A parametric description of cities for the normative analysis of transport systems

Abstract

Urban transport systems analysis requires some explicit or implicit representation of the network, activity pattern and flows pattern of the city. When dealing with transit design in real systems, detailed descriptions of cities are too complex to allow an analytical formulation that leads to exact results, so heuristics have been used. Alternatively, optimal design of transit systems at a strategic level has been done based on simplified descriptions using regular patterns or small networks to face and solve ad-hoc transit design problems. In this paper we propose a parametric description of cities for the normative analysis of transit systems. This is achieved after a synthesis of different ways to describe a city's urban form that can be found in the literature, with an emphasis on the road network and the role of centers and subcenters. These diverse descriptions are assessed with the help of topological indicators and synthetic information regarding real cities. The parameters characterize the underlying network, the zones involved and the spatial pattern of transport demand, such that the design of public transport systems can be studied normatively for different city shapes. The model is applied to describe three very different real cities.