If you drive in San Diego, you'll need to set aside an hour if you want to arrive on time, according to the Texas A&M Transportation Institute.
The study analyzed congestion patterns in 498 of the nation's urban areas in an attempt to give drivers and shippers reliable driving times.
Drivers in San Diego need to add 58 minutes to a routine 20 minute trip if they want to arrive on time, the study found.
The findings coincide with local data released last month, which found that San Diego traffic is worsening.
The institute also reported that in 2011, congestion caused Americans to travel 5-and-a-half billion extra hours. Drivers also had to buy an extra 3-billion gallons of fuel, for a cost of $121 billion.
The year's "top 10 are repeat performers" were Washington, D.C., followed by Los Angeles, San Francisco-Oakland, New York-Newark and Boston.