Clayton Street — a busy sidestreet between Park and Freeport Streets near Fields Corner— will be closed to traffic this weekend as workers prepare to replace an aging bridge that carries trains on the Dorchester leg of the Red Line.

There will be no interruption to train service this weekend, although service will be halted — and replaced with buses—for three consecutive weekends in July and again in October’s Columbus Day weekend when a new span is scheduled to be installed. Clayton Street will be closed to thru traffic from May 25-27 while abutment tiebacks are installed. The existing steel bridge dates to 1911.