Statewide travel models differ somewhat from urban and regional models in that they need to explicitly consider long-distance travel that may be made on a relatively infrequent basis in comparison to typical urban and regional travel (typically 0.5-3.0% of total trips), but they represent a higher share of VMT. In addition, while urban and regional models typically consider trips or tours that typically start and end the day at a person's home, statewide travel models must consider travel that do not start or end the day at a person's home.
# Definition of Long-distance Travel
Various definitions have been used to define long distance travel. A frequently used threshold is 50 miles.
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The modeling of long-distance trips in statewide models differs from that of urban and regional models that focus on differentiating home-based from non home-based trips. Long-distance trips are more likely to be divided into categories by frequency of travel or by purpose such as recreational/tourist versus business-oriented trips. Such considerations are more likely to be indicative of long-distance variations by trip length, mode choice, and other aspects of travel...
# Data Sources
In the context of statewide forecasting, long-distance trip-making... constitute(s an) important market segment(s), much more so than in urban models. Information describing these markets, and how these markets vary from state to state, is somewhat sparse, and many states do not have the resources to initiate original data collection to develop a set of model parameters... The 1995 American Travel Survey (ATS) datasets are dated; however, these data are the only long-distance data that provide statistically sound estimates of long-distance travel in and between the states. Although the 2001 National Household Travel Survey (NHTS) had a long-distance component, this survey did not have sufficient samples to calculate estimates of long-distance travel for most states (New York and Wisconsin were exceptions to this, because of the large add-on in the former and stratified sampling of the latter, although neither add-on was included in the official 2001 NHTS long-distance file)." onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_735.pdf
NCHRP Report 735 Transferable Parameters for long distance and rural trip-making (2012) is a valuable source of information on long distance travel. The NCHRP report explains how statewide models have fundamental differences from urban models due to long distance trip making and rural trips. The report contains chapters on:
- long distance data sources;
- transferability and typologies;
- trip generation parameters and benchmark statistics;
- auto occupancy and mode choice parameters; and
- conclusions /comparisons.
The report also contains the following appendices:
- Recent examples of long-distance travel demand studies (ORNL, UMD);
- Travel behavior data from other countries;
- Modal-based travel data;
- Other demographic and origin-destination data;
- Urban versus rural truck trips; and
- Review of statewide models.