HOUSTON – Just as Americans started worrying a little less about jobs and money, they got something new to fret about: More traffic.

An annual study done by the Texas Transportation Institute at Texas A&M University found that traffic was better than it had been in a decade during the height of the recession. But roads snarled once again as people returned to work and shopping.

Using real-time data to calculate commuter mileage, speed and distance traveled over time, the institute estimated traffic tie-ups cost about $115 billion in 2009. The study released today cites factors such as wasted fuel, lost work hours and delays in shipping goods.

Commuters in Chicago and Washington suffered the most, losing 70 hours a year to traffic delays. Nationally, the average commuter wasted 34 hours in traffic in 2009 — up from 14 hours in 1982, the first year for which researchers have records.

The good news, researchers say, is that traffic also is a sign of prosperity.

“The tie between the economy and congestion is not unexpected,” said Tim Lomax, a research engineer with the institute.

Researchers have seen similar regional declines in the past. For example, Lomax said when oil prices plummeted in the 1980s, Dallas and Houston got much-needed relief from traffic as people lost their jobs and stayed home. A similar phenomenon was tracked in California when the high-tech bubble burst in the 1990s, he added.