An opening of the Cos Cob Bridge near the Cos Cob Station scheduled for 11 a.m. Sunday could cause delays of 20 to 25 minutes.

Those continuing north could also be affected by testing of the Devon Bridge between Stratford and Milford, which could require periodic openings. Each opening would cause a delay of 20 to 25 minutes.

Metro-North said it would keep riders updated throughout the day.