When the West Falls Church Metro station was built, it was configured to allow a spur to the northwest—-toward Tysons Corner, Reston, and Dulles. Twenty years after the station opened, it looks as if that feature will actually be used. A planned extension, tentatively labeled the Silver Line, would offer service to Tysons by (perhaps) 2012 and Dulles by (maybe) 2015.

But Silver Line advocates haven’t specified where the inbound trains will go after reaching West Falls Church, which is no small issue. So a skeptical Washington Post reader, Tony Battisti, asked Dr. Gridlock what will happen. For his Feb. 25 column, the doctor consulted Steve Feil, the chief of Metro’s rail operations, who said that trains would run from Dulles to downtown D.C. This could work, Gridlock wrote, “with a more sophisticated system of train management than Metro has now.”

Really? Any hint that Metro is anticipating a more sophisticated train-management system is good news, but the Silver Line planners don’t simply mean to add trains to a busy segment. They want to increase traffic on Metro’s busiest rush-hour line, the Orange, sending the additional trains through the system’s acknowledged “choke point,” the tunnel between Rosslyn and Foggy Bottom stations.

Here’s what Jim Hughes, Metro’s planning director, told the Post for a story that ran April 15, 2005: “We’re at the point where we’re putting five pounds of trains through a four-pound tunnel.” According to that article, a 2001 study concluded that the tunnel would be at or over capacity by 2020.

It’s no great relief that some unnamed Metro officials disagreed with that date, arguing that the tunnel wouldn’t be completely stuffed until 2025. In the context of expensive public-works projects, five years is barely a breather.

Sooner or later, another rail crossing will be built between Rosslyn and Washington. Why not sooner? That’s an easy one: Because the elected leaders on the D.C. side of the river haven’t shown any leadership on transportation issues in decades.

When its design team was winding down in the early ’90s, Metro floated ideas for extensions. The big one was a notion that had been discussed before: a new crosstown route from Fort Lincoln to Georgetown, roughly paralleling the Blue/Orange line, but to the north. The tracks would touch the eastern end of New York Avenue corridor, burrow under H Street NE and the northern side of the expanding downtown, and then end somewhere near Wisconsin and M. One of the most interesting aspects of the proposal was that the new line would serve a downtown rail yard under the old Convention Center site. This yard would allow Metro to store a significant number of cars underground in case of snow or ice, and to dispatch trains more quickly to downtown segments in case of emergency.

This all makes sense, except for the end points. It’s unclear where the eastern terminus of the line should go, but with the Silver Line a live possibility, the western end of the crosstown link ought to connect with it, via a new tunnel from Georgetown to Rosslyn. This would not only reduce crowding in the existing tunnel, but also provide another option across town and into Virginia when the Blue/Orange Line snarls.

Would this be expensive? Of course. But such projects are not going to get any cheaper over time, and if the city really intends to foster hundreds of new office buildings, thousands of new commuters, and 100,000 new residents, it will have to expand its rapid-rail system. Buses and streetcars that compete with growing auto traffic—-encouraged by all those parking garages under all those new buildings—-won’t cut it.

Northern Virginia’s enthusiasm for the Silver Line could be a significant asset. If D.C. and Virginia work together, maybe some longstanding financing issues—-like a regionwide source of operating revenue—-could be settled. With a Democrat now running Maryland’s government after the Ehrlich aberration, a return to tri-state coordination might even be possible. (After all, the conjectured New Carrollton-to-Bethesda Purple Line should extend across the river to Tysons.)

Of course, certain prominent city politicians don’t like to put major capital funds into any project that doesn’t include luxury boxes overlooking the action. But that can be handled easily enough. Just build a box overlooking the new downtown railyard, and Jack Evans and his campaign contributors can have hors d’oeuvres and watch the trains shuttle from track to track. It’s sure to be more entertaining than the Redskins.