In 2004, the Federal Transit Administration concluded that the Dulles Rail project was not cost effective, because population densities in the corridor to be served were less than half those required to support heavy rail. The Metropolitan Washington Airports Authority reacted by splitting the Metrorail extension project into two sections, with only Phase 1 receiving federal funds. But MWAA is now seeking a federal loan under the Transportation Infrastructure Finance and Innovation Act, or TIFIA, to help pay for Phase 2.

Although TIFIA funding is far from guaranteed -- only $750 million is available nationally and the pending requests (including MWAA's) come to $27 billion -- the application opens the door to increased scrutiny of MWAA's highly questionable traffic, revenue and ridership forecasts.

We already know that MWAA's 2009 estimate of employment and population growth in Fairfax County was wildly inaccurate, overshooting the final 2010 census numbers by 52 percent. The pro-transit Reston Citizens Association's 2020 Committee has also questioned MWAA's economic forecasts and is now making some predictions of its own:

* Over the next 40 years, population and employment growth in the Dulles Corridor will be lower than predicted;

* There's a 67 percent chance that MWAA's annual revenue forecasts will not be met, with 25 percent shortfalls possible in 40 years;

* 30,000 vehicles will divert from the Dulles Toll Road to escape exorbitantly high tolls needed to fund Phase 2.

If the RCA is right, employment and growth rates in the Dulles Corridor will be much lower than the levels optimistically predicted by the outdated "Dulles model" from before the Great Recession, before the threat of sequestration and before density downsizing in Loudoun County. That will affect ridership.

The 2004 Final Environmental Impact Statement predicted that in 2025, the project as it is being built "would result in approximately 47,800 new average weekday trips on the system." Since Metro riders generally take two trips daily, to and from work, the absolute best-case scenario has 23,900 local drivers switching to the Silver Line within the next 13 years. But they will be eclipsed by the 30,000 drivers the RCA estimates will crowd onto those same local roads to avoid the punishing tolls needed to pay for the Silver Line.

There is only one word for a project that costs $2.7 billion and creates more traffic congestion rather than less: insane. The FTA got it right the first time. The feds should spend scarce TIFIA funds on projects that make more economic sense.