Now that the Silver Line has opened (finally), let’s think about what other ambitious transportation projects our region should undertake as we try to relieve some of the nation’s worst traffic congestion.

I’ve got two.

The first is urgent but unsexy: The Washington area needs to come up with enough money, and soon, to buy Metro about 200 rail cars so it can use eight-car trains instead of six-car ones during rush hour.

The second proposal is long-term but controversial, especially in Maryland: The region needs to start planning to add a Metro tunnel, a highway bridge, or both, to make it easier to cross the Potomac.

I raise this in hope that the Silver Line’s debut will reassure us that vision and persistence can overcome severe obstacles — and these proposals will face plenty.

Metro’s Silver Line rumbled to life Saturday as five new stations opened in northern Virginia. (Lee Powell/The Washington Post)

As U.S. Rep. Gerald E. Connolly (D-Va.), a longtime Silver Line champion, put it, “getting big things done is not for the faint of heart.”

The Silver Line nearly died multiple times. It required numerous compromises and overcame staunch anti-transit sentiment in parts of the George W. Bush administration. Ultimately, financing was guaranteed only by raising tolls on the Dulles Toll Road to ridiculously high levels.

Now the region needs to apply the same tenacity (if not the excessive tolls) to expanding Metro’s capacity, and adding a Potomac crossing (or two).

These aren’t the only needs requiring attention, of course. Others include the Purple Line, the Capitol Beltway inside Montgomery County and street cars (or alternatives) in Arlington and the District.

But the big region-wide challenges are the two I mention, as the area wrestles with how to absorb 2 million new residents expected to arrive in coming decades.

The Silver Line means increased Metro ridership, which adds to the need for eight-car trains. They also are necessary to relieve the burden on congested stations including L’Enfant Plaza, Gallery Place, Metro Center and Rosslyn.

The governors of Maryland and Virginia, and the District’s mayor, pledged in February to support the expansion in principle. But they and local jurisdictions are showing signs of balking at actually cutting the checks, which will total more than $1.5 billion over five years.

State and local governments need to commit to the funding in less than a year, or Metro will have to renegotiate contracts with the train car supplier. That would delay the whole project by at least five years.

Practically everybody involved in transportation — pro-transit and pro-highway, business and labor — agrees that investing in eight-car trains ought to be the region’s No. 1 priority.

Top local business groups have formed the 8carcoalition to build public support for the funding. It has prepared an amusing ad showing white-gloved Tokyo transit officers pushing passengers into an already packed train, and asking, “Is this the solution for overcrowding?”

Looking farther ahead, adding a Potomac crossing, or at least widening the American Legion Bridge, is emerging as a top challenge for the region.

The American Legion span, on the western side of the Capital Beltway, is now one of the area’s worst bottlenecks. But it’s the only route to connect the region’s two biggest counties, Fairfax and Montgomery.

“The looming nightmare of the American Legion bridge cannot be overstated,” said Jim Dinegar, chief executive of the Greater Washington Board of Trade.

Connolly said, “Sooner or later, this region has got to have another river crossing. . . . We can’t just keep our heads in the sand about this.”

The multibillion-dollar question is where.

Metro wants to build a tunnel from Rosslyn to Georgetown. Transit advocates would like to see light rail or express buses across a rebuilt American Legion bridge.

Some in the business community, especially in Northern Virginia, hope to revive proposals to add a highway bridge north of the American Legion span.

“If you could do one thing that would take traffic off other corridors . . . that would be it,” said Bob Chase, president of the Northern Virginia Transportation Alliance.

Maryland consistently has vetoed an up-river bridge. Environmentalists object and there’s considerable opposition in western Montgomery County — where a bridge would presumably be located — and in parts of Northern Virginia.

Supporters hope the next Maryland governor will be more sympathetic.

The two states and the District need to find a way to add at least one crossing — Metro or highway — and expand capacity of the American Legion bridge. And the region should ante up to buy Metro the new cars.

Don’t let the Silver Line’s good example go to waste.

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