Induced Supply: A Model of Highway Network Expansion at the Microscopic Level

This paper examines the growth of a highway network based on the present and historical conditions of the network, traffic demand, demographic characteristics, project costs, and budget. The effects of expanding a link on its upstream and downstream neighbours, as well as on parallel links, are also considered. Data span two decades and consist of physical attributes of the network, their construction and expansion history, and traffic levels on each of the links. An observation of this research is that the rate of network expansion has decreased over time. The pattern of expansion for each type of highway was found to differ only marginally, indicating that the model estimated is reliable for general use. The models developed here have important implications for planning and forecasting. © The London School of Economics and the University of Bath 2003