The antiquated Morton Street bridge over the Fairmount Line shuts at 9 a.m. on Friday so the state can replace it with a more modern span.
Officials say the new bridge - pre-built off site - will be moved into place this weekend and that it should be open to traffic by 5 a.m. on Aug. 18.
Due to the work, the 21 and 26 bus routes will be detoured.
