Travel Demand Forecasting: Parameters and Techniques (2012) / Chapter Skim
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Pages 14-26
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From page 14... ...
Once the zone system is developed and mapped and a census equivalency table is constructed, zonal socioeconomic data can be assembled for the transportation planning process. Estimates of socioeconomic data by TAZ are developed for a base year, usually a recent past year for which necessary model input data are available and are used in model validation.
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The PUMS files contain records for a subsample of ACS housing units and group quarters persons, with information on the characteristics of these housing units and group quarters persons plus the persons in the selected housing units. The Census Bureau produces 1-year, 3-year, and 5-year ACS PUMS files.
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with Census Transportation Planning Products (discussed below)
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Previously called the Census Transportation Planning Package, the Census Transportation Planning Products (CTPP) Program (AASHTO, 2011)
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All models include a highway network; models that include transit elements and mode choice must also include a transit network. Sometimes, a model includes a bicycling or a walk network.
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Questions can be directed to the DOT; and such a working relationship between DOT and MPO helps the modeling process because both parties understand the network data source. Highway Network Attributes Highway links are assigned attributes representing level of service afforded by the segment and associated intersections.
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Higher speed and capacity than arterials, but lower than freeways Major Arterials Links representing roadways with traffic signals serving major traffic movements (high speed, high volume) for travel between major points.
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Transit Line Files Local bus line files are established "over" the highway network. Sometimes nodes and links, which are coded below the grain of the TAZ system, must be added to the highway network so that the proximity of transit service to zonal 2Facilities experiencing greater-than-typical truck traffic (say, greater than 5 percent for urban facilities; greater than 10 percent for nonurban facilities)
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Transit network characteristics and definitions. Transit Network Characteristic Description Drive access link A link that connects TAZs to a transit network via auto access to a park-and-ride or kissand-ride location.
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Again, the best source for determining which zones should have auto access is an on-board survey of transit riders. Travel Times and Fares The time spent on transit trips -- including time spent riding on transit vehicles, walking or driving to and from transit stops, transferring between transit lines, and waiting for vehicles -- must be computed.
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For example, the HPMS has network data that may be used to check model networks. Quality assurance applies to transit networks, as well as highway networks.
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Trip Distribution Trip length frequency distributions (time and distance) by market segments Worker flows by district District-to-district flows/desire lines Intrazonal trips External station volumes by vehicle class Area biases (psychological barrier -- e.g., river)
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From page 26... ...
by direction by time of day Assigned versus observed vehicles (or vehicle miles traveled) by functional class Assigned versus observed vehicles by vehicle class (e.g., passenger cars, single-unit trucks, combination trucks)
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