Mica says his “back of the envelope” calculation shows that the TIFIA increase, project acceleration and other provisions would bring his proposal's $38.3-billion average annual authorization to a value of about $75 billion per year. However, Rep. Peter DeFazio (Ore.), a senior Democrat on the transportation panel, dismisses Mica's estimate as “fantasy funding.”

DeFazio and other Democrats, who claim they were excluded from helping to draft Mica's plan, contend it would result in the loss of more than 490,000 jobs, many in construction. The House committee's ranking Democrat, Nick Rahall (W.Va.), said, “It appears that this bill can best be described as the Republican road to ruin.”

The debate is just starting. “I think we have to recognize that we aren't even to the first inning yet,” says David Bauer, American Road and Transportation Builders Association senior vice president for government relations. “The good news is that, clearly, you have two committee chairmen who are dedicated to moving this process forward,” Bauer adds. “At this point, they're both crafting a product that they think has the best chance of getting through their respective chamber.”

Key questions remain, he observes. Will House moderates endorse Mica's cuts, or will conservative GOP freshmen reject his spending level as too high? In the Senate, where Democrats need a few GOP votes to pass a filibuster-proof bill, will Republicans support Boxer's effort to find the $12 billion she seeks?

Steve Hall, the American Council of Engineering Cos. vice president for government affairs, says, “I think it is probably a best-case scenario that we try to level-fund the program.” However, as more details emerge about the plans and lawmakers see how much—or little—funding their states or districts would get, Hall says, “I think that helps to create some positive pressure on trying to find new sources of funding.”

Lawmakers must move quickly. Highway and transit programs have operated under a series of extensions since Sept. 30, 2009, when SAFETEA-LU expired. The latest stopgap runs out on Sept. 30.

With the House and Senate far apart, little progress on a bill is likely before the August recess, says Brian Deery, senior director of the Associated General Contractors highway and transportation division. That possibility would leave less than a month before the Sept. 30 deadline and probably prompt another extension.

If Obama and Capitol Hill leaders strike a debt-limit, deficit-reduction deal, it may cause Mica and Boxer to revise their numbers. Deery says, “To me, there's just an awful lot of uncertainty out there.” He says if the eventual bill maintains current transportation funding levels for the next fiscal year or two, “I think that would be a tremendous victory for us all.”