tag:blogger.com,1999:blog-10939281.post8391487603915552669..comments2024-03-17T08:16:42.227+01:00Comments on World Streets: The Politics of Transport in Cities: Envisioning the Future: 21 Ways to InflateTraffic ForecastsUnknownnoreply@blogger.comBlogger2125tag:blogger.com,1999:blog-10939281.post-22071951261916955242009-04-28T09:43:00.000+02:002009-04-28T09:43:00.000+02:00In the UK, the main problem in regard to forecasti...In the UK, the main problem in regard to forecasting the effects of new roads has been the underestimation, rather the overestimation, of traffic forecasts. Specifically, until recently the Highways Agency refused to recognise the reality of induced demand and even now I feel that its position is that while induced demand can happen it won't happen in respect of the road they are currently Simon Nortonnoreply@blogger.comtag:blogger.com,1999:blog-10939281.post-17510423346111891132009-04-28T09:39:00.000+02:002009-04-28T09:39:00.000+02:00In the UK, the main problem in regard to forecasti...In the UK, the main problem in regard to forecasting the effects of new roads<br />has been the underestimation, rather the overestimation, of traffic forecasts.<br />Specifically, until recently the Highways Agency refused to recognise the reality of induced demand and even now I feel that its position is that while induced demand can happen it won't happen in respect of the road they are<br />In the UK, the main problem in regard to forecasting the effects of new roads has been the underestimation, rather the overestimation, of traffic forecasts. Specifically, until recently the Highways Agency refused to recognise the reality of induced demand and even now I feel that its position is that while induced demand can happen it won't happen in respect of the road they are currently trying to promote. Induced demand often destroys the case for a road in terms of congestion reduction. In an extreme case, demand will rise to match the capacity increase so there is no reduction in congestion on the road in question. In other cases, there may be some relief to congestion on that road but it's offset by an increase in congestion on other roads which the induced traffic will be using on other parts of its journey. It is, therefore, surely not surprising that an agency concerned with building new roads (as well as managing existing ones) will want to downplay the extent of induced traffic. Which leads me to wonder -- how can exaggerating the effects of induced traffic (point 18 in the posting) strengthen the case for building the road ? That is, assuming that the road is being built as part of a traffic management strategy rather than just to make money. I should say that my comments on the UK situation relate to non toll roads -- indeed I am not aware of any toll roads that have been built in the UK since the M6 Toll route north of Birmingham. Simon Nortonnoreply@blogger.com