Peak Travel in America

Understanding peak period travel is vital for transportation finance initiatives, congestion mitigation, and air quality policies among other important policy and planning programs. Historically, the peak period was considered the domain of work travel. Commuting is still predominantly a weekday activity, tied to the morning and evening hours, and has traditionally defined peak travel demand. Over the last four decades the number of work trips grew as the population of workers grew. But by the early 80’s the National Household Travel Survey (NHTS) showed that the number of non-work trips were growing faster than work trips. By the early 90’s the concept of trip chaining during a work tour was commonly used to allow more complex commutes to be recognized as work travel by including stops for incidental purposes during the commute. Even beyond the growth in trip chaining, non-work travel continues to grow faster than work travel, and it is growing during the peak periods. As the authors look forward to initiatives that aspire to smooth travel demand across time periods, one question that is difficult to answer is ‘How much of peak period travel is really mandatory?’ This research utilizes the NHTS data chained trip files (2001 are the most recent available, but this analysis can be updated in late fall with the 2008 NHTS) to categorize peak weekday vehicle travel into Mandatory travel; including work and school trips with typically more rigid schedules and fixed destinations; and Flexible travel; such as getting a meal and going to the gym that may be less rigid in time or destination choice. The concept of a work tour is used to include incidental non-work stops into the commute and therefore the ‘Mandatory’ category. The trips classified as ‘Flexible’ are trips wholly separate from the commute tour. This research concludes that using very stringent definitions of Mandatory travel (for instance, not including trips for medical purposes) nearly 75 percent of am peak vehicle trips are for ‘Mandatory’ purposes. In contrast, only 34 percent of PM peak vehicle trips are ‘Mandatory’. Importantly, we find that the mean income of peak travelers is slightly lower than the average for all travelers. Workers with the least flexible schedules, such as people in sales and service occupations, are more likely to be commuting during the peak. Part-time workers and workers in households with children are more likely to make ‘Flexible’ trips during the peak, and many (38 percent) of the workers making Flexible trips during peak go to work at another time, indicating schedule constraints on their Flexible travel.


  • English

Media Info

  • Media Type: DVD
  • Features: Figures; References; Tables;
  • Pagination: 17p
  • Monograph Title: TRB 89th Annual Meeting Compendium of Papers DVD

Subject/Index Terms

Filing Info

  • Accession Number: 01155043
  • Record Type: Publication
  • Report/Paper Numbers: 10-1762
  • Files: TRIS, TRB
  • Created Date: Jan 25 2010 10:48AM