
TomTom, a provider of navigation information and digital maps, compiled historical speeds. The data was collected from customers who pay TomTom to help them avoid congested areas. Officials of TomTom say they analyzed data collected over the last two years from millions of GPS-enabled drivers.
A city's traffic was defined as congested if drivers could travel at 70 percent or less of the posted speed limit. In Seattle, an average of 43 percent of roads showed heavy delays. Rounding out the top five were Los Angeles, Chicago, San Francisco and New York. Minneapolis was the least congested with 17 percent of its roads congested.