Evaluating the effects of the I-35W bridge collapse on road-users in the twin cities metropolitan region

Abstract

This study evaluates the effects of the I-35W bridge collapse on road-users in the Minneapolis-St Paul, Minnesota Twin Cities metropolitan area. We adopted the Twin Cities Seven-County travel demand model developed in previous research, re-calibrated it against July 2007 loop detector traffic data, and used this model to carry out an evaluation of economic loss incurred by increased travel delay in alternative scenarios before and after the bridge collapse. We conclude that the failure of the I-35W bridge resulted in an economic loss of US$71,000 to US$220,000 a day, depending on how flexible road-users in the system adjusted their trip destinations in response to the bridge closing. We also estimate that the major traffic restoration projects Minnesota Department of Transportation has implemented in quick response to the bridge collapse can save road-users US$9500–17,500 a day. This translates into a benefit–cost ratio of 2.0–9.0, suggesting these projects are highly beneficial in an economic sense. In this analysis, the use of a simplified, scaled-down travel demand model enabled us to carry out the analysis quickly and accurately, which could see its contributions in transportation planning under situations such as emergency relief and comprehensive design.