Further safety reports into derailments reveal concerns over how soon and how well Network Rail actually repairs known track defects.

BBC: Train crash in Cumbria

But both MTA railroads maintain comprehensive inspection programs on their tracks, according to the MTA. Every two weeks, workers visually inspect "every inch of track" on both Metro-North and Long Island Rail Road systems for defects, an MTA official said.

WSJ: Metro-North Is Set To Restore Full Service Wednesday