We are extremely grateful to B. Stein, D. Walker, K. Lawton, and others at Portland Metro for providing the data for the Portland/Oregon area, without which this study would not have been possible at all. Much of the work was done while the authors were at Los Alamos National Laboratory (LANL) and at Santa Fe Institute (SFI). We thank the Transims project at LANL for providing the technical infrastructure necessary for running these studies.