Earlier this month, the term-limited Republican governor said the state would withhold payments to Amtrak until a study verified that the rails were in a state of good repair. The national passenger railroad also warned Amtrak, Long Island Rail Road and New Jersey Transit passengers to expect disruptions. Amtrak says it is accelerating repair work at New York's Penn Station beginning next month, and warns of further delays for already beleaguered commuters. Amtrak announced Thursday it will begin replacing tracks and signals in May and will continue the work through the summer.