§ Mr. WebbTo ask the Secretary of State for the Environment, Transport and the Regions if he will set out the basis on which he has calculated changes in traffic levels in South Gloucestershire between 1998 and 1999; and if he will make a statement on the differences between the results produced by his methodology and the results arising from the council's automatic traffic counts. [141434]
§ Mr. Hill[holding answer 11 December 2000]: We have not attempted to calculate changes in traffic levels between years. Improvements to the way traffic flows are calculated at a local level means that the overall estimated traffic flow for South Gloucestershire has decreased, however the previous estimates are not on a comparable basis. This does not imply there has been an actual decrease in traffic levels, indeed the change is consistent with increased traffic counts at individual census points; rather it implies that previous estimates of overall traffic flow for South Gloucestershire were overstated.
In previous years traffic flow on road links that crossed a local authority boundary were attributed to the authority in which the traffic count took place. With the advantage of computer based mapping software my statisticians have been able to more accurately attribute traffic flow on such road links to the relevant authorities taking account of the length of road within each authority's boundary. It is clearly fairer and more accurate to end links at an authority boundary so that one authority does not artificially benefit from traffic on a length of road that falls within another authority.
Unfortunately for South Gloucestershire it previously benefited from several high flow links where part of the link lay in a neighbouring authority but the count site was in South Gloucestershire. It further benefited from a number of low flow links where the count was in a neighbouring authority and therefore previously did not affect the estimate for South Gloucestershire.
The traffic flow estimates recorded by the authority are in broad agreement with the traffic flow estimates from my Department's counts. Rather it is the more equitable 153W split of cross boundary links that has led to an estimate for 1999 that is lower than that for 1998. This does not imply that traffic in South Gloucestershire has gone down but that previous estimates are likely to have been too high.