Metro mayors plan to look at RTD's over-budget FasTracks program with a "trust but verify" attitude toward the transit agency's claims of soaring costs and the need for more money.

"Our constituents would want us to take an independent look at this and not just rely on RTD's version of things," said Lakewood Mayor Bob Murphy, who is heading a task force of the Metro Mayors Caucus working on the FasTracks budget crisis.

At a meeting with RTD on Monday, mayors and representatives of eight cities discussed coming up with $35,000 to hire experts who, along with some volunteers, would sift through RTD's claims. The transit agency says spiking construction costs have driven FasTracks $2.1 billion over budget, forcing either a tax hike or a slashing of plans for light rail.

Murphy said it's not that the mayors don't trust RTD. Rather, they want to be able to face the public and say they've done their research.

Thirty-seven cities and towns belong to the group.

At the meeting, mayors from the north and east metro area blistered RTD over assuming that some FasTracks rail lines should be fully built while cutting back those serving their communities.

"There are too many sacred cows in this room," said Thornton Mayor Eric Hansen.

RTD says with rising construction costs and other factors escalating FasTracks to $7.9 billion and the souring economy limiting its financing to $5.8 billion through 2017, it must find an equitable way to trim some projects while still building three of the 10 proposed transit corridors completely.

That's because those three - the West Corridor light rail, East Corridor to Denver International Airport and Gold Line to Arvada/Wheat Ridge - qualify for federal grants. RTD would lose the federal assistance if it scaled those back.

When RTD showed options that would extend existing south metro light rail lines a short distance to Littleton and Douglas County, north and east metro mayors objected strongly to the notion that the plan was fair.

"I just have a serious problem with that approach," Hansen said. "There are already lines down in that direction. They already can take light rail downtown . . . This is not a numbers problem; this is a political problem for the whole metro area."

Broomfield Mayor Pat Quinn agreed.

"Our corridor (U.S. 26 and Northwest Rail) basically subsidizes the East Corridor. So now, $800 million our voters expected isn't going to come to our corridor, and that's a political problem," Quinn said.

Bill Vidal, Denver deputy mayor and public works manager, said the only truly fair solution is to find a way to build all 10 corridors completely, as the original plan voters approved four years ago spelled out.

But that likely would entail asking voters for another increase in sales tax.

Aurora Mayor Ed Tauer said the problem is some corridors getting everything that was promised because they get federal assistance while other parts of the metro area have to stand in line again.

"Nobody's saying 'Let's walk away from federal dollars,' but at the same time how does Pat (Quinn in Broomfield) go back to his constituents and say this is OK?" Tauer said.