City-Scale Transport Modeling: An Approach for Nairobi, Kenya

Traffic congestion poses problems for cities around the world, especially in rapidly growing and motorizing cities like Nairobi, Kenya. We show here how we plan to use in the context of Nairobi a new theory that relates the mobility provided by a city’s street network to the number of vehicles on the network (including private cars and public transport) and to key aggregate descriptors of both the street infrastructure and the public transport services. Conventional micro-simulation models require vast quantities of data and produce unreliable detailed results. The new theory asserts that a micro-simulation of a simplified, abstract city resembling Nairobi in the key aggregate descriptors provides reproducible aggregate mobility predictions, and the effort in doing so is orders of magnitude smaller than with the conventional approach. Described in detail are the input data required to construct the idealized network including formal and informal public transport services and to calibrate the simulation model with current demand conditions. The outputs of the model and their practical use for scenario analysis are also discussed.