WITH THE Highway Trust Fund running dangerously low on cash, threatening infrastructure projects across the country in the height of construction season, members of Congress seem to have settled on their latest short-term gimmick to pay for the country’s roads and rails. The only question left seems to be when they will try to do something better. The answer should be: immediately.

Without new funding, the Transportation Department will begin slashing highway payouts to states starting Aug. 1. Few want to see that, but lawmakers have been perpetually unable to fund the nation’s transportation budget responsibly. So, depressingly if predictably, with another funding crisis looming, members of Congress seem to agree on exploiting an arcane accounting trick called pension smoothing, which could reduce the security of private pensions but would result in more federal revenue over a decade. That decade’s worth of revenue will pay for several months of transportation spending.

This budget gimmickry is distasteful for several reasons, starting with the fact that the plan spends money now, over the course of less than a year, that the government will make back over 10 years. The idea is to give Congress more time to sort out a permanent solution to the Highway Trust Fund’s perpetual funding shortfalls. But lawmakers don’t need more time; they need more spine.

The straightforward policy, the one on which the Highway Trust Fund historically has been based, is to raise the gas tax to keep up with inflation and infrastructure needs. This model is fair and efficient, demanding that those who use the roads pay for them. As a sustainable and predictable source of revenue, a gas tax of sufficient size also would eliminate uncertainty about the level and source of government transportation funding.

Congress could end the transportation funding crunch by adopting a bipartisan plan from Sen. Bob Corker (R-Tenn.) and Sen. Chris Murphy (D-Conn.). The proposal would raise the gas tax by 12 cents per gallon over two years, and it would index the tax to inflation. The last time Congress raised the gas tax, in 1993, it failed to peg the tax to inflation, which is largely why lawmakers are scrounging for money now.

Lawmakers should pass the Corker-Murphy plan. Instead, they are fighting over when they will have to consider the long-term transportation funding issue. Many Republicans want to push off the decision-making until next spring. Many Democrats want to have the debate this December. If lawmakers aren’t willing to accept the obvious funding plan in front of them before the November elections, they should do so immediately afterward, when the political atmosphere may be more conducive to doing the right thing. More important, there’s no reason to make the country wait any longer for funding certainty.