California's I-405 has some of the worst congestion in the country. Flickr/Mike Spasoff Traffic in the United States is getting worse in 2013, and that's a sign of an improving economy, according to INRIX, which released its latest Traffic Scorecard Wednesday.

INRIX CEO Bryan Mistele told Business Insider the correlation between rising congestion and stronger employment numbers is easy to understand: More people working, and more businesses ordering and making deliveries, means more cars on the road.

While a good sign, more traffic is still a bad thing: The cost of wasted fuel and time cost Americans $121 billion in 2011.

The INRIX report also ranked the worst roads for traffic in the country in 2012.

Not surprisingly, it's dominated by highways in New York and Los Angeles:

Cross Bronx Expressway: Driver's on this NYC highway, the most congested in the country, waste more than six days in traffic every year. San Diego Freeway — I-405 (southbound): The worst time to travel LA's most congested freeway is Tuesday morning, when it takes 50 minutes to go eight miles. Van Wyck Expressway: Another rough stretch of NYC road, the average speed on Thursdays between 4 and 5 p.m. is just 10 mph. Santa Monica Freeway: Drivers should plan to take an hour to go the 15 miles from Lincoln Boulevard to Alameda. Riverside Freeway: Drivers waste about six days each year on this LA road. Long Island Expressway: Commuters using the LIE lose more than 30 minutes each day stuck in traffic. Brooklyn Queens Expressway: On a Tuesday evening, commuters take about an hour to go just 10 miles. San Diego Freeway — I-405 (northbound): This highway is so rough, it made the top ten list going in both directions. Dan Ryan/Kennedy Expressway: The only road on this list not in NYC or LA, Chicago's stretch of I-90 leads to O'Hare Airport. Santa Ana/Golden State Freeway: Driving 17 miles on weekday afternoons takes nearly 50 minutes.

INRIX provides traffic data to major automakers and commercial fleets, and in most cases recoups data from their vehicles on the road.

It cobbles that information together to provide live traffic reports, as well as long-term analysis.