A Forecasting Model for Long Distance Travel in Great Britain

This paper summarizes the work that was carried out on the development of a model to forecast longer distance travel by car, rail, coach and air in Great Britain by British residents. This model examines the effects on long distance travel of possible future developments in transport supply as well as changes in economic, demographic and social factors and a range of policy measures. The forecasts are made to 2030. For the purpose of this paper, long distance travel is defined as trips of 50 miles or more one-way. In addition to the four modes, long distance travel is broken down into five journey purposes: business, commuting, leisure day trips, visiting friends and relatives (VFR) and holiday, and two distance bands: 50 to less than 150 miles, and 150 miles and greater. Air is only considered a relevant mode for trips of 150 miles or more. Thus long distance travel is broken down into 35 categories: 15 for trips between 50 and 150 miles (3 modes by 5 purposes) and 20 for trips 150 miles of more (4 modes by 5 purposes). The forecasting model is a dynamic, elasticity driven system of 35 demand equations as described above. For each of these, demand is defined as person miles and is related to travel costs, travel time and the socioeconomic and demographic characteristics of the population by a set of elasticities. All elasticities vary by purpose and distance band as well as by mode. The model forecasts travel on a per capita basis and uses population projections to determine total travel. A number of input values and parameters are required to calibrate the demand model. These are mainly the base values for demand and the exogenous variables, the elasticities determining the relationships in the model and the drivers used to analyze. The base values for the model are taken from the National Travel Survey (NTS) of Great Britain for the years 2004 to 2006.