The transit agency is seeking more than $13 million in the lawsuit filed against Lexington in U.S. District Court for the Eastern District of Virginia.
The suit says the agency has yet to pay for "a drastic drop in rail ridership and consequential loss of revenue" caused by the June 22, 2009, crash.
The Red Line crash killed nine people and injured dozens more. The rail system was hamstrung afterward as investigators studied the crash site and the agency repaired the tracks. But the agency says in the suit the effect was "system-wide," extending beyond the section of track between Fort Totten and Takoma stations where the crash occurred, with delays extending across all lines for months.
Metro calls the loss of ridership substantial, estimating it has cost the agency more than 6 million Metrorail trips. That's the equivalent of about 2.8 percent of all the trips on the rail system in the last fiscal year.
"Those losses continued to at least December 2009 or thereafter and potentially to the present," the suit says, because Metro "still has not been restored to normal operations as a result of the accident."
Metro continues to operate its trains manually as a safety precaution in the wake of the crash and is still replacing the type of track circuits that are believed to have caused one train to slam into the back of a stopped train.
Metro says it paid $1.86 million for the insurance policy that was supposed to cover up to $50 million of coverage per incident, including losses resulting from "partial, complete or potential suspension of business."
The transit agency says Lexington had agreed to cover the crash. But it says the company has paid out only $1.21 million and has yet to agree on how much to pay for eight damaged rail cars.
A Lexington Insurance spokeswoman did not return multiple calls for comment on Tuesday.
Metro spokesman Dan Stessel declined to comment, saying the agency doesn't discuss active or pending litigation.
Transit agency officials initially had shied away from connecting falling ridership to the crash after The Washington Examiner first reported on the drops in August 2009, with one spokeswoman cursing to another news outlet when asked about the story.
It has continued to blame the poor economy and weak unemployment rates as contributing factors to two years of ridership declines on the rail system.
Rail ridership dropped slightly in the last fiscal year, down 166,000 trips, which is less than 0.1 percent drop over the previous year. But it declined by 5.6 million trips that year, or 2.5 percent, from the prior year, according to agency figures. That means rail ridership has not returned to the levels seen before the crash when the agency logged record ridership on its subway system.