The MTA's Fastrack maintenance program is coming to the 4 and 6 lines in Manhattan this week.
Starting Monday night and for the next three nights, crews are working on the tracks.
The 4 and 6 are skipping stops in both directions, between 125th Street and Grand Central.
Special M101 Limited buses will run between those stations along Third Avenue and Lexington Avenue.
The work runs only in the overnight hours from 9:30 p.m. until 5 a.m. and is set to wrap up Friday morning.
For more information, visit mta.info.