With the price of gas heading upward -- an average of $3.54 a gallon -- it might pain Twin Cities motorists to know that they are wasting 12 gallons a year while sitting in traffic. They also spend an extra 34 hours on the road annually due to congestion.

Add it all up and that costs metro area drivers $695 annually, according to the 2012 Urban Mobility Report released Tuesday by the Texas A&M University Transportation Institute.

While the institute's report looking at mobility and traffic congestion on freeways and major streets in 498 urban areas in the United States found that congestion nationwide has remained relatively stable in recent year, congestion on Twin Cities freeways got a little worse from 2011 to 2012.

The Minnesota Department of Transportation said 21.4 percent of freeways Twin Cities are congested during peak periods (6 to 10 a.m. and 3 to 7 p.m. weekdays) compared with 21 percent in 2011.That is up from 17.5 percent in 2008 but down from 21.5 percent in 2010.

"Our study shows that congestion levels appear to be holding its own in the metro area over the past year," said Scott McBride, district engineer for MnDOT's eight-county Metro District. "We have not seen a significant change in congestion between 2011 and 2012."

In recent years, MnDOT has taken steps to reduce congestion by opening MnPass lanes to drivers who pay a fee to drive in lanes reserved for carpools, buses and motorcycles. It also has installed overhead message boards to warn drivers of crashes and congestion and give travel times. It also operates ramp meters to space out traffic and has or is currently rebuilding problematic intersections such as the Hwy. 169-I-494 and I-694 and Hwy. 10 to help improve traffic flow.

The nation's worst roads in terms of rush hour congestion are in Washington D.C., followed by Los Angeles, San Francisco-Oakland, New York-Newark and Boston. Rounding out the top 10 were Houston, Atlanta, Chicago, Philadelphia and Seattle.

In one measure of congestion, the study's authors assigned cities a Planning Time Index, which is a travel time reliability measure that represents the total travel time that should be allowed for trip that would take 20 minutes in free-flowing traffic. The Twin Cities PTI was 3.14, meaning in rush hour motorists should allow about 62 minutes for a trip that normally would take 20.

"We all understand that trips take longer in rush hour, but for really important appointments, we have to allow increasingly more time to ensure an on-time arrival," said Bill Eisele, researcher and report co-author. "As bas as traffic jams are, it's even more frustrating that you can't depend on traffic jam being consistent form day to day. This unreliable travel is costly for commuters and truck drivers moving goods."

Collectively in 2011, the nation's drivers wasted 2.9 billion gallons of fuel, or enough to fill the New Orleans Superdome four times. That was less than the 3.2 billion wasted in 2005, the report said.

The report also found that congestion cost U.S. drivers collectively $121 billion or an average of $818 per commuter. That was an increase from $120 billion the year before. Of the $121 billion, $27 was in wasted time and diesel fuel from trucks moving goods across the country.