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54 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 1 10,694 centroid and external connectors, and 10,765 across different household members, transit accessibility, facilities classified as other. The network uses unidirec- and automobile availability to determine the number of tional or dualized coding. The geographic information journeys for each individual. system street network is based in TIGER or LION using The next step in the model is mode and destination TransCAD software. The modes included in the highway choice, which also consists of three submodels: destina- network are single-occupant vehicles, two-person high- tion and mode choice, stop frequency, and stop location. occupancy vehicles (HOV-2), three-person high- The model distinguishes between motorized and nonmo- occupancy vehicles (HOV-3), taxi, truck, and other torized travel based on household characteristics and the commercial vehicles. The network is classified by 21 density related to the journey and the region. The con- physical link types for capacities, initial speeds, and cept of intermediate stops is also presented in the sub- volume-delay functions. model. The number of intermediate stops on both legs of The transit network includes extremely detailed the journey is estimated. transit coding based on information from the Metropol- The NYBPM is being used in a number of applica- itan Transit Authority and New Jersey Transit. The net- tions. Examples of applications included air quality con- work was developed in TransCAD 4.0. Each route formity analyses, regional transportation plans, variation is coded as a distinct route. There are 100 New congestion management system plans, and testing sce- York City subway routes, 900 commuter rail routes, narios for emission reduction strategies. The NYBPM 2,300 bus routes, 73,000 transit stops, and 50 ferry has also been used for data manipulation and analyses routes. The system also includes the sidewalk network in requested by other agencies in the area. Manhattan, walk access and egress links, and park-and- The model has been used with major investment ride facilities. studies on the Tappan Zee Bridge, the Gowanus Express- The NYBPM is a microsimulation choice model. It way, and the Bruckner Sheriden Expressway. It has also uses population synthesis and intrahousehold travel been applied in the Long Island East Side study, the interactions. Journey-based travel units are modeled. Canal Area Transportation study, the Southern Brooklyn Nonmotorized modes are included in the premode Transportation study, the Bronx Arterial Needs study, choice portion of the model. Mode destination choice and the Regional Freight Plan study. It has been used to uses a nested logit model. There is a stop frequency and assist the Hackensack Meadowland Development Cor- location submodel, which uses full multimodal analysis poration and the Lower Manhattan Development Cor- and assignment. poration with studies. Traditional travel demand models focus on the trip The NYBPM is important for a number of reasons. origin and the trip destination, not intermediate stops. It was one of the first activity-based models to be used in The NYBPM uses the journey as the unit of travel. A air quality conformity analysis. It covers one of the most journey reflects the real travel characteristics. A complex regions in the world. The NYMTC's staff expe- traditional four-step model is also available. The general rience with NYBPM is of benefit to other metropolitan modeling structure includes journey generation, mode planning organizations. A rigorous review process and destination choice, time of day, and assignment. involving all the stakeholders was conducted on the Microsimulation is used in the first three steps. model. Topics covered with experience to date include Journey generation consists of three submodels: model-related issues, user training, staffing issues, insti- synthetic population, automobile ownership, and jour- tutional issues, and future improvements. ney frequency. The synthetic population submodel fore- One of the model-related issues focuses on the casts the number and the distribution of households by timeliness and the completeness of input data. The devel- income, size, number of workers, number of nonwork- opment of the model was initiated in the mid-to-late ing adults, and number of children in each zone. The 1990s. The model was completed and implemented in source of the data is the 5% census public use microdata 2002. The September 11, 2001, attack on the World sample (PUMS) files. The automobile ownership sub- Trade Center had a major impact on the model because model determines the number of automobiles available of the resulting changes in travel in the region. Addi- for each household. The model considers the influence of tional data collection activities were conducted to better household income, the household composition, vehicle understand these impacts. maintenance costs, parking availability, highway and Other modeling issues relate to the need for a dif- transit accessibility, and density and residential area type. ferent level of details and modeling documentation. The The journey frequency submodel determines the daily consultant or model developers' view of documentation number of journeys for each individual in each house- is often different from the needs of the end user. The gap hold for each purpose. Individuals are categorized as between the availability of proper documentation and working adults, nonworking adults, or children. The the completion of the model can also be an issue. The submodel evaluates the intrahousehold interrelationship modeler is frequently not the best person to complete the