standard and three lanes are now open on the southbound section. I assure the hon. Gentleman that where there is great peaking of traffic we can build to the best standard for the costs involved. We do not take traffic flows into account in isolation. We take into account, for example, the cost of widening. A good example is the M4 elevated section, which has extremely high traffic flows. The cost of widening that section would be so prohibitive that it would not make sense.