Among those provisions are steps to consolidate the dozens of current surface-transportation programs into a smaller number, accelerate project delivery time and merge current freight-transportation programs.

The plan also calls for eliminating earmarked funding for specific projects.

A key part of the package is a significant expansion of the 13-year-old Transportation Infrastructure Finance and Innovation Act program(TIFIA), which provides federal loans and loan guarantees to help finance major  projects.

Boxer says that under the agreement, direct federal funding for TIFIA would jump nearly tenfold, to $1 billion a year, from $122 million in 2010.  The amount of TIFIA-assisted project loans would be about $10 billion annually, because each dollar of direct federal TIFIA subsidies supports $10 worth of loans.

Boxer indicates that the bill's six-year time frame isn't etched in stone. She says a shorter span is possible, depending on what funding actually is available.

"We are hoping for a six-year bill. We may not wind up with a six-year [bill]." she says.

Baucus has floated the idea of a two-year reauthorization, noting that the Highway Trust Fund's currently projected revenue would support a highway program of about $42 billion a year for only that long. If
the fund's revenue were spread over six years, the says, he annual amounts would have to be cut to $28 billion.

An infrastructure bank is not part of the current agreement, but Boxer says such an entity could be included later.  Two infrastructure bank-type proposals have been announced recently in the Senate.