A study by an advocacy group found the nation's worst traffic bottleneck in terms of hours of delay is a stretch of Chicago's Kennedy Expressway.

The study released Monday by the American Highway Users Alliance assessed bottlenecks, finding that the top 30 cause at least one million hours of delay each per year and three million on average.

The study found the top 50 bottlenecks are concentrated in the nation's largest cities, with the worst being a 12-mile stretch of the Kennedy Expressway near Chicago's Loop business district. The study asserts that congestion cost motorists 16.9 million hours last year and about 6.3 million gallons in wasted fuel.

Eleven of the 30 most severe chokepoints are in the Los Angeles region, with the New York metropolitan area home to five. The I-35 corridor running through downtown Austin, Texas, is 10th.