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Travel Demand Modeling Analyses Using ACS Data 149 Table 9.3. Available ACS flow (workers) data. Destination District Origin District 1 2 3 4 5 Total 1 36,545 14,945 2,705 1,750 2,070 58,015 2 15,433 18,385 3,680 1,584 2,405 41,487 3 23,805 25,423 21,954 5,110 5,549 81,841 4 16,020 15,455 5,700 13,650 4,275 55,100 5 10,160 8,105 1,790 1,955 5,245 27,255 Total 101,963 82,313 35,829 24,049 19,544 263,698 9.4 Specific Uses of Census Data for Travel Demand Modeling This section provides a list of specific examples of uses of census data by transportation plan- ners to do travel demand modeling. 9.4.1 Trip Generation Model input for base year is being performed at Indiana DOT. Census Bureau variables used in the statewide travel demand model include number of households, number of household units, population size, population age, number of children, average income, household income, total employment, occupation, number of autos per household, journey-to-work data, and land use information (residential density, accessibility, and urbanized area boundaries). Similar vari- ables are used by other DOTs and MPOs.108 Efforts involving trip generation rates include the following: The 1990 CTPP data were used by the Gainesville Urbanized Area to calibrate home-based work trip rates since its travel demand model was under assigning trips.109 The last available trip rates were from 1971. The Chicago Area Transportation Study, Vermont Agency of Transportation, and MTC (using PUMS data to create county-level calibration files) also have used census data to corroborate trip generation rates.110 9.4.2 Work Trip Mode Choice Modeling Examples of work trip mode choice modeling efforts include the following: Work done by the Denver Regional Council of Governments (where geographic market segments were identified and mode choice models were calibrated separately for each), 108 The DOTs and MPOs that have indicated the use of Census data in this context include: Des Moines MPO, Minnesota DOT, Vermont Agency of Transportation, Mass Highway, Broward County MPO, Hampton Roads Planning District Commission, Chittenden County MPO, Mid-Ohio Regional Planning Commission, Pioneer Valley Planning Commission, Tulare County Association of Governments, Pima Association of Governments, Yakima Valley Conference of Governments, and Caliper Corporation. 109 W. Blanton, 1996, "Small-Area Applications Using 1990 Census Transportation Planning Package: Gainesville, Florida." Proceedings of a Conference on Decennial Census Data for Transportation Planning: Case Studies and Strategies for 2000. 110 C. Purvis, "Uses of PUMS 2000 Data at the Metropolitan Transportation Commission," Transportation Research Board, National Research Council, Washington, D.C., 2004.

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150 A Guidebook for Using American Community Survey Data for Transportation Planning Central Transportation Planning Staff, Chicago Area Transportation Study, and Caliper Corporation;111 The use of PUMS data at MTC to create county-level calibration files for an auto ownership model; and The use of PUMS data and CTPP flow data at King County Transit to assess whether vanpool usage as inferred from the census matches with actual observations, in which case census data are used for further analysis. 9.4.3 Traffic Assignment Modeling An example of using census data to calibrate and adjust speeds and travel times in a traffic assignment model includes the analysis of New Jersey counties in the DVRPC region. 9.4.4 Demographic and Auto Ownership Models Examples of agencies/researchers using census data for demographic and auto ownership models include the following: Mid-Ohio Regional Planning Commission estimating models, using variables such as income and area type, for predicting the distribution of households by household size; Municipality of Anchorage, Central Transportation Planning Staff auto ownership model; Caliper Corporation auto ownership and employment models; Cambridge Systematics112 vehicle availability model for New Hampshire; and Auto ownership model for Honolulu, Hawaii.113 9.4.5 Microsimulation Examples of agencies/researchers using census data for microsimulation include the following: Census data are used at Caliper Corporation to validate aggregate employment shares. PUMS data are used for population synthesis for microsimulation models at Caliper Corpora- tion. Synthetic population estimates can be input to very disaggregate travel behavior models. Citilabs currently is building a tool for developing synthetic populations (e.g., demographic data for use in models) through sample enumeration using PUMS data. The developed population estimates will be controlled to full counts from the census. TRANSIMS114 creates synthetic household information using PUMS data. The "Population Synthesizer" routine in TRANSIMS takes in various types of census data at the census block and census block group level to generate synthetic households, individuals, and vehicles through a series of six steps. 111 At Caliper Corporation, CTPP data also are used for calibrating a time-of-day model and a destination choice gravity model related to work trips. 112 Cambridge Systematics, Inc., 1997, "Vehicle Availability Modeling." Prepared for FHWA. 113 J.M. Ryan and G. Han, "Vehicle-Ownership Model Using Family Structure and Accessibility Application to Hon- olulu, Hawaii." Transportation Research Record 1676, TRB, National Research Council, Washington, D.C., 1999. 114 Travel Model Improvement Program, U.S. DOT, 1998 "TRANSIMS: The Dallas Case Study." See http://tmip.fhwa.dot.gov/clearinghouse/browse, November 4, 2004.