An efficient transport system is crucial for the functioning of modern economies. It gives people the possibility to live, work and participate in recreational activities at different locations. And it enables firms to buy inputs from distant producers and to sell their goods at locations different from their production location.
Transport markets are challenging subjects of research. One main reason is the frequently found divergence between the user equilibrium and the social optimum. The divergence is usually due to the presence of negative externalities that travelers impose on each other (recurrent and non-recurrent travel delays, schedule delays, crowding) and on society as a whole (air pollution, noise, accidents). Another reason is the multidimensional character of the choices of individuals and firms that ultimately determine the transportation demand for a given link, time and mode. These include (i) short-run choices concerning the trip making, the timing (scheduling), the mode and the route, but also (ii) medium- and long-run choices concerning vehicle ownership and locational decisions of individuals (residence, workplace) and firms (headquarters, distribution centers, subcontractors). Complexity is further aggravated (among others) by the network structure, scheduled transportation, and the existence of market power of service operators and infrastructure suppliers.
A first theme in the research relates to the optimal design of economic instruments that aim at increasing efficiency in transport markets. These include pricing, infrastructure investments and information provision to travelers. As first-best policies are often not feasible in reality, also second-best policies are defined and benchmarked against the corresponding first-best policies.
A second research focus is the integration of travel-related short-, medium- and long-run decisions in a coherent modeling framework, from a theoretical as well as an empirical perspective. At the core is the explicit modeling of the linkage between short-run decisions on day- specific travel alternatives, medium-run decisions on travel routines, and long-run decisions on housing and work locations, or car ownership. First results show that models taking into account these inter-temporal interdependencies may yield substantially different results than models that ignore them.
Another dominant research theme is the derivation of monetary valuations of travel attributes, which constitute an essential input for cost-benefit analyses of transport policies. Well-known examples are the valuations attached to reductions of travel time and schedule delays and to improvements in reliability and comfort. These can be derived either from stated preference (SP) data that are collected in hypothetical choice experiments or from revealed preference (RP) data that are collected in real-life experiments. The data are analyzed using advanced discrete choice modeling techniques.