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Estimating Vehicle Hours of Travel

Posted by the U.S. DOT's Volpe National Transportation Systems Center

The Federal Highway Administration (FHWA) gathers data on vehicle miles traveled (VMT) to understand how the U.S. highway system is being used. But it’s also important to know how the system is performing.

FHWA turned to economists at the U.S. Department of Transportation's (USDOT) Volpe Center to develop a statistic that would provide insight on national roadway performance. Volpe estimated vehicle-hours traveled (VHT) based on speed and miles traveled data to measure the quality of service that America’s roadways provide.

Highway performance matters because our time matters. Time is a non-renewable resource, and it is a significant economic cost of traveling and shipping.

Developing America’s Travel Time Data

Volpe Center economists developed VHT by first obtaining vehicle counts for thousands of road segments from the FHWA Highway Performance Monitoring System (HPMS).

Then, the Volpe economists allocated daily car and truck travel on each segment by hour of the day and direction. And they match hourly speeds, measured by GPS, to each HPMS section.

Finally, they calculated VHT for cars and trucks during each hour of the day—hourly vehicle miles traveled divided by hourly average speed. Learn more about how Volpe developed VHT.

How FHWA Can Use VHT Data?

FHWA can now explore how VHT varies by peak and off-peak travel times, roadway type, state, and more. This new data may also help inform FHWA policy and planning decisions. Here are a few other ways FHWA may be able to use VHT data in the future:

  • Assess trends in highway performance and travel quality.
  • Compare performance by location and type of roadway.
  • Estimate economic costs of congestion.
  • Distinguish normal rush-hour congestion from delays due to incidents, construction, weather, and special events.
  • Map incident reports, construction, special events by date, time, and location to identify traffic hot spots.