Work will begin Feb. 15 to switch NJ Transit and Amtrak train traffic in Secaucus to the new Portal Bridge. That means fewer trains and altered schedules for several lines, including the busiest - the Northeast Corridor.

The new Portal Bridge replaces the old one over Hackensack River that is more than 110 years old. The new bridge, a nearly $2 billion project, is a fixed bridge that won’t have to rotate to let marine traffic pass underneath. Leadership from NJ Transit and Amtrak say this will reduce delays.

But the process of transferring trains to the new bridge, known as a “cutover,” could frustrate commuters for weeks.

From Feb. 15 to March 15, both NJ Transit and Amtrak train service will be reduced. Some New York City-bound commuters will have to make a major transition. The NJ Transit trains along the “Midtown Direct” service that normally pull into Manhattan will instead end in Hoboken on weekdays.

From there, tickets will be cross-honored for the PATH, NYC Ferry or NJ Transit Bus 126. This affects customers on the Morris & Essex, Gladstone Branch and Montclair-Boonton Lines.

Other lines will see reduced service, including the Northeast Corridor, North Jersey Coast Line and Raritan Valley Line. You can see the full schedule here.

NJ Transit and Amtrak say the short-term pain will mean decades of improved service for commuters.

"A temporary disruption, understanding it's a major one will result in a brand-new bridge,” said NJ Transit President/CEO Kris Kolluri. “The first time you're going to have a modern bridge on this section of the Northeast Corridor in over 100 years."

"We're talking here about the transition of the first track on the bridge,” said Amtrak President Roger Harris. “There will be a second outage late this calendar year."

That second outage is tentatively planned in October, to be done after the FIFA World Cup ends and before Thanksgiving.