Using GPS measurements from its traffic database to rank cities by congestion level hour-by-hour and for peak periods, TomTom measures congestion by the percentage increase in overall travel time compared to when traffic is moving freely.
The report finds that Moscow, which ranked first in 2012 and 2013, now ranks fourth, with 50 percent congestion levels, meaning that travel during peak times raises travel time by half. TomTom's 2012 and 2013 ratings showed that the city's burgeoning car ownership and the authorities frantic attempts to build sufficient new road infrastructure saw increases in travel times by up to 66 percent.
Istanbul, Mexico City, and Rio de Janeiro ranked ahead of Moscow, congestion levels there ranging from 51 to 58 percent.
St. Petersburg also made the top ten, coming in at number seven, with a congestion level of 44 percent. Other former Eastern Bloc cities to make the list include the Romanian capital of Bucharest (eighth place), and Poland's Warsaw (ninth). Warsaw apparently has even more to brag about than Moscow, having come in number three last year, and number one in 2011. Los Angeles rounded out the top ten, the only city the United States or Western Europe to make the ranking. Rome, London and Marseille made the top 20.