Abstract
This paper is a commentary on findings that challenge the conventional flow-based representation of the supply-and-demand dynamic on a road network subject to congestion. Supply is distinguished from network performance, and demand is shifted from flow-based measures to ones that measure through-put. Among the implications of the work: the pattern and spatial and temporal profile of trips have an effect on overall demand. And a network's performance measures must take into account quite different average speeds and supply costs. (A)