Travels Impacts of Bridge Closures 2: Saint Croix River Bridges Final Report

Abstract

This report is prepared at the request Abby McKenzie and Ed Idzorek of MnDOT to assess the expected traveler impacts of replacing or not replacing the Saint Croix River Bridge in Stillwater, Minnesota. The model that has previously been used to evaluate different Lafayette Bridge replacement scenarios is applied, using the 20 county (“collar counties”) network from the Metropolitan Council and best estimates of 2010 land uses (population and employment). The model evaluates changes in travel cost due to network reconfigurations corresponding to different scenarios. These costs would need to be compared against construction and ongoing operations and maintenance costs, and do not account for factors such as travel time reliability, the value of a redundant network for planned or unplanned closures, or changes in land use. It can be safely assumed that were a wider, faster bridge constructed there would be more development, and thus more travel demand from the Wisconsin side of the Saint Croix River. If no replacement bridge were built, we can assume that less growth (if any) would occur, and cross-river traffic would diminish. This model does not account for changes in land use, as we do not believe this has been accurately forecast for scenarios both with and without the bridge, but does account for changes in demand given the current land use under different network configurations. This is denoted as “Variable Trip Tables” in the report. Compared to the baseline (a replacement 2 lane bridge in the same location) according to the model, Construction Alternative 1, a new 4 lane bridge, produces an economic gain of $1.8 million per year. Compared to that same baseline, Construction Alternative 3, no replacement bridge at all, results in an economic loss on the order of $34.1 million per year according to the model.