Evaluating the Effects of I-35W Bridge Collapse on Road-Users in the Twin Cities Metropolitan Region.

Abstract

This study evaluates the effects of I-35W bridge collapse on road-users in the Minneapolis-St. Paul Metropolitan area. We adopted the 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 concluded that the failure of the I-35W bridge resulted in an economic loss of $71,000 to $220,000 a day, depending on how flexible road-users in the system can adjust their trip destinations in response to the bridge closing. We also estimated that the major traffic restoration projects Mn/DOT has implemented in quick response to the bridge collapse can save road-users $9,500 to $17,500 a day. This translates into a benefit-cost ratio of 2.0-9.0, suggesting these projects are highly beneficiary 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, showing its contributions in transportation planning under situations such as emergency relief and comprehensive design.