Estimation of Demand Response to Ramp Metering

Ramp meters in the Twin Cities were turned off for 8 weeks in the Fall of 2000. Previous research has assumed demand to be fixed when analyzing ITS technologies, however analysis of this ramp metering shut down experiment, using traffic count data from freeway loop detectors, suggests otherwise: for discretionary trips (non-work trips), the presence of ramp meters encourages people to defer short non-work trips, which then take place during unmetered times. Similarly, the absence of ramp meters discourages long peak-period non-work trips, which are deferred to off-peak times. The effects of ramp metering on non-discretionary demand (work trips) are also reflected by the spreading of the peaks. The method of using freeway traffic count data to estimate demand shifts developed in this paper can also be applied to other freeway demand analyses.