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An Innovative Approach to Truck Modeling

A Federal Highway Administration freight analysis forecasts that freight tonnage and truck vehicle miles of travel (VMT) will double in the next twenty years. Interest in modeling truck traffic will, therefore, increase in response to increasing truck traffic in many areas. The traditional approach to creating a truck model has been to conduct a survey on truck movements to use to develop a model of truck trip rates, distribution patterns, and routes. This approach is generally not feasible, however, due to the difficulty and high cost inherent in conducting a statistically valid truck survey. An innovative, faster, less costly approach to developing a truck model has been developed using a technique called “adaptable assignment.” Adaptable assignment is a practical method of synthesizing a trip table from count data. Detailed classification count data was available at over 600 locations throughout the Baltimore Metropolitan council (BMC) modeled network. An initial model was created using parameters from another urban area. This initial trip table was modified by the adaptable assignment process, to produce a new table whose assignment much more closely matched the count data. The resulting trip table was systematically compared to the initial table to understand the differences. Numerous adjustments were then made to the initial model to reflect those differences. An improved method of estimating external travel was also developed. The final model consists of standard generation and distribution steps, a table of calibration adjustments, and an assignment process that specifically recognizes trucks. The calibration adjustments are applied to all future trip tables. This process was applied twice, to develop separate models for Medium Trucks (F5 vehicles in the FHWA classification scheme) and Heavy Trucks (F6-F13). The new models were incorporated into the framework of the Baltimore Region Travel Demand Model and the TP+/VIPER software. The Baltimore Region Travel Demand Model is the traditional four step model maintained by BMC staff for air quality conformity analysis, corridor studies, and long range planning. The new process for modeling accounted for areas of heavy trucking activity, land use, truck prohibitions, and truck passenger car equivalencies (PCEs). In areas of heavy trucking activity, e.g., port facilities, land fills, etc., a total of 127 truck special generator zones were identified. The model results showed significant improvement over the previous model and compared well to traffic count data. This presentation describes the process of developing a truck model using “adaptable assignment,” presents model results, and discusses the benefits of this approach over traditional methods.

Language

  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; Maps; Photos; References; Tables;
  • Pagination: 10p
  • Monograph Title: Proceedings of the Ninth TRB Conference on the Application of Transportation Planning Methods, April 6-10, 2003, Baton Rouge, Louisiana

Subject/Index Terms

Filing Info

  • Accession Number: 01024654
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: May 25 2006 7:57AM