Commuters are in for four weeks of reduced and altered rail service from New Jersey Transit and Amtrak. It comes as crews finish up the new Portal Bridge over the Hackensack River.

The nearly $2 billion project is a critical span for commuters on the Northeast Corridor, but riders will need to prepare for the transition from the 111-year-old one.

"We don't wake up in the morning and say, 'How can we disrupt the lives of customers?’ NJ Transit President/CEO Kris Kolluri said. “We wake up in the morning and say, 'How can we improve the lives of customers?' This is an effort to meet that objective."

The “cutover” to the new bridge won't be quick - scheduled for Feb. 15 to March 14. Every NJ Transit rail line except Atlantic City will be impacted. For many, it's a reduction in service.

For Midtown Direct commuters, it's a fundamental change in how they commute to New York. This change affects the Morris & Essex, Gladstone Branch and Montclair-Boonton Lines.

"Five days a week, the trains will go to Hoboken,” Kolluri said. “And there will be access to the 126 bus line and the ferry system, plus PATH, where we'll cross-honor."

There's also going to be a major reduction along the Northeast Corridor - the busiest rail line.

"Currently, we have 332 trains that use the Northeast Corridor between Newark and Penn Station New York,” Kolluri said. “The disruption, for a four-week period, will reduce our traffic by 50%."

Amtrak service is also reduced. Their biggest cut is from 24 daily trains between Philadelphia and New York down to 10.

The work ahead is massive. Catenary poles and foundations will be removed. New railroad will be installed. Crews will work two shifts a day, seven days a week to stay on track.

"We're very confident,” said Amtrak President Roger Harris. “We've been planning this outage for over a year. We've built into the outage a number of recovery days and to anticipate weather and potential technical difficulties."

This outage is to open one track on the new bridge. There will be a second outage in October, after the FIFA World Cup and before Thanksgiving, to complete the second track and fully open the new Portal Bridge.