Delivering resources to save time, lives, and money

2011 Congested Corridors Report


This inaugural report uses 2010 INRIX traffic data to analyze 328 specific (directional) freeway corridors in the U.S. for congestion conditions and reliability. Detailed hour-by-hour data revealed when and how congestion occurs, and allowed the authors to suggest how much extra “buffer” time is necessary. Specific performance measures—presented on total (annual) and peak period (6 to 10am and 3 to 7pm) bases—include: extra travel time, increased fuel consumption, congestion costs, and reliability.

Two reliability measures were developed:

  • Planning Time Index – the total travel time that you should plan for a trip; it differs from the Buffer Index by including typical delay as well as unexpected delay
  • Buffer Index – amount of extra “buffer” time needed to be on time for 95 percent of trips

The congested corridors are presented in tabular groupings that illustrate different peaking characteristics:

  • Table 1 – Reliably Unreliable (top 40 corridors ranked by buffer index, with all 328 corridors in an appendix)
  • Table 2 – Congestion Leaders (top 40 corridors ranked by delay per mile, with all 328 corridors in an appendix)
  • Table 3 – 3-cup Mornings (top 40 corridors for morning peak period delay per mile)
  • Table 4 – Dog Day Afternoon (top 40 corridors for afternoon peak period delay per mile)
  • Table 5 – Lunch Bunch (top 40 corridors for mid-day delay per mile)
  • Table 6 – Weekend Warriors (top 40 corridors for weekend delay per mile)
  • Table 7 – Where the Big Trucks Are (top 40 corridors for truck delay per mile)
  • Table 8 – One-Hit Wonders (corridors in cities with only one or 2 corridors from the 328 corridors)

Source Organization Location

College Station

Operations Area of Practice

    Performance Management
    System Performance Definition, Monitoring and Reporting
    Cost / Benefit Analysis

Content Type


Role in Organization

Transportation Planner
Senior Engineer
Principal Engineer
Manager / First Line Supervisor
Director / Program Manager
Senior Manager
Transit Professional

Publishing Organization


Maturity Level of Program

Monitoring (L4)
Deployment (L3)
Assessment (L1)
Development (L2)



Document Downloads

Project Website

Prime Contractor
Texas A&M Transportation Institute
Issue Date