The matters of saving travel time, using travel time and valuing travel time have constituted an interest I have actively engaged in researching over the past four years. Presented with the privilege of being one of the reviewers for David Metz's paper, I instantly took a liking to it: for me it harnessed two key strengths, namely that it was prepared to challenge orthodox thinking in a crucial area for the development of transport and society and that it did so in a clear, coherent and accessible way that hopefully encourages a wider constituency of researchers, practitioners and policy-makers to engage in ongoing deliberations around this topic. What is so intriguing and challenging about travel time in terms of policy and appraisal is that a consensus of understanding and interpretation does not exist in the intellectual debate and yet the orthodox accounting for travel time in appraisal, in particular, has endured for some four decades. I had the privilege of convening and reporting upon a workshop in the UK in 2005 which brought together many of the individuals, including Metz, who have engaged in the debate - some subscribing to orthodox thinking and practice; others contesting it. The report sits quietly on the Department for Transport's website, should the reader have an interest in probing further (. gov.uk/pgr/economics/rdg/reportonworkshoptraveltimeus1081). One important point, which has stuck with me, was made at that workshop by John Bates - a staunch contributor to and supporter of current approaches to valuation and appraisal of travel time savings. He expressed his frustration at the misconceptions that prevail in and which hamper the intellectual debate - such misconceptions can distract from being able to identify the truly contestable propositions and arguments. A good example of this, from my own point of view is the following. In UK transport appraisal, travel time during the course of the working day is assumed to be unproductive and thus any saving in travel time results in a conversion of unproductive time into productive time with a unit value based upon wage rates. The misconception in this instance is that appraisal is valuing travel time - which evidence shows increasingly can be used productively (see e.g. Lyons et al., 2007). In fact appraisal is valuing travel time savings - a rather different matter. The contestable proposition then becomes that of whether there is an overlap in practice (at the aggregate) between the proportion of time used productively (fully or partially) on a journey and the proportion of time that could be saved on such a journey if investment in a transport scheme were made.
展开▼
