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44 the use not only of microsimulation but also of any advanced conditions are extremely dynamic, construction schedules and traffic modeling in the operations environment. staging schedules change daily, and events and incidents and First, it taught that advanced network traffic analysis is direly unforeseen contingencies, like the discovery of a bridge deck in needed to support high-impact operational decisions on a con- need of emergency replacement, will upend the best laid plans. gested urban freeway network. The cost of delay and of travel It can be expected that technology will continue to change. time unreliability to users, especially commercial users, is esti- Someday, there may even be real-time simulation. The chal- mated in the hundreds of millions of dollars. Given that mul- lenge to DOT business processes will be ongoing. For the pres- tiple concurrent construction-related closures are an ongoing ent, however, new, more dynamic processes will be needed if or annual occurrence, a scientifically sophisticated, systematic the full potential of the new traffic simulation technology is to approach must be implemented to plan for such disruptions. be realized. Second, the interdependent nature of a congested urban free- way network means that an incident or closure at one location References will usually have wide-ranging ramifications. Typically, there 1. FHWA, U.S. Department of Transportation. Work Zone Safety and are dozens of simultaneous projects in each other's influence Mobility Rule. http://ops.fhwa.dot.gov/wz/resources/final_rule.htm. areas whose closures need to be coordinated. Presently, net- Accessed July 19, 2011. work simulation is the only tool that can provide the traffic 2. Guidelines for Implementation of the Work Zone Safety and Mobility analysis needed to stage, coordinate, and mitigate multiple Policy. North Carolina Department of Transportation, 2007. 3. Hardy, M., and K. Wunderlich. Traffic Analysis Toolbox Volume IX: interacting projects. Work Zone Modeling and Simulation--A Guide for Analysts. Report Third, the business processes in an operations environment FHWA-HOP-09-001. FHWA, U.S. Department of Transportation, are radically different from those in a planning environment: 2009.