Standing Advisory Committee on Trunk Road Assessment (Hansard, 19 December 1994)

§ Dr. Mawhinney

I am today publishing SACTRA's report and, following the normal practice with such reports, a full Government response. I am very grateful to SACTRA for the comprehensive and detailed work it has done in this difficult area. Copies of its report and the Government response, together with a brief summary, have been placed in the Library of the House.

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SACTRA was asked to report on traffic generation because the Department recognised that, as economic growth over the last 15 years has greatly increased traffic levels, the number of congested areas has gone up and with them, the cases where a road scheme might bring costs as well as benefits. There was also a growing feeling that there should be a more general examination of whether roads do to some degree increase traffic as well as relieve congestion.

SACTRA has made the case for taking greater account of changes to the origin, destination and timing of existing trips, particularly when projecting traffic flows for road schemes in places where the road network is already congested. Although the report is consistent with our long-standing view that new schemes do not generate a significant number of trips which are entirely new, the overall amount of traffic on the network may in some cases rise by more than is usually allowed for under current appraisal methods.

The Department accepts this and is now looking at all national road schemes in the planning stages, to see if the changes in traffic considered by SACTRA are likely to be significant. If they are, the best means currently available for identifying possible changes in traffic patterns will be applied.

This work will be done with all speed. There is no reason to require or expect delay to road schemes or public inquiries. The important task is to ensure that, for those cases where extra traffic might adversely affect the cost-benefit justification, new traffic modelling is done so that the results can be examined.

However, some of SACTRA's work is not conclusive. There is insufficient evidence to support any simple rule governing the relationship between the amount of time saved on a journey and the use of that time on more travel.

It is clear that a great deal of research needs to be done to develop improved traffic modelling techniques for use in congested conditions. Additional research is already under way, and more will now be commissioned.

I have also been studying the recommendations that SACTRA made on strategic, economic and environmental appraisal and traffic modelling. SACTRA shows the way forward, but it recognises that further studies need to be undertaken before these recommendations could be put into practice. My Department will therefore be developing and testing new techniques in these areas.

I am determined that important, and often very difficult, decisions on road schemes are taken on the basis of the best and most up-to-date methods for forecasting their effects. SACTRA has made a valuable contribution to advancing our understanding of these issues.