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

Use Code 25for25 at checkout for 25% off an annual plan!

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.

May 14, 2025 - Diana Ionescu

Front of Walmart store with sign.

Walmart Announces Nationwide EV Charging Network

The company plans to install electric car chargers at most of its stores by 2030.

May 7, 2025 - Inc.

Aerial view of Chicago with river in foreground.

Chicago Approves Green Affordable Housing Plan

The Mayor’s plan calls for creating a nonprofit housing corporation tasked with building affordable housing that meets Green Building standards.

May 8, 2025 - CBS News Chicago

Close-up on e-scooters parked in painted designated parking area on city street.

E-Scooter Parking: A Guide

How smart planning — and ample designated parking — can end conflicts over shared scooters.

7 hours ago - Streetsblog USA

Aerial view of Bozeman, Montana with mountains in background.

‘It’s Been 50 years’: Public Transit Law Passes in Montana

Legislation would fix transportation district issue, allow for greater reach on city bus routes.

May 14 - Daily Montanan

Illustration of nighttime city with white lines connecting nodes to illustrate technology and connectivity

Top 10 Tech-Ready Cities

An index ranks U.S. cities based on their preparedness for the ‘smart city future.’

May 14 - Smart Cities Dive