The underlying principle here is that big investments ought to be based on forecasts—whether of future traffic or ridership—that fully reflect all the information we have at hand on how travel patterns are changing, and are likely to change in the future.Unfortunately, this is an overly optimistic interpretation of the ruling, in my view. I'm all for more realistic forecasting methods, but there's little evidence in this case that MTA or FTA should have done anything differently.
While it's true that DC Metro transfers are predicted to account for about a quarter of the Purple Line's ridership, let's game this out: assuming current trends continue, Metro ridership will be about 10% lower than its 2009 level by the time the Purple Line opens in 2022.
So: 25% x 10% = 2.5% difference from the current forecast. Significant, sure, and something to plan for, but hardly an earth-shattering difference.
And that's a very generous assumption for the plaintiffs. For one thing, it's quite possible that Metro's woes would actually increase Purple Line usage, since a new light rail line is likely to be a far more reliable option.
And, as mentioned, the Purple Line's projected opening is six years in the future. (And keeps getting delayed by lawsuits like this.) It's highly unlikely that Metro will still be in such bad shape by then.
It's a very different situation than relying on clearly outdated traffic models, where courts have shown every deference to state DOTs, even in the Wisconsin case mentioned (which was a very narrow ruling).
For context, Friends of the Capital Crescent Trail is a NIMBY group based in a wealthy suburb, Chevy Chase, that has opposed the Purple Line since its inception for reasons that have nothing to do with ridership forecasts.
For years, they've thrown every legal argument at the wall hoping something would stick -- declaiming the effect of the project on their namesake trail, mainly, even saying that danger to a rare arthropod should scrap the whole project.
What this ruling really says is that they've found a judge who finally bought one of their capricious arguments. A judge who happens to live in Chevy Chase and is a member of a country club that is vehemently opposed to the Purple Line, for that matter.