While Congress continues to debate a long-term reauthorization of the nation's surface transportation program, the Senate Appropriations transportation subpanel will vote on the Obama administration's six-year, $476 billion proposal tomorrow.

The massive spending plan, included in the fiscal 2013 budget request, has drawn fire on the Hill for its heavy spending and reliance on money saved from the wars in Iraq and Afghanistan. It is largely seen as an afterthought in the authorization game, especially since the Senate has already passed a two-year, $109 billion authorization bill.

However, the president's plan is far more robust than the other options on the table -- the House has discussed a five-year, $260 billion bill, but has made little movement and now appears to be leaning toward a conference with the Senate. In addition to a $50 billion upfront infrastructure boost, Obama's plan includes $47 billion for high-speed rail, $108 billion for mass transit and funding for bike and pedestrian infrastructure.

However, the proposal to dedicate war savings has drawn the ire of some legislators, who have decried it as a funding gimmick that will not actually save any money. Transportation Subcommittee Chairwoman Patty Murray (D-Wash.) questioned that idea at a recent hearing, as well as an administration proposal to reclassify transportation spending as mandatory.

That, Murray said, would leave a "big hole that this subcommittee will have to fill."

Republicans, including ranking member Susan Collins (R-Maine), have also criticized specific spending measures in the bill, particularly a $47 billion investment over six years for high-speed rail and increased spending on livability programs.

Transportation Secretary Ray LaHood has defended it as a solid funding plan, saying it is better than offerings in previous years criticized for not having any pay-for.

LaHood has also publicly lobbied for Congress to take up the president's plan, calling it the best reauthorization option out there, although he has also begun to stump for the Senate's proposal.

Schedule: The markup is tomorrow at 3:30 p.m. in 138 Dirksen.