Proving something local commuters already know, a study released Thursday shows that the Washington area has some of the nation's most congested highways.

D.C. commuters who drive 30 minutes to work each day spend an additional 80 hours a year in their cars because of congestion, according to a study done by TomTom, a company that makes GPS navigation devices.

D.C. ranks behind only Los Angeles and San Francisco when it comes to traffic-packed roads, the study shows.

Seattle, New York, Chicago and Miami all ranked behind D.C. in the company's quarterly study, which measures congestion worldwide by evaluating its customers' travel times during peak and off-peak hours.

Trips in the Washington area during rush hours took 26 percent longer than they would during nonrush hours, according to the study. Trips in Los Angeles took 34 percent longer during rush hours, and San Francisco peak trips were 29 percent longer.

"This report just reaffirms what every driver in our region experiences every day, and it's not just one of our routes, it's all over our region," said AAA Mid-Atlantic's Lon Anderson. "And it's simply because we have over the years been very fortunate and have had a strong economy. We've added business and homes and we've not added roads. And only occasionally have we added more mass transit."

Rush-hour travel times in Seattle and New York are 25 percent longer than off-peak travel, the study shows. They're 23 percent longer in Chicago and 22 percent longer in Miami.

The worst times to travel during the week are the Thursday morning and Tuesday evening rush hours, the study found. The least congested times were Friday morning and Monday evening.

Stewart Schwartz, who has criticized similar congestion studies in the past, sees a silver lining in TomTom's data.

"This is good news for the D.C. region," said Schwartz, the executive director of the Coalition for Smarter Growth."The boom in D.C. and near transit in the suburbs seems to be leading to real benefits, increasing transit, walking and bicycling and stabilizing peak-hour auto traffic."