The Metropolitan Transportation Authority's "Fastrack" program is coming to the 2 and 3 lines in Harlem and the Bronx this week.
Starting Monday night and for the following three nighs, crews will be working on the tracks.
Service on the 2 and 3 will be suspended between 96th Street and 149th Street.
Free shuttle buses provide alternate service.
The work is being done during the overnight hours from 9:30 p.m. until 5 a.m.
It's set to wrap up Friday morning, but it will take place again next week and the week after that.
For more information, go online to mta.info.