Traffic Equilibration: The Case of the Twin Cities Ramp Meter Shut Off

In Fall 2000, more than 430 ramp meters in the Twin Cities metropolitan area were shut down in order to evaluate the effectiveness of the metering system. This shutdown disturbed normal traffic patterns and thus traffic equilibrium. This paper examines how long it takes to establish a new equilibrium after a shock to the system, and thus establishes the basis for how long traffic studies should be carried out, as transportation analysts are generally concerned with comparing two equilibrium conditions. While traffic seems to be tending toward an equilibrium by the end of the 8 week shut-down, it has not yet converged to one. More research is needed to examine the question of whether and how equilibria form, and we need to examine longer time periods for analysis.