Whitemarsh and Plymouth area commuters face disruptions on three separate SEPTA lines starting Saturday, Aug. 1, with shuttle buses replacing trains on the M Line, the Manayunk/Norristown Regional Rail Line, and the West Trenton line.

The new disruptions go beyond the 20-week M Line shutdown we reported July 21. A SEPTA news release published Wednesday confirmed two additional lines will see shuttle bus service tied to bridge construction projects.

Here's what riders need to know:

M Line (Norristown High Speed Line): Shuttle buses replace trains between Norristown Transit Center and Bridgeport Station from Saturday, Aug. 1, through Saturday, Dec. 19. The shuttle zone expands to include Gulph Mills Station from Aug. 22–30 before reverting to Bridgeport Station for the remainder of the construction period. Norristown Transit Center and Gulph Mills Station are the two M Line stops most relevant to local commuters heading toward Center City.

Manayunk/Norristown Regional Rail Line: Shuttle buses replace trains between Norristown-Elm Street station and Norristown Transit Center from Saturday, Aug. 15, through Sunday, Aug. 23. This disruption is also tied to the Bridgeport Viaduct rehabilitation.

West Trenton line: Separately, shuttle buses replace trains between West Trenton and Yardley stations from Saturday, Aug. 1, through Friday, Aug. 14, due to work on the West Trenton Bridge. Those shuttles will depart 14 to 20 minutes earlier than regular train times and could add up to 30 minutes of travel time.

SEPTA said riders on all affected services should expect longer travel times.

The M Line and Manayunk/Norristown disruptions stem from the second phase of the $55 million Bridgeport Viaduct rehabilitation, as previously reported.

SEPTA General Manager Scott A. Sauer described the agency's broader infrastructure challenge in a July 13 Reporter Online interview about regional rail schedule changes: "Our crews are working hard to maintain our aging infrastructure and vehicles until they can be replaced."

Riders can check schedules and real-time updates at septa.org or through the SEPTA App.