265 1 Extending Transims Technology to an Integrated Multilevel Representation

New approaches are required to analyse very large land-use transportation systems in which millions of people make millions of trips each day. New computer technology has enabled packages that model very large transportation systems. Some of these models are reviewed and it is concluded that the TRANSIMS system developed at Los Alamos National Laboratory has the best combination of desirable characteristics. All the systems reviewed model links and routes at a single level. Land-use transportation systems are generally multilevel, and the paper reviews a number of approaches to developing multilevel networks with links defined at two or more levels. Of these an approach developed in the nineteen seventies using multidimensional networks has many advantages. The possibility of applying the multilevel representation to TRANSIMS is investigated to produce a land-use transportation modelling system that is unconstrained by size. Such systems could usefully be applied to continents such as Europe, where there are no clear boundaries between cities and urban systems.