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Travel Time Index

Dataset Excel: 

The Travel Time Index is the ratio of travel time in the peak period to the travel time at free-flow conditions. A value of 1.35 indicates a 20 minute free-flow trip takes 27 minutes in the peak. Free-flow speeds (60 mph on freeways and 35 mph on principal arterials) are used as comparison threshold.

Methodology and data sources have been changed in 2015; these figures are not comparable to those in past editions of NTS. Population group is based on 2014 population.


KEY: NA = not applicable; R = revised; U = data are not available.

Very large urban areas – 3 million and over population.

Large urban areas – 1 million to less than 3 million population.

Medium urban areas – 500,000 to less than 1 million population.

Small urban areas – less than 500,000 population.

a Rank is based on the calculated point change with the highest number corresponding to a rank of 1.

b  Averages weighted by Vehicle Miles Traveled.

c  MSA are the 52 largest metropolitan areas in the United States


1982-2014: Texas Transportation Institute, Congestion Data for Your City, Excel spreadsheet of the base statistics for the 101 urban areas and population group summary statistics (College Station, TX: 2015), available at as of Nov. 19, 2015.

2015-18: U.S. Department of Transportation, Federal Highway Administration, Urban Congestion Reports, Personal Comunication, Apr. 12, 2019.