, Former U of M Professor, Civil, Environmental and Geo-Engineering
Traffic simulation is only as good as its input data. Unfortunately, it is impossible to inexpensively measure entry ramp to exit ramp flows, which would be particularly useful for testing ramp metering control strategies. In the past, research supported by Mn/DOT and CTS has produced a viable method for estimating freeway origin-destination (O-D) patterns from loop detector data. This research further developed and applied those methods to estimate O-D demand for use in traffic simulation of freeway sections and corridors. The researchers required zone-to-zone traffic flows from a transportation planning model, and the flows entering and exiting on freeway ramps. Estimates of the traffic from each on-ramp to each downstream off-ramp in short time intervals (1 min. and 5 min.) were studied. This research included development and implementation of software that enables this method to be used conveniently with easy-to-collect data. Four methods were compared using both a simple network and the real Minnesota Trunk Highway 169 network. In order to expand these methods from freeways to general networks, the researchers concluded that route-choice has to be considered and the dynamic traffic assignment model would have to be incorporated into the estimation process for on-line applications.