Estimating Lock Congestion

We consistently estimate the parameters of 600 and 1200 ft lock congestion func- tions by exploiting the geographical variation in demand patterns for individual locks along the Upper Mississippi River system of locks and dams. In addition to avoiding endogeneity bias, we control for lock-specific heterogeneity in estimating a fixed- effects regression model that relates lock congestion to lock usage and lock charac- teristics. Using a panel data set spanning the years 1993–2010, we find significant empirical evidence of the existence of a quadratic lock congestion function for 600 ft technology in the sense of BPR (1964). While 1200 ft technology on the other hand seemly operates under free-flow conditions, the presence of an auxiliary chamber significantly mitigates congestion, with the effect being more pronounced for higher levels of traffic. Unscheduled lock outages and non-commercial traffic attenuate lock congestion.