NEW YORK (Reuters) - The Los Angeles metropolitan area led the nation in traffic jams in 2005, with rush-hour drivers spending an extra 72 hours a year on average stuck in traffic, according to a study released on Tuesday. The metropolitan areas of San Francisco-0akland, Washington, D.C.-Virginia-Maryland, and Atlanta were tied for the second most gridlocked areas, according to the study by the Texas Transportation Institute. Drivers in those three areas spent an extra 60 hours on average during peak periods, defined as 6 a.m. to 9 a.m. and 4 p.m. to 7 p.m., the study found. But drivers in other regions around the country were not much luckier. The report (http://mobility.tamu.edu) found traffic gridlock worsened in all 437 large, medium and small urban centers in 2005. "What causes congestion? In a word, 'you.' Most of the Mojave Desert is not congested," wrote report authors David Schrank, associate research scientist, and Tim Lomax, research engineer. The Texas Transportation Institute is an arm of the Texas A&M University System in College Station, Texas. In the last 20 years, travel has increased by 105 percent in metropolitan areas but road capacity -- measured by freeways and major thoroughfares -- has only risen 45 percent. Travel by public transportation in 85 urban areas climbed 30 percent in the past two decades. The study found that drivers in the Dallas-Fort Worth-Arlington, Texas, area had average delays of 58 hours. San Diego drivers faced an average delay of 57 hours, and Houston drivers had an average delay of 56 hours. Detroit was in a three-way tie with San Jose, California, and Orlando, with average delays of 54 hours, according to the report. Traffic forced U.S. urban dwellers to travel 4.2 billion hours more and buy an extra 2.9 billion gallons of fuel in 2005, for a total cost of $78 billion, the study said. That worked out to 220 million more hours and 140 million more gallons of fuel than in 2004, with the total cost rising $5 billion. Solving the problem not only includes focusing on "critical" corridors and easing choke points but making work schedules more flexible and building more areas where people can walk to work, the study said.