Metro, which operates trains buses and parking garages in and around Washington, D.C., is losing roughly $400,000 from its receipts for every business day that the partial government shutdown persists.

That revelation from WMATA General Manager and CEO Paul Wiedefeld came in a letter to the Democratic senators from Maryland and Virginia who represent many users of the Metro system, including federal employees.

“Our preliminary analysis estimates that for an average weekday when the government is closed, Metro is losing approximately $400,000 in fare and revenue,” Wiedefeld wrote.

And the WMATA leader said the situation could get worse in the coming weeks because of the way employer-based commuter benefits are transmitted by the federal government to its workforce.

“As you know, federal employees are eligible to receive transit benefits (SmartBenefits) from the federal government to subsidize their use of Metro for their trips to and from work,” Wiedefeld wrote. “We have been advised that if the current shutdown is not resolved by January 21, many affected agencies will be unable to distribute February SmartBenefits to participating federal employees.”