Defining the resolution of a network for transportation analyses: A new methodology and algorithm

Travel demand models are important tools used in the analysis of transportation plans, projects, and policies. Defining the level of detail (i.e. the number of roads) of the transport network in consistency with the travel demand model’s zone system is crucial for the accuracy of model results. All analyses found in the literature show that the spatial resolution of the transport network has great impact on the model results. If the zone system is fairly coarse, a network as detailed as the real road system will underestimate traffic congestion. Conversely, a network that is too coarse for a given zone system will over-represent congestion. However, there are no tools to determine how much detail is needed in a transport network to be compatible with a given zone system. This paper seeks to fill this knowledge gap by (1) providing a new methodology and algorithm to define an appropriate level of detail for a transport network under a given zone system, and (2) implementing this methodology for the Baltimore area. The results suggest that the transport network and the travel demand model’s zone system need to have a consistent level of resolution to provide reasonable model sensitivities. The evaluation of a new transportation project points out the importance of having an appropriate level of network detail for making reasonable planning decisions.