Saturation of Demand for Daily Travel

Data from successive national travel surveys show that important characteristics of personal daily travel behaviour in Britain are comparatively stable. Over a 35-year period, there has been little change in average travel time, journey frequency, purposes of journeys, and proportion of household income devoted to travel. The one factor that has changed significantly is distance travelled, as people have taken advantage of growing incomes to travel faster, thus gaining access to a greater choice of destinations. However, this growth in distance travelled has now ceased, an outcome which is helpful in relation to concerns about sustainability and the environmental impact of the transport system. The explanation proposed for this cessation of growth is that mobility-based access and choice increase with the square of the speed of travel, whereas the value of additional choice is characterized by diminishing marginal utility. Hence, a saturation of the demand for daily travel is to be expected, a novel conclusion.