Project: Understanding the Limits of Transport Policy C10

Reference: STP 14/5/21

Last update: 31/12/2009 09:24:59


The main objectives are: to identify the factors which affect travel time budgets amongst the individuals and groups comprising a population, to assess whether any secular trend may be expected and to assess the implications of future demographic changes.

An outline will be prepared on how the travel time budget concept and data might be incorporated into transport scheme appraisal, modelling and planning in order to address the implications of constant travel time budgets for the main elements of transport and land use planning policy and the relationship between the two.


There is an implication in the notion of transport policy that substantial improvements could be made to the transport system, given sufficient ingenuity, investment and good will. However, there is increasing evidence that such policy aspirations cannot cope with the desire for ever-increasing mobility, a deep and powerful force in modern society. In densely popoulated countries, there seems no possibility of meeting the demand for unconstrained movement through construction of additional transport infrastructure, since new and longer journeys would quickly fill the extra capacity until congestion equilibrium is re-established. What limits mobility in practice is the time individuals have available for travel. Transport plans need to acknowledge this time constraint as fundamental.

The project will review the relevant literature and gather and analyse the appropriate data. The findings will be synthesised into a coherent report.


Population Ageing Associates Ltd
14 Montpelier Grove, London, NW5 2XD
020 7681 8040

Contract details

Cost to the Department: £17,250.00

Actual start date: 31 December 2002

Actual completion date: 26 June 2003


Travel Time Constraints in Transport Policy
Author: David Metz,
Publication date: 01/06/2003

Summary of results

  1. Average travel time per person has remained broadly constant at about an hour a day for at least the past 30 years, over which period the average distance travelled has increased by over 50%. The average number of trips per person has also held steady, at roughly 1000 per year. It follows that the growth in travel has primarily taken the form of longer journeys at higher average speeds.

    Constant average travel time implies that the benefits, in aggregate, from improvements to the transport system that have the effect of increasing average speeds are taken wholly in the form of greater distances travelled. No benefits are taken in the form of time savings, even if it is convenient to measure the benefits as if they were. The benefits from infrastructure improvements are the benefits from the additional access gained, which people choose in preference to taking the benefits as travel time savings.

    Most of the intended investment in the UK Government's Ten Year Transport Plan has the effect of increasing average speeds. This will increase distances travelled in proportion to the increase in speed within constant average travel time, and will result in increased environmental detriments. Measures to increase the cost of travel will reduce distances travelled, but are likely to be unpopular. An alternative scenario is therefore considered, in which investment is directed towards increasing the quality rather than the speed of journeys.