After the Metropolitan Council's curious discovery last week that, well gosh, the Southwest light-rail line will cost an extra $341 million because of swampy ground and other unexpected complications on the line's far end, the temptation might be to pull the plug on the entire mess. Gov. Mark Dayton called the overrun "appalling," and who could disagree?

But despite all the acrimony over costs, delays, routing, and now what looks like engineering ineptitude, calling it quits on light rail in the corridor, or converting it to a rapid bus line, would be the wrong thing to do. Here's why:

This is a megaproject aimed at the long term. Twenty years from now, no one will remember the cost. Even so, there's a good chance that the overrun can be erased by, among other things, lopping off the last three stations, at least temporarily. That would trim the route from 16 miles to 12 while restoring the project's momentum, keeping the jobs-intensive stops at Opus and Golden Triangle and preserving light rail's considerable advantages over other modes. What are those advantages?

• While more expensive initially, light rail is cheaper to operate than bus rapid transit and, in most cases, cleaner to run. It draws more riders (up to 50 percent more on similar routes), while offering greater capacity, comfort, speed and reliability.

• Its greatest advantage is as a catalyst for adjacent development. More than other modes, light rail offers a transit-biking-walking alternative that appeals to a growing number of people searching for ways to minimize driving, whether for reasons of health, convenience or environmental concern. It is, in other words, not just a transportation mode, but a lifestyle choice that can compete alongside the market's juggernaut (also heavily subsidized): the car.

• Because of its appeal to young people, light rail and its denser lifestyle is an important competitive draw for the Twin Cities, a market that needs an influx of newcomers to fill a looming labor shortage. To that end, a healthy urban core is essential — and keeping that core within easy reach of a region's most affluent suburbs (in this case, in the southwest) is critical.

• Light rail's extra appeal to discretionary transit riders is important for political reasons. Opponents like to portray transit as a "social service" for those who cannot afford to drive, but light rail's appeal to middle-class riders — especially in the suburbs — gives the entire transit system a broader base of support.

• As an extension of the Green Line, Southwest significantly expands the Twin Cities' system, providing suburban riders single-seat service to the University of Minnesota as well as sports and cultural events in both downtowns, and, more important, easier access to the region's fast-growing southwest job market for city people who need those jobs the most.

"All options are on the table," Met Council Chairman Adam Duininck said last week. But light rail remains the best option for the Southwest line, even if it's a bit shorter.

Steve Berg is a Minneapolis writer and urban-design consultant.