Everyone knew what was coming, but the options that the Congressional Budget Office presented Tuesday to resolve the nation’s transportation funding crisis laid out a grim reality for lawmakers in this election year.

“It’s an American characteristic that you can’t do anything to displease the voters,” said Sen. John D. Rockefeller IV (D-W.Va.), who felt free to speak candidly because he’s not seeking reelection.

The choices that the CBO’s Joseph Kile spelled out to the Senate Finance Committee were not the kind that are likely to please voters.

Kile said Congress could reduce spending on roadways by 30 percent and on transit by 65 percent. To avoid that, it could raise the 18.4-cents-per-gallon federal tax on gasoline by 10 to 15 cents per gallon. Or it could transfer $18 billion from the general tax fund to prop up the pool of federal money that pays for roads and transit.

“Failure is not an option,” said Sen. Barbara Boxer (D-Calif.), who testified before the committee. “It’s our time to figure this out.”

Boxer’s Environment and Public Works Committee is busy crafting a plan for transportation spending that should emerge late this week. It’s said to be a six-year proposal that keeps funding at the current level, adjusted for inflation.

But it falls to the Finance Committee to come up with the money to pay for it all, and where to find that money is a multibillion-dollar question. The traditional source, the Highway Trust Fund, relies primarily on gas and diesel taxes — which have not been increased since 1993 — and no longer are enough to pay the bills in an era of increasing fuel economy.

The trust fund won’t be able to meet its obligations by August, according to federal projections, turning off the spigot for state projects across the nation.

“Congress needs to find a sustainable source of funds that keeps this crunch from happening again,” said Senate Finance Committee Chairman Ron Wyden (D-Ore.).

With Transportation Secretary Anthony Foxx scheduled to appear Wednesday before the third Senate committee that has a hand in the game — Rockefeller’s Transportation Committee — and the House prepared to take up its own transportation bill, there was plenty of movement, but it seemed premature to call it momentum.

Funding for the current transportation bill was patched together at the last minute by using several one-time pools of cash to augment the already deficient trust fund. With that bill expiring Oct. 1 and the fund running into the red a couple of months before that, states fear that they won’t be able to count on Washington to come up with the money they need.

“We’ve certainly looked at what happens if the federal government doesn’t give us any money, and it’s pretty dire,” Virginia Transportation Secretary Aubrey L. Layne Jr. told the committee.

He said Virginia relies on the federal government for about half of its transportation capital spending.

Committee members discussed a variety of other funding options, including expanded tolling and charging drivers for each mile they travel. Notable among the options was getting private companies to invest in public infrastructure, in private-public partnerships commonly referred to as P3s.

While Kile said such partnerships have had a minimal impact, and Layne called them useful for about 15 percent of the state’s projects, Jayan Dhru of Standard & Poor’s estimated private U.S. investment in infrastructure could amount to $100 billion.

“While in the U.S. P3s are still relatively new, elsewhere in the world they are being used more extensively to build public transit, airports, schools and hospitals,” Dhru said.