A new report has quantified gridlock and ranked the traffic delays experienced in the Bay Area and Los Angeles as equal. The Urban Mobility Report, produced by the Texas A&M Transportation Institute, placed the 61 hours of annual delay experienced in the two California metropolitan areas as second worst in the country, behind Washington DC’s 67 hours.

Using a scale called the Planning Time Index, researchers measured reliability in travel, which can then illustrate how much “extra” time travelers plan to accommodate time-sensitive events.

“Researchers now have a way to measure that degree of unreliability,” reads a release issued by the research team at Texas A&M. “If the PTI for a particular trip is 3.00, a traveler would allow 60 minutes for a trip that typically takes 20 minutes when few cars are on the road. Allowing for a PTI of 3.00 would ensure on-time arrival 19 out of 20 times.”

Rankings of the nation’s most congested cities vary slightly from year to year, and many of this year’s top 10 are repeat performers. Washington, D.C. tops the list, followed by Los Angeles, San Francisco-Oakland, New York-Newark and Boston.

“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,” says  Bill Eisele, a TTI researcher and report co-author. “As bad as traffic jams are, it’s even more frustrating that you can’t depend on traffic jams being consistent from day-to-day. This unreliable travel is costly for commuters and truck drivers moving goods.”

The total financial cost of congestion in 2011 was $121 billion, up one billion dollars from the year before and translating to $818 per U.S. commuter. Of that total, about $27 billion worth was wasted time and diesel fuel from trucks moving goods on the system.

Fuel wasted in congested traffic reached a total of 2.9 billion gallons – enough to fill the New Orleans Superdome four times. That’s the same as 2010, but short of the 3.2 billion gallons wasted in 2005.

In addition to PTI, the 2012 UMR also debuts an estimate of the additional carbon dioxide (CO2) emissions attributed to traffic congestion: 56 billion pounds – about 380 pounds per auto commuter.

Researchers say that the most effective way to address traffic congestion varies from one urban area to another, but that in all cases, a multi-faceted approach should be used, relying on more efficient traffic management and public transportation in addition to new construction. Travel options such as flexible work hours and telecommuting should also be part of the mix.

The 2012 installment of the study includes 30 years of trend data with which TTI has measured and analyzed traffic congestion and its impact on life in urban America. The report is the third prepared in partnership with INRIX, a leading private-sector provider of travel time information for both commuters and shippers.

TTI, a member of The Texas A&M University System, seeks solutions to the problems and challenges facing all modes of transportation, as well as helping prepare students for transportation-related careers.