John Hourdos, Director, MN Traffic Observatory, Civil Engineering
The collapse of the Interstate 35W highway bridge over the Mississippi River in Minneapolis resulted in unexpected loss of life and had serious consequences on mobility and accessibility in the Twin Cities metropolitan area. In response to the network disruption caused by the bridge collapse, a number of traffic restoration projects were proposed and implemented by MnDOT in short order. Selection and prioritization of these projects, however, was based primarily on engineering judgment and experience; the only decision-support tool available to traffic engineers was the regional transportation planning model, which is static in nature and decennial. Although such a model is suitable for evaluating long-term (five years or longer) transportation investments, it is not appropriate or adequate for short-term (within days or weeks) operational planning in response to a disaster or other emergency. This was the driving force behind the creation of a comprehensive model of the Twin Cities freeway and major highway system that can support higher levels of traffic simulation resolution. Phase 1 of the development of the Twin Cities metro-wide freeway microscopic model covered the importation of the roadway geometry into a microscopic simulator, and generation of demand information for the entire model as well as for the calibration of as many individual segments as possible. In total, 1,199 directional kilometers of freeway mainline where included in the model. Including ramps and major highways, the number rises to 2,492 directional kilometers. The demand in the model is generated from 859 zones extracted from the regional planning model.