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Travel Modeling and the National Household Travel Survey

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Travel Modeling and the National Household Travel Survey

Brad Gudzinas
FHWA Office of Highway Policy Information

Highway Information Seminar
November 17, 2011

 

 

 

 

 

Travel Modeling and the National Household Travel Survey

Who’s traveling? To where?

Who's traveling? To where? - map of the u.s.

 

Travel modeling

  • Predicting travel behavior
    • Socioeconomic changes
  • Understanding cause-and-effect relationships e.g. "What happens when gas prices change?"
  • Quantitative analysis for infrastructure investment and operational effectiveness
  • Emergency planning

 

Travel modeling

  • Freight has FAF (Freight Analysis Framework), but nationwide passenger travel model lacking
  • States are collecting long-distance travel data and also develop statewide travel models, but they are not necessarily compatible; no "unified"
  • long-distance modeling

 

The role of NHTS

  • NHTS helps us understand these travel patterns
  • It is the only nationwide survey of its kind and provides valuable data for many different users

 

Building a national transportation model

National Transportation Model - As shown in the grid(counterclockwise) - Data, Locations, Modes, and Routes

 

Building a national transportation model

Data - Part of the Transportation Model
  • Primarily 1995 ATS and 2001 NHTS for estimation
  • Airline, other modal data available
  • Commercial data vendors
  • Start with good data
  • Limitations of existing data

 

Building a national transportation model

Data - Part of the Transportation Model
  • Geographic distribution of trips
  • Can start with a base O-D matrix and factor, or
  • Size of zones (not too big, not too small) requires trade-offs
  • More zones equals larger O-D matrix, more challenging to estimate accurately

 

Building a national transportation model

Data - Part of the Transportation Model
  • Primarily auto trips
  • Auto vs. air on trips >500 miles
  • Bus / train in some areas
  • Trip purpose matters (leisure and business)
  • Usually modeled as discrete choice but other forms may be better

 

Building a national transportation model

Data - Part of the Transportation Model
  • Routing trips on national transportation network
  • Door-to-door access modes (e.g. how to get to airport)
  • Both passenger and freight travel use the same networks (multi-class assignment)

 

Considerations

  • Start with consistent and reliable data
  • Time period: Most people rarely make long-distance trips, but a few make many
  • Areal structure: necessarily course zones (˜65,000 census tracts, ˜3,100 counties)
  • Model resolution: individual trip-making or aggregate trips

 

Considerations

  • Additional relevant components (party size, advance scheduling)
  • Integration with statewide models (external trips)
  • Passenger and freight (FAF) routing
  • Trade-offs
    • Complexity vs. simplicity
    • Accuracy vs. validity (statistically valid cell values)
    • Matrix size vs. file size

 

Current FHWA initiatives

  • Origin-destination matrix estimation
  • Long-distance mode choice model
  • Long-distance travel model exploratory research (EARP)

 

Questions?

Brad Gudzinas
FHWA Office of Highway Policy Information
brad.gudzinas@dot.gov