Given how much Metrorail can transform a community, it’s little wonder communities want it to reach them. But planning and building new Metro lines is so politically and technically complex that it takes decades. Consider the Silver Line:

Slide from WMATA.

This slide showing a timeline of Silver Line planning and construction comes from a presentation WMATA planners Allison Davis and Kristen Haldeman gave at StreetsCamp this past Saturday.

The timeline begins in 1985, when the idea of a Metro line to Dulles Airport went from vague concept to serious planning initiative following a study that determined it would be feasible.

Planning (yellow on the timeline) and environmental work (green) took the next 21 years, until 2006. It took another 3 years for officials to finalize funding (blue) before construction (purple) could begin in 2009.

By the time the last segments open in 2019, it will have been 34 years.

Worth the wait, no doubt. But there’s bad news for other communities:

Silver Ln was the easiest possible line to build. Only in VA, above ground & we already had right-of-way. Still took decades. #streetscamp

— BeyondDC (@beyonddc) June 20, 2015

Plopping a rail line down the middle of a gargantuan suburban highway with a capacious median is easy compared to putting one virtually anywhere else. Almost any other potential Metrorail expansion imaginable will be harder to plan, fund, and build.

That doesn’t mean it’s not worth doing. But it’s definitely going to be hard.

 Cross-posted at Greater Greater Washington.