Using microsimulation to evaluate traffic incident responses for traffic operations center decision making

One of the major challenges for Traffic Operations Center (TOC) operators is to determine the nature of their response to traffic incidents. This applies to both operators' training and real traffic management. While incidents vary by location and degree of disruption, operators' responses vary by how quickly they are implemented and what degree of actions they take. Operators can react instantaneously and divert traffic from an entire highway, or simply wait and apply a mild variable message. Travelers' delay under incident conditions depends not only on incident severity, but also on the effectiveness of response to an incident. This is an analysis of a wide range of incidents and responses for the set of critical locations on a test Salt Lake Valley freeway network. It uses VISSIM microsimulation to determine optimal responses under various incident conditions. Incident severity is represented through Incident Location, Incident Duration and Lane Closure. Incident response is defined through the Response Time, and Variable Message Sign (VMS) Levels and VMS Display Time. As expected, the resulting degree of incident disruption is mitigated by the speed of response and the proportion of drivers who divert. However, for certain minor incidents, a VMS induced traffic diversion might increase travelers' delay instead of reducing it.