An excavator loads the contents of a salvaged coal seam unearthed during the construction of a new segment of U.S. Highway 460, part of the Appalachian Development Highway System, into a dump truck near the Virginia border in Elkhorn City, Kentucky, U.S. on Tuesday, July 22, 2014. Senate Democrats may bring to the floor a House-passed measure that would replenish federal funds for highway and mass-transit projects through May 2015. As part of that debate, senators could vote on two Democratic alternatives, although leaders say the House measure is more likely to prevail. (Luke Sharrett/Bloomberg)

FIRST THERE was the “fiscal cliff”; now congressional dysfunction has brought the country to the edge of the “highway cliff.” Federal money needed for the nation’s roads and rails will begin disappearing Friday if lawmakers refuse to act. This crisis may not have the same stakes as the fiscal cliff, but it is just as unnecessary. It stems from the same problem: Too many members of Congress are too cowardly or too shortsighted to accept the viable solutions in front of them.

At first glance, you might blame the standoff on the Senate. The House passed a plan this month that would provide enough cash to push the problem off until next May or so, at which point lawmakers might have sorted out a long-term funding plan for the perpetually strapped Highway Trust Fund. All the Senate had to do was agree to the measure and move on. Instead, senators approved a proposal from Sen. Barbara Boxer (D-Calif.), Sen. Tom Carper (D-Del.) and Sen. Bob Corker (R-Tenn.) that would provide funding only through December. The Senate also insisted on paying for its shorter patch with a different combination of revenue sources. House Speaker John Boehner (R-Ohio) responded that the House wouldn’t accept the Senate’s version. Stalemate, once again, at the edge of a policy cliff.

In fact, the Senate’s plan is better — though the two chambers are arguing over fairly small differences. Neither plan represents a long-term fix to the nation’s transportation funding program. Both rely on accounting maneuvers to top up the Highway Trust Fund for a relatively short period of time. The two main differences are that the Senate’s accounting maneuvers are more palatable and that its version gives less time for irresponsible stopgaps to fund the country’s transportation budget.

That’s good: Congress does not need more time to determine how to fix the Highway Trust Fund. Lawmakers simply need to drum up the willingness to expand the sensible funding mechanism their predecessors established decades ago: the gasoline tax. Gas tax revenue is devoted to transportation projects, which makes sense. Those who use the roads should pay for them. But Congress hasn’t increased the gas tax in two decades. The simple, efficient solution for the Highway Trust Fund is to raise the gas tax and index it to inflation, which would shore up the fund for a long time. Mr. Corker and Sen. Chris Murphy (D-Conn.) have already introduced a proposal to do just that. If Congress doesn’t pass it now, it should do so immediately after the November elections, when lawmakers will have less reason to pander to constituents.

That’s the reason to support the Senate’s shorter-term patch, which would force a transportation debate in this Congress’s lame-duck session. House leaders instead want to pass their original bill anew and force the Senate to accept it. If House Republicans want to quibble over how the patch is funded, fine. But they shouldn’t insist on kicking the can any farther down the road than the end of the year.