ermine whether these land transport infrastructure requirements are met. Road users (direct and "indirect") are a lot like taxpayers in general, so the finance issue should be what is most publicly palatable to fund required transport infrastructure. There will have to be greater willingness to apply user-pay and commercialisation principles for land transport (especially roads) by public finance/transport authorities and their political masters. INFRASTRUCTURE TO 2030: TELECOM, LAND TRANSPORT, WATER AND ELECTRICITY - ISBN 92-64-02398-4 © OECD 2006 4. KEY FACTORS DRIVING THE FUTURE DEMAND FOR SURFACE TRANSPORT INFRASTRUCTURE 1. Key drivers of future surface transport demand One meta-study of global/regional transport forecasts found that the main factors considered in modelling transport growth are economic growth; population growth; energy prices; and government/environmental policies. 1 Few studies extend this basic forecast set of variables to include income levels; household size; demographic composition; population density; technology (e.g. related to energy efficiency); and regulation. 2 This study develops quantitative forecasts of road and rail infrastructure "new construction" (i.e. net additions to capital stock and maintenance construction to preserve the existing value of capital stock) for the period 2005-30. This is based on an economic framework and methodology similar to that implemented by Fay-Yepes (for the World Bank). 3 The data for the key drivers of GDP growth and population growth come from the World Bank and the United Nations respectively, as highlighted in the OECD background paper prepared for this study. Infrastructure capital stock and new construction model The Fay-Yepes methodology for forecasting infrastructure capital stock and new construction is based on the economic relationship (i.e. elasticity) between infrastructure (road and rail) capital stock and GDP per capita (GDPpc). Growth in GDPPC results in a forecast for road (or rail) capital stock, which can then be transformed i