In the beginning, House Republicans wanted a six-year transportation bill for highways, bridges and transit. Something long-term. Something to end Congress’s addiction to short-term spending bills that leave states unable to plan. (Congress has passed eight such stopgaps since 2009.)

A sinkhole can form when a pothole expands beyond the boundaries of the roadway and dirt begins to erode below the surface. (District Department of Transportation)

Quite a bit. Transportation experts have long argued that Congress’s barrage of stopgap and short-term bills since 2009 have made it harder for states to do any sort of rational planning. “States are required by the federal government to develop long-term transportation plans,” writes Paul Yarossi of HNTB Holdings. “Yet we are potentially looking at much shorter-duration authorization bills.” Even the Senate’s two-year $109 billion bill, which maintains current funding levels, is less ideal than a longer-term bill.

But even that two-year bill is up in the air. The Senate is debating a number of controversial amendments to its highway bill, on things like approving the Keystone XL pipeline. If Congress can’t agree to this legislation and has to revert to more two-month extensions, a number of transportation projects will remain in limbo. Bloomberg’s Jeff Plungis takes stock of endangered projects across the country, including a plan to extend train lines in Los Angeles out to UCLA and the I-15 highway connecting Las Vegas to California. As Harry Reid put it in a call with reporters last week, “Try getting a two-month contract to do a construction job on I-15.”

Of course, a two-month extension is still better than letting funding run out entirely. Politico’s Adam Snider and Burgess Everett document the carnage that would result if March 31 rolls around and Congress has done absolutely nothing. States would no longer be allowed to spend money in the Highway Trust Fund. Not only would mass layoffs in the construction industry ensue, but in many cases, costs would actually go up: “Construction firms can charge states a ‘demobilization’ fee for halting work and a ‘mobilization’ charge when they resume.” True, it seems preposterous that Congress would simply allow highway spending to expire, but consider that the Federal Aviation Administration endured a two-week partial shutdown last summer when Congress couldn’t agree on funding.

On the other hand, not all transportation experts are convinced that more stopgaps are the worst outcome in the world. In a National Journal forum, Deron Lovaas of the Natural Resources Defense Council argued that plenty of previous highway bills have been preceded by stopgaps. A more important priority, he notes, is developing legislation that focuses on setting smart national priorities rather than simply funding highways willy-nilly, as past bills did. The Senate extension, for its part, basically continues past policy with a few tweaks.

In other words, waiting a bit for a better bill to emerge might be worth all the havoc caused by temporary extensions. But what would a better bill look like? See this old post for some ideas on how to improve the way we do transportation spending.