It comes as no great surprise that it was cold in Boston on a recent Thursday morning. But little did the 1.1 million daily riders of the region's Massachusetts Bay Transportation Authority (MBTA) realize just what a long morning was going to result from the single-digit temperatures. A broken rail forced subway riders onto shuttle buses, and more than one-quarter of the MBTA's commuter trains were delayed by mechanical and other problems.

In retrospect, the surprise wasn't the rush-hour mess, but the fact that such chaos isn't more common. More than half of the MBTA's commuter-rail trains and coaches are at or near the end of their useful lives, and the percentage is even higher for the subway system's rolling stock.

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The hand-wringing that is necessary before elected officials act has been going on for years. In 2007, a commission appointed by state leaders pegged the Massachusetts 20-year transportation funding shortfall at between $15 billion and $19 billion--and that was just to maintain existing assets.

Massachusetts is hardly alone. A number of states are considering hiking fees, gasoline taxes or other levies. Last year, Pennsylvania Gov. Tom Corbett said his state's transportation needs were too large to be handled within the state's budget. "Transportation must be confronted as its own distinct and separate topic," he said.

The time for action finally appears to be at hand. In return for approving a short-term MBTA bailout last year, legislative leaders gave Gov. Deval Patrick a deadline of this month for developing a plan to fix the commonwealth's transportation network. Assuming the needed revenue materializes, the question becomes how to spend it. The Boston Globe reports that Patrick's plan is "expected to spell out how much it would cost to address a vast maintenance backlog and fund strategic expansion projects."

No state should understand better than Massachusetts the need to address maintenance before embarking on expansion plans. In 1991, state officials agreed to build 14 new transit projects as mitigation for less-than-certain environmental damage resulting from additional traffic that Boston's now-legendary "Big Dig" highway project would support. As a result, Boston, one of the nation's slowest-growing metropolitan areas, has for the last quarter-century had its fastest-growing transit system--with no new revenue source to support any of it. Nearly half the MBTA's $8.6 billion debt can be traced to the cost of building, operating and maintaining the projects. So can much of a more than $3 billion maintenance backlog--the legacy of funds being diverted to expansion as maintenance needs were increasing.

After years of refinancing its debt, the bill for all this is coming due. Annual debt-service payments that were $342 million in 2009 will spike to $525 million by 2014. Until a recent fare hike, the MBTA paid more in debt service than it collected in fares.

There are ways to ensure that Massachusetts doesn't repeat its mistakes. Utah, for example, prohibits funding new projects until sufficient money has been appropriated to maintain existing assets. If Massachusetts can get its maintenance backlog under control and begin to invest in expansion, cost estimates for those projects should be based on lifecycle expenses, not just on what each project costs to build.

There can be little doubt about the need for investment in our transportation infrastructure. But unless maintenance needs are addressed before new expansions are undertaken, it won't be long before commuters around the country will be experiencing their own versions of Boston's cold Thursday morning.