Saturation of Demand for Daily Travel

Abstract

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.

Mobility, access, and choice: a new source of evidence

“…The substantial increases in access achieved by car use at higher speeds, and by longer journey times, compared with the base case (public transport and/or walking for the shorter time), is consistent with the expectation that choice increases approximately with the square of the speed or of the travel time, because what is accessible is defined by a circle whose area is proportional to the square of the speed and/or time. This conclusion is consistent with the proposition that demand for personal daily travel has ceased to grow because needs for mobility-based access and choice have substantially been met (Metz 2010). The hypothesis of demand saturation is, however, a departure from conventional analysis of daily travel behavior and would need further substantiation for it to form the basis of investment decisions.…”

“…The effective development of policy will depend on a deeper understanding of the interaction between transport and land use, between mobility and access. A previous paper took advantage of the National Travel Survey (NTS), a substantial British data set, to illuminate these relationships (Metz 2010). The NTS provides time series data on personal daily travel extending back more than 30 years.…”

Comparison of travel time between private car and public transport in Cape Town

“…The average travel time in Cape Town was, at about 90 minutes in 2013, at the upper end of the global range, which averages around 70 minutes per person per day (Metz 2010;Schafer & Victor 1998). Of greater significance is the discrepancy between modes in Cape Town, with car users travelling at the global average of 70 minutes, but public transport users averaging around 110 minutes (CCT 2013b).…”

Revisiting reference point formation, gains–losses asymmetry and non-linear sensitivities with an emphasis on attribute specific treatment

“…Unfortunately, research into which reference points should be employed is much 130 more limited than the research concerning how actors react to shifts from reference-values. While Kőszegi and Rabin (2006) To some extent, the use of current conditions as a reference point is justified on the basis of 147 the theory of mental Travel Time Budgets (TTB), which can also be extended to a stable mental 148 budget for travel fare expenditure (Gunn, 1981 (Metz, 2010). A possible explanation is that of habit-based travel decisions,…”