Drivers should expect traffic delays on the South Fork Sunday, Sept. 18, during the 35th annual Mighty Hamptons Triathlon, Southampton Town police said.

The event, which includes a 1.5-kilometer swim, 40-kilometer bike competition and 10-kilometer run, starts at Long Beach in Sag Harbor and runs from 6 a.m. to 11 a.m.

The bike and run portions of the triathlon “will travel on numerous roadways in the Sag Harbor, Noyac, North Sea, Water Mill, Bridgehampton and North Haven areas,” police said Friday in a news release. “A large number of people are expected to attend and traffic delays should be anticipated and expected” particularly on Noyac Road, Majors Path, Head of Pond Road, Scuttlehole Road and Route 114, among others.

Police urge drivers to avoid those roads during the duration of the competition.

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CORRECTION: The date of the triathlon was incorrect in a previous version of this story.