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