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32 I N N O VAT I O N S I N T R AV E L D E M A N D M O D E L I N G , V O L U M E 2 Model 8 covers stops and trip mode choice. This possibility estimated by the models, with use of a ran- model determines whether any stops are made on either dom number series to determine which possibility is cho- the outbound (from home), or inbound leg of the tour sen for that record. Both the population synthesizer and and the location of those stops. Furthermore, given the the automobile ownership models, however, perform the overall tour mode previously determined, the exact mode microsimulation through a deterministic discretizing the traveler uses for each segment or trip on the tour is procedure that avoids Monte Carlo variability. The new determined on the basis of a set of rules. Each of these model is applied with an implementation of three global trips is connected, and all stops are based upon the pre- feedback loops for consistency between highway travel vious choices. Therefore, if the main tour mode is tran- times that are both used as inputs to, and as forecast out- sit, then a person will not be able to choose to drive alone puts of, the model. for a lunch trip made at work. Furthermore, if the pri- The new model is being used by MORPC for confor- mary mode of a tour is by automobile, then a person mity analysis, transit alternative analysis, and highway- would be allowed to drop off a child at school and then related management information systems projects in the drive to work. The final trips are then aggregated by Columbus region. It is being used to generate forecasts zones and assigned as conventional trip tables to the for the North Corridor Transit Project (NCTP), currently highway and transit networks. in the draft environmental impact statement stage, with a The core choice models (Models 1 through 8 as potential New Starts submittal within the next few years. described above) are applied in a disaggregate manner. The NCTP is analyzing various travel modes along a 13- Instead of using aggregate fractional probabilities to esti- mi corridor that includes three major employment mate the number of trips, the new model is applied by centers--the Central Business District, Ohio State Uni- microsimulation of each individual household, person, versity, and the CrosswoodsPolaris area--interspersed or tour, mostly using Monte Carlo realization of each with large residential areas.