The Department for Transport has been using its ‘New Approach to Appraisal’ – NATA for short – for some ten years.  In essence, this attempts a systematic statement of the expected outcomes of any particular investment in the transport system, including but not limited to the outcome of economic cost-benefit analysis. A year ago the Department announced its intention to review and refresh NATA.  The conclusions have now been announced.  The changes proposed are pretty minor.

At the heart of the cost-benefit approach adopted by the Department is the supposition that the main benefit of investment takes the form of time savings to travellers.  This assumption goes back to the 1960s when pioneering studies computed the time-saving benefits from using the newly opened M1 motorway to travel from London to Birmingham, and from commuting to work on London’s new Victoria underground line.  The results of these studies showed decent returns to the investments, and time saving has been the main economic benefit in the Department’s scheme appraisals ever since.

The problem, however, is that average travel time across the population as a whole has remained unchanged over the past 30 years, as I explain in ‘The Limits to Travel’.  It follows that travel time is conserved, not ‘saved’.  The main benefit of investment is in fact increased access to a wider range of destinations.  I put this argument to the Department when they announced the NATA review last year, but received no response.  I’ve just broached the matter again, at the conclusion of the exercise.  Any response will be posted on this blog.