§ Lord AVEBURYasked Her Majesty's Government:
What assumptions about income and population growth "and other variables" were made in connection with the road freight forecasts just produced; what are the "other variables" referred to, and what functional relationship is assumed between freight-ton miles and all the independent variables used in the forecast.
§ Lord MOWBRAY and STOURTONThe main assumptions used, including those for the growth of income (GDP per head) and population are set out in Table 7 ofNational Road Traffic Forecasts published by the Department of Transport earlier this month; I am sending the noble Lord a copy. Population growth, as currently projected, is not however assumed to have a significant impact on the demand for road freight. As explained in Appendix II of the publication, forecasts of output and consumption of the different commodities transported are related to the expected growth in gross domestic product. However, account is also taken of past trends and expectations about the development of production, distribution patterns and transport methods for the main groups of commodities. This includes the competitive position of rail for particular traffics and, in the conversion to vehicle mileage, changes in the proportion of traffic carried in the heaviest vehicles. The procedure is not, therefore, described by a mathematical relationship of the sort used to forecast the general growth of car traffic.