There will be a major service disruption affecting an estimated 40,000 riders on the Long Island Rail Road this weekend while the Ellison Avenue bridge in Westbury is being torn down.

"It's going to have a major impact because it's going to shut down the tracks below us for the entire weekend, around the clock," LIRR President Patrick A. Nowakowski said Thursday as he stood in the concrete dust of the bridge, which as been closed to cars since last month.

"So beginning at midnight on Friday night, we will not run any train service through this area, and that will last until Sunday night at about the same time," he said.

Passengers on the Port Jefferson and Ronkonkoma branches can take shuttle buses between Hicksville and Mineola or find another way to travel, he said.

The railroad suggested that riders on the Ronkonkoma and Port Jefferson branch lines consider using the Babylon, Far Rockaway, Hempstead, Long Beach, Montauk, Port Washington, Oyster Bay or West Hempstead branches during the weekend.

Those branches will experience "minor schedule adjustments," the railroad said.

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The railroad said timetable changes have been posted on its website,

Riders "really need to pay attention to the revised schedules we put out there. We don't want people to be surprised," Nowakowski said.

The railroad said passengers taking a shuttle bus would be delayed 40 to 60 minutes longer than normal on the two branches.

The $17.5 million project includes erecting a new bridge and installing sidewalks, curbs and fencing.

It is scheduled to open in June 2016, but Nowakowski said there will be one additional weekend during the construction period that will require a similar weekend shutdown of service and reduction in service.