Starting Thursday, motorists must use a single lane across the Robert Moses Causeway’s Fire Island Inlet Bridge on weekdays for about three weeks, state transportation officials announced Wednesday.

North- and southbound traffic will alternate, using the only open lane during the hours of 10 a.m. and 3 p.m., state Department of Transportation officials said.

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The plan will allow for safety inspections on a bridge that is more than 50 years old, officials said. They advise motorists to drive carefully through the work zone and obey the 25 mph speed limit.

For real-time travel information, motorists may call 511 or visit 511NY.org.