Supply Curves for Urban Road Networks

Supply curves are essential for demand prediction in aggregate networks, and need to relate cost of use to flow demanded rather than to flow performed. The paper defines the parameters of relevance and the relationships required. A microsimulation model is used to generate such relationships for hypothetical networks. Network performance curves can exhibit backward-bending relationships between speed and flow performed, but these curves are inappropriatefor demand prediction. Relationships between speed and flow demanded are monotonic, but not necessarily linear. They can exhibit spatial and temporal dependencies, both of which requires them to be re-estimated if demand patterns change.