Acknowledgements & References

Acknowledgements

Rick Schuman, INRIX vice president of public sector, is the author of the INRIX National Traffic Scorecard and the driver behind the primary analysis of the metropolitan and bottleneck data.

INRIX historically works with data providers, technology partners, experts and our customers to address traffic issues in North America and Europe. Collaborating to create unique and important products is key to INRIX’s success. This Scorecard is no different. INRIX would like to thank several organizations and individuals who have assisted in one way or another in creating the approaches used in the annual Scorecard and also used in the mid-year Special Report. Tim Lomax and Shawn Turner of the Texas Transportation Institute, Rich Margiotta of Cambridge Systematics and Mark Hallenbeck of the University of Washington aided in development of the original Scorecard methodology. Kevin Loftus of INRIX’s partner Clear Channel Total Traffic Network provided local market knowledge and assistance.

Future Updates

Leveraging the nation’s most robust historical traffic data warehouse, INRIX is committed to publishing a report on an annual basis hat anlayzes the state of traffic congestion on our nation's roads. Based on input, feedback and the organic growth and expansion of our data sources, INRIX will continue to improve and expand the report in areas such as additional road coverage (the interstate network, arterials, additional metropolitan areas, etc.) and adding metrics, such as travel reliability and trending analysis.

There are many possible extensions and expansions to the information provided in this report. We welcome inquiries from public agencies and transportation data analysts to conduct more in-depth regional or national analyses based upon our traffic data archive and look forward to partnering to tap local knowledge and domain expertise to take full advantage of our data, and to incorporate and correlate with additional data sets (i.e., construction, incidents, weather, etc.).

INRIX also will continue to publish Scorecard Special Reports on key topics, similar to the mid-year 2009 report highlighting "the bottom of congestion" and a snapshot of findings from commercial freight's impact on traffic. INRIX also published, The Impact of Fuel Prices on Consumer Behavior and Traffic Congestion in Fall, 2008.

References & Scorecard Relationship with Other Studies

As one would expect for an issue as relevant to our daily lives and economic system as traffic congestion, there are many recently published studies on the issue. This Scorecard expands upon and complements these reports.

• 2009 Annual Urban Mobility Report (Texas Transportation Institute): http://mobility.tamu.edu/ums/
• Unclogging America’s Arteries: Effective Relief for Highway Bottlenecks 1999-2004 (American Highway Users Alliance): http://www.highways.org/pdfs/bottleneck2004.pdf
• Building Roads to Reduce Traffic Congestion in America’s Cities: How Much and at What Cost? (Reason Foundation): http://www.reason.org/ps346/state_by_state_congestion.pdf
• Freight Performance Measurement: Travel Time in Freight-Significant Corridors (Federal Highway Administration): http://ops.fhwa.dot.gov/freight/freight_analysis
• America’s Most Congested Cities (Forbes Life Magazine): http://www.forbes.com
• An Initial Assessment of Freight Bottlenecks on Highways (Federal Highway Administration): http://www.fhwa.dot.gov/policy/otps/bottlenecks/index.htm
• Where the Commuting Nightmares Are (bizjournals): http://www.bizjournals.com
• The Road... Less Traveled: An Analysis of Vehicle Miles Traveled Trends in the U.S.: http://www.brookings.edu/reports

Common elements

• The Scorecard adopts the common convention of peak period drive time hours of 6 – 10 AM and 3 – 7 PM, Monday through Friday.
• The Travel Time Index concept is now a standard metric to measure conditions relative to uncongested, free flow situations.

Unique features

• This report is based on data, technology and processes that have been designed to optimize very quick turnaround times between the end of the data collection period and the publishing of the Scorecard.
• Many of the reports utilize data that is many months or years old when published.
• The Scorecard is completely based upon real data – tens of billions of data points from real consumer and commercial vehicles traveling on real road segments. It is not limited by sensor coverage nor is it an interpolation of data.
• This is the first analysis to go to the detailed road segment level nationwide; it is also the first to look in depth by hour and day nationwide. Further, this report offers a unique opportunity to see trending by time, region or specific road segment.

Given the myriad of ways to calculate congestion and the wide range of raw data that is utilized, it is natural that different reports can have different results, rankings and indexes. When comparing differences between the Scorecard and other reports, it could be due to one or more of the following reasons:

• Many of the reports weight results by traffic volume and/or factor in the number of lanes on roadways; the Scorecard does not.
• Travel Time Index calculations are from a road user perspective based on complete random trips, not weighted by volumes, lane miles, or origin/destination weighting.
• Travel Time Index values in the Scorecard seem lower than some other studies. This is likely for two reasons:
  • By using a data driven reference speed instead of a flat speed for free flow, such as 60 mph, results in lower uncongested speeds in most cases, meaning less congestion is calculated for the same average speeds; and
  • INRIX coverage extends throughout entire metropolitan areas including highways and commuting corridors far away from city centers that may contribute less to congestion than roads in the urban core, lowering the index.
• Studies may have different metropolitan areas, or aggregate some regions such as Washington, D.C. and Baltimore. The Scorecard approach could easily adjust market boundaries to aggregate results differently, but is presently based on the standardized, Census CBSA definition.
• The Scorecard is focused on mainline lanes of limited access highways; other studies may include ramps, interchanges and arterials.