Thousands of connections in signal systems will need to be cleaned and tested before trains can run again, said Mortimer Downey, a former MTA executive director and current board member of the Washington Metropolitan Area Transit Authority.

“It’s an enormous amount of wiring and an enormous amount of connections that go to what’s called relay rooms,” Downey said. “They’ve got to turn the system on, and if it seems to be working I think they’ve got to go to every component and check it and get rid of all the salt. What you don’t want is a short circuit that causes the system to fail.”…

Finding enough replacement parts will be another challenge that could delay repairs, said Kathy Waters, vice president for member services at the American Public Transportation Association.

“The New York system, although there are some components that have been upgraded over the years, has a lot of antique components where the vendor has been out of business for 50 years,” Waters said in an interview.