The MBTA says new Silver Line 4 service will get riders from Dudley Station to South Station in 30 minutes, with the first, ceremonial, run scheduled for 1 p.m. on Tuesday.
Buses are scheduled for every 10 minutes during rush hour and 15 minutes the rest of the day. T officials say federal stimulus money was used to get the service started.
The existing Dudley-to-Downtown-Crossing service is now SL5. SL3, which served part of the South Boston waterfront, was discontinued.