Buses will replace trains at the Ronkonkoma and Central Islip stations on the Long Island Rail Road this weekend, the railroad said.

The work on the Ronkonkoma Branch this weekend, from 12:30 a.m. Saturday to 12:30 a.m. Monday, calls for switch installation and related work for the double-track project.

Riders traveling to or from Central Islip or Ronkonkoma should plan for up to an additional 34 minutes of travel time, the railroad said.

In the alternative, they should consider using the Port Jefferson Branch or Montauk Branch, or take advantage of free parking at Brentwood and Deer Park, the railroad said.

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A complete train and bus schedule is at the agency’s website.

The $387-million double-track project is expected to increase capacity along the 18 miles between Farmingdale and Ronkonkoma. Completion is targeted for the end of 2018.