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TomTom’s Latest Traffic Study Reveals Most Polluting Roads in the United States

California roads have long been considered some of the most scenic, and congested, in the United States. A new study by location and navigation solutions leader TomTom gives them another distinction: the nation’s most polluting.

“As we approach Earth Day, a day in which we celebrate the environment, it’s incredible to see the impact of our daily commutes on the planet and ourselves”

The TomTom study shows the segments of roads on which vehicles produce the most carbon emissions, based on the length and time of average weekday traffic jams and the estimated number of vehicles in those jams. Of the top ten most polluting major, or interstate, roads in the country, seven are in California, including: I-5 South (#1); I 10 East (#2); I 405 South (#3); 60 East (#4); I 5 North (#6); 101 South (#8); and I 210 East (#9).

The results were calculated using data from Speed Profiles™, the historical speed database from TomTom’s licensing business unit Tele Atlas that helps personal and professional fleet drivers find the best routes. Speed Profiles aggregates, anonymously and on an opt in basis, the actual speeds that millions of GPS-enabled drivers have traveled over the last two years, providing the most accurate view of historical traffic on both primary and secondary roads. It is incorporated on TomTom GPS devices as IQ Routes™ to guide drivers away from congestion, not only on major highways but on all routes in the road network.

The data give the clearest picture yet of the impact of traffic jams on the environment, and on drivers’ wallets. Assumptions for carbon emissions and fuel consumption were based on relatively conservative calculations. TomTom’s study calculated that one vehicle stuck in congestion burns .1 gallons of additional fuel per hour, based on stopping and starting vs. idling, and that one gallon of fuel costs on average $3.00. Congestion on the roads in the study generally lasted for two hours. Calculations for emissions were for weekdays, or 300 days of the year. Traffic jams were defined as such if drivers could travel at only 70% or less of the posted speed limit, meaning on average an hour long trip included 20 minutes or more of significant delays.

Key findings are:

  • There are on average 120,000 cars stuck in traffic jams every day on the 170 mile section of California roads in the study.
  • Of the top ten most polluted stretches of roads in the nation, only three are outside California. They are: I 95 South in Virginia (#5); I 93 North in Massachusetts (#7); and I 95 North in Connecticut (#10).
  • Collectively, the ten most polluted road segments in the study produce 85,000 tons, or 170 million pounds, of carbon emissions every year. According to the carbon calculator from TerraPass, that’s the equivalent carbon footprint of one person taking 116,000 round trip flights from Boston to Los Angeles. To negate the effects, you would have to plant nearly 100,000 square miles of artificial forest on land the size of the state of Colorado.
  • The top ten most polluted major roads also have an impact on drivers’ wallets. Cars sitting in congestion don’t just idle but stop and start for extended periods, burning an additional .1 gallons of fuel per hour. At $3.00 per gallon, drivers sitting on these roads spend $30 million every year on wasted fuel.
  • Although they have fewer lanes, secondary or non interstate roads can be equally pollution-producing. The top ten most polluted local roads are: California 1 from Malibu to Redondo Beach; Virginia 7, from Washington D.C. towards Leesburg; Pennsylvania 611; Illinois 64; Georgia 120, from Marietta heading West; New York 25 between East River and Forest Hills; New York 25 A from La Guardia Airport heading East; New York 25 from Jericho to South Huntington; Virginia 7, through Leesburg; and Oregon 99 West, near Portland.

“As we approach Earth Day, a day in which we celebrate the environment, it’s incredible to see the impact of our daily commutes on the planet and ourselves,” said Product Manager Nhai Cao. “With products like IQ Routes on TomTom devices, and the pedestrian-friendly TomTom for iPhone, we’re proud to help people combat congestion, reduce the impact of their driving on the environment and save money.”

To see the full list of the top 20 most polluted major and secondary roads, the associated costs of that pollution in terms of tons of carbon emission produced and additional fuel wasted, or for more information, go to