The time-and-venue change for Sen. Barbara Boxer’s press conference earlier today was apparently due to the fact that she was taking care of critical business: hand-delivering the Senate’s latest offer to the House Transportation and Infrastructure Committee. Chair John Mica (R-FL) wasn’t there to personally receive the document, which EPW Ranking Member James Inhofe joined Boxer in delivering, but the submission is a significant step in the conference process. If the two houses can’t come together on a conference report — with the Senate offer being a first draft — the Highway Trust Fund’s solvency is at stake, with potentially serious consequences for key programs.

Senate sources wouldn’t get into the details of the policy proposals in the offer, but said that it “moves in the direction of the House.” We’ll have to wait and see what that means for bike/ped funding, which some House Republicans want to eliminate, and for the controversial anti-environmental amendments the House is insisting on.

The Senate’s offer included the highway, transit, and rail/safety titles but not the finance piece. Ongoing discussions about the length of the bill make it impossible to put a dollar figure to it just yet. Sources say the bill will be at least as long as MAP-21, the Senate bill which would run through next September, but it could be longer, if the pay-for can be agreed upon.

It’s up to the House now to come back with its counter. It’s the job of the conference committee to iron out all the differences between the document Boxer and Inhofe sent to the House today and whatever the House sends back.

Meanwhile, the stakes couldn’t be higher. While many stakeholders and lawmakers focus on the millions of jobs that this bill could create or save, especially in the devastated construction sector, the bigger issue is the solvency of the Highway Trust Fund. Lawmakers passing extension after extension have made the problem far worse. At this point, the Highway Trust Fund is expected to run out of money around the end of this year.

Current law doesn’t address this problem. The Senate bill pays for itself until September 2013, when the issue will arise again. But if the trust fund is simply allowed to go bankrupt, through Congress’s inaction, it could intensify pressure to eliminate certain programs. They won’t be the programs that really cost the Trust Fund money — massive road-building, for example — but rather the hot-button, small-slice issues that have caused so much heartache already in these proceedings: bike/ped and transit.

Many have speculated since before the conference even got underway that no bill would come of it. This scenario makes the “no bill” option a grave one — potentially even worse than the passage of a highly problematic bill, even one with some of the “poison pills” included by the House.

If the conference committee can’t come to an agreement and get a new bill signed into law by June 30, active transportation advocates could find themselves playing defense against an ever-louder chorus calling for the shutdown of important funding programs that the highway lobby has long tried to get rid of.