Same Source Data, 'Contradictory Conclusions' on Congestion

A curious discrepancy between two major congestion reports using the same data: There is a profound and unexplained discrepancy between the travel trends in the latest Urban Mobility Scorecard report and the data provided by Inrix.

2 minute read

September 3, 2015, 8:00 AM PDT

By Todd Litman


The Texas Transportation Institute's Urban Mobility Scorecard claims that congestion increased by about 4.7 percent between 2010 and 2014. However, INRIX, which provides the source data used for the Scorecard, actually reported that U.S. traffic congestion declined 29 percent from 2010 to 2014. The new TTI report neither acknowledges nor explains the discrepancy between its tabulation of these data and the one prepared by INRIX.

A new post by Joe Cortright of the City Observatory, "Contradictory Conclusions and Disappearing Data," discusses these discrepancies. Of course, different analyses can produce very different conclusions using the same data, reflecting different analysis assumptions and techniques. Basic academic practices requires researchers to explain their methods in detail, respond to questions and criticisms, and apply peer review, but TTI has so far refused to respond to such requests.

In addition, after the TTI report was released, the link to the monthly INRIX data for 2010 through 2014 was removed from their website. The original INRIX Tableau data has been hosted on a separate public server. 

So here's where we currently stand: A separate tabulation of the same data that TTI used for its report concluded that congestion actually declined 29 percent between 2010 and 2014, rather than increasing 4.7 percent as TTI claimed. TTI has never acknowledged this different tabulation of the Inrix data, nor explained why its methodology produces such a different result. The link to the contradictory data has been removed from the Inrix website (although, the data are still available on a public server).

These facts raise important questions about the quality of TTI research and the reliability of the Urban Mobility Scorecard results.

Wednesday, September 2, 2015 in City Commentary

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Get top-rated, practical training

Close-up of "Apartment for rent" sign in red text on black background in front of blurred building

Trump Administration Could Effectively End Housing Voucher Program

Federal officials are eyeing major cuts to the Section 8 program that helps millions of low-income households pay rent.

April 21, 2025 - Housing Wire

Logo for Planetizen Federal Action Tracker with black and white image of U.S. Capitol with water ripple overlay.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

April 23, 2025 - Diana Ionescu

Ken Jennings stands in front of Snohomish County Community Transit bus.

Ken Jennings Launches Transit Web Series

The Jeopardy champ wants you to ride public transit.

April 20, 2025 - Streetsblog USA

Yellow electric school bus with preteen students exiting.

California Invests Additional $5M in Electric School Buses

The state wants to electrify all of its school bus fleets by 2035.

April 25 - Associated Press

City Hall building in Austin, Texas.

Austin Launches $2M Homelessness Prevention Fund

A new grant program from the city’s Homeless Strategy Office will fund rental assistance and supportive services.

April 25 - Spectrum Local News

Brick school building with mid-sized tree on front lawn.

Alabama School Forestry Initiative Brings Trees to Schoolyards

Trees can improve physical and mental health for students and commnity members.

April 25 - Governing