By Jim Forsyth

SAN ANTONIO (Reuters) - American commuters, on average, spent more than a full work week stuck in traffic in 2011, a sign gridlock is making a comeback as the economy recovers from recession, a study released on Tuesday said.

Traffic jams on the way to or from work ate, on average, 38 hours of commuters' lives that year, up from 34 hours the year before, researchers from the Texas A&M University Transportation Institute found in an annual survey. That's nearly four hours longer than the average workweek.

Washington, D.C., where drivers spend 67 hours per year in traffic, was the most congested urban area for the second consecutive year, followed by Los Angeles, San Francisco, New York and Boston, the researchers found.

Traffic congestion reached its peak in 2005, when drivers spent an average of 43 hours a year in traffic.

"Prior to the economy slowing, congestion levels were much higher, and we really expect to see the conditions of congestion ... really go up as the economy improves," Bill Eisele, a TTI researcher and the co-author of the report, told Reuters.

The reduction in congestion had more to do with job losses than any coordinated effort by cities to move to alternate forms of transportation, Eisele said.

He said that peak congestion nationwide was on Friday from 6 p.m. to 7 p.m. while more than one-third of all delays occurred in the middle of the day.

The report found that 60 percent of delays occurred on streets and 40 percent on highways. Continued...