So instead, Amtrak has been studying ways to fix the interiors of the existing tunnels with minimal disruption to service, a company official said. The plan might cost more than $100 million.

The effects

It was unclear last week exactly how service would be affected, but the repairs would almost certainly mean schedule disruptions for riders in the Northeast — particularly for the 70,000 commuters during rush hour who go to and from Penn Station each weekday.

The tunnels operate at full capacity during peak periods, and they are the sole route for trains moving between Manhattan and New Jersey.

Recent aggravations

Last month, a power failure disabled a train and created chaos for thousands of riders, some of whom were stranded for over four hours on a Monday evening at Penn Station.

Last summer, New Jersey Transit canceled over 60 trains in one week, again leaving thousands of people scrambling to find another way to their destination. The reasons for the cancellations included crew shortages and a lack of available trains.

And then, last fall, Mr. McGeehan perhaps found the worst train in America: North Jersey Coast Line 2606 failed to show up for its morning run nearly 20 times between January and September.