MAP-21 also gives a huge funding boost to the Transportation Infrastructure Finance and Innovation Act (TIFIA) program, which provides loans and loan guarantees for major projects. Under the new bill, direct aid to TIFIA would climb to $750 million in fiscal 2013 and to $1 billion in 2014, up from $122 million a year now.

TIFIA is attractive to states, localities and congressional lawmakers because each dollar of direct federal subsidy supports $10 in loan value. Thus, the $1-billion authorized for 2014 would back $10 billion in loans for projects.

Project-approval “streamlining” provisions were in both the Senate- and House-passed bills. The final version moves closer to the House’s language, which was more favorable to industry.

The changes are expected to halve the time for environmental and other reviews and permitting, a House GOP leadership aide says. One provision would have project reviews by multiple federal agencies done concurrently, rather than one after another.

Stephen Sandherr, Associated General Contractors of America CEO, said the measure "provides the kind of serious and substantive reforms needed to make the federal program more cost-efficient and more effective at delivering needed transportation improvements."

But environmental groups contended the project-review provisions go too far. Scott Slesinger, the Natural Resources Defense Council's legislative director, said the final version has "damaging and unnecessary concessions that weaken environmental reviews of highway projects—reducing public oversight and excluding some from review entirely."

Another compromise came over transportation “enhancements,” such as bike paths and walkways, which have enjoyed a mandated share of highway funds.

Republicans had pushed to pull back on enhancements, which, they argued, divert funds from mainstay highway and bridge projects. The final version retains the enhancements program, and renames it "transportation alternatives," but directs half the funds to local agencies. States would continue to determine how to use the other 50% of the money and have more flexibility in how to use it.

Industry officials were happy and relieved to see the bill finally become law. But they also note that it does not provide a long-term prescription for fortifying the weakened Highway Trust Fund, the highway program's main federal funding source since 1956.

The rise of more fuel-efficient vehicles and some slowdowns in miles traveled, because of the economic crunch, have put a crimp in the trust fund's gas-tax income.