Heavy Fourth of July traffic could cause gridlock on the Northern State, Sagtikos and Sunken Meadow parkways, the state Office of Parks, Recreation and Historic Preservation said Wednesday in a traffic advisory.

Prior years' attendance at Sunken Meadow State Park has caused morning and afternoon gridlock and serious traffic disruptions, the agency said in a news release.

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Motorists are urged to consider other routes for entering Sunken Meadow State Park between 8 a.m. and 6 p.m. July 4.

The agency also said parking is not permitted on the roadways, the center median or grassy shoulder areas, except for short-term emergencies.