:M (New York City Subway service)

File:Myrtle Viaduct before reconstruction (41696907722).jpg

Until 1914, the only service on the Myrtle Avenue Line east of Grand Avenue was a local service between Park Row (via the Brooklyn Bridge) and Middle Village (numbered 11 in 1924). The Myrtle Viaduct, a two-track ramp connecting the Myrtle Avenue Line with the BMT Broadway Elevated (now the Jamaica) Line at the Myrtle Avenue station was opened on July 29, 1914, allowing for a second service, the daytime Myrtle Avenue–Chambers Street Line, or Myrtle-Chambers Line, which ran along the Broadway elevated and the Williamsburg Bridge to Chambers Street on the Nassau Street Loop in Lower Manhattan.{{Cite news|date=July 29, 1914|title=New L Loop in Use: Long-Sought Improvement Inaugurated Today|page=1|work=The Brooklyn Daily Eagle|url=https://www.newspapers.com/clip/51867946/the-brooklyn-daily-eagle/|access-date=January 24, 2016}}{{Cite journal|last=Linder|first=Bernard|date=February 1971|title=A History of BRT/BMT Rapid Transit Service 1908–1949|journal=New York Division Bulletin|publisher=Electric Railroaders' Association|pages=6}}

Following the completion of a third track along the Broadway Elevated between Marcy Avenue and Myrtle Avenue on January 17, 1916,{{Cite news|date=January 16, 1916|title=Express Service on the Broadway Line.|work=Brooklyn Standard Journal|url=https://www.newspapers.com/clip/53732529/|url-access=subscription|access-date=June 19, 2020}} these trains began running express on the Broadway Elevated during the evening rush hour in the peak-direction.{{Cite news|date=March 11, 1916|title=Ridgewood Heights Seeks Better Elevated Service: Hear B.R.T. Is Investigating Request For Daily Loop Schedule: Want A Morning Express: Cemetery Assessment Bill Prepared by Assemblyman O'Hare—President Gohlinghorst III|work=The Brooklyn Chat|url=https://www.newspapers.com/clip/53732962/the-chat/|url-access=subscription|access-date=June 19, 2020}} By 1920, trains later began running express in the morning rush hour and on Saturday afternoon in the peak direction.{{Cite journal|last=Linder|first=Bernard|date=April 1971|title=A History of BRT/BMT Rapid Transit Service 1908–1949 – Part Two|journal=New York Division Bulletin|publisher=Electric Railroaders' Association|pages=4}} The number 10 was assigned to the service in 1924."Guide Map to BMT Lines – Rapid Transit Division". Brooklyn—Manhattan Transit. 1924. At the time, service ran on weekdays between 6 a.m. and 8 p.m., on Saturdays from 6 a.m. and 9 p.m., and on Sundays from 12:30 to 11 p.m. In the morning rush hour, trains ran express between Central Avenue and Essex Street, and during the evening rush hour, trains ran express between Bowery and Broadway–Myrtle Avenue.{{Cite journal|last=Linder|first=Bernard|date=June 1966|title=BMT Service History Part I- 1924–1949 Subway & El|journal=New York Division Bulletin|publisher=Electric Railroaders' Association}}

Sunday service was removed in June 1933. All Saturday trains began running local on June 28, 1952. On February 10, 1958, the four rush hour Brighton-Nassau special trains began stopping at Neck Road and Avenue U. In addition, the evening rush hour trains began stopping at DeKalb Avenue, as had been done by morning rush hour trains.{{Cite web |date=1958 |title=Additional Service for Neck Road and Avenue "U" Passengers |url=https://www.flickr.com/photos/unionturnpike/52580663506/in/datetaken-public/ |access-date=December 22, 2022 |website=Flickr |publisher=New York City Transit Authority}} On June 28, 1958, Saturday service was discontinued. On May 26, 1959, midday service was eliminated, making the Myrtle-Chambers Line rush-hours only. Service had previously operated on weekdays from 6 a.m. to 8 p.m.{{Cite news|last=Kline|first=Polly|date=May 21, 1959|title='Bright New Day' For BMT Riders Has Grey Shades|pages=502|url-access=subscription|work=New York Daily News|url=https://www.newspapers.com/clip/51866422/bright-new-day-for-bmt-riders-has/|access-date=May 22, 2020}} Beginning on February 23, 1960, express trains began stopping at Marcy Avenue, which was originally a local stop.{{Cite journal|last=Linder|first=Bernard|date=August 1966|title=History of BMT Subway-L Services Part II-1949 To the Present|journal=New York Division Bulletin|publisher=Electric Railroaders' Association}}

{{Plain image with caption|M Train (1967-1979).svg|1967–1979 bullet|75px}}

In 1961, with the arrival of new R27s which featured rollsigns with new lettered designations for the BMT's numbered services, the 10 was renamed the M.{{Cite book|last=Sansone|first=Gene|url=https://books.google.com/books?id=6WFHNSXBpocC|title=New York Subways: An Illustrated History of New York City's Transit Cars|date=November 29, 2004|publisher=JHU Press|isbn=978-0-8018-7922-7|pages=216|language=en}}{{Cite journal|date=April 1960|title=Roll Signs List For BMT-IND R-27's|url=https://erausa.org/pdf/bulletin/1960/1960-04-bulletin.pdf|journal=New York Division Bulletin|publisher=Electric Railroaders' Association|volume=3|issue=4|pages=1–3}} Since these cars were not assigned to the route,{{Cite journal|last=Oszustowicz|first=Eric R.|date=August 2005|title=New York City Subway Car Rosters and Assignments, 1961–1971|url=https://erausa.org/pdf/bulletin/2005/2005-08-bulletin.pdf|journal=The Bulletin|publisher=Electric Railroader's Association|volume=48|issue=8|pages=5–9}} it remained signed as 10. However, the rush hour Nassau Street specials on the BMT Brighton Line and BMT Fourth Avenue Line were signed using the M designation.{{Cite book|last1=Cunningham|first1=Joseph|url=https://books.google.com/books?id=Fg4KAQAAMAAJ&q=1961+M|title=A History of the New York City Subway System|last2=DeHart|first2=Leonard O.|date=1993|publisher=J. Schmidt, R. Giglio, and K. Lang|language=en}}{{Rp|86}} The line was officially designated "M" after the Chrystie Street changeover on November 27, 1967.{{Cite web|date=November 1967|title=Rapid Transit Guide|url=https://www.flickr.com/photos/127872292@N06/24936413491/in/album-72157652636594213/|access-date=June 19, 2020|website=Flickr|publisher=New York City Transit Authority}}

The second half of the Chrystie Street Connection opened on July 1, 1968, and the {{NYCS|JJ}}, which had run along Nassau Street to Broad Street, was relocated through the new connection to the IND Sixth Avenue Line (and renamed the KK). To augment {{NYCS|QJ}} service to Broad Street, the M was extended two stations, from Chambers Street to Broad Street.{{cite news|url=https://timesmachine.nytimes.com/timesmachine/1968/07/01/76872122.pdf|title=Skip-Stop Subway Begins Run Today; KK Line Links 3 Boroughs --Other Routes Changed|url-access=subscription|work=The New York Times|date=July 1, 1968|issn=0362-4331}}

On October 4, 1969, the Myrtle Avenue Elevated was discontinued south of Myrtle Avenue to Jay Street. To make up for the loss of MJ service, M service was expanded to run during middays, operating weekdays between 6 a.m. and 7 p.m., and a new SS shuttle began running between Myrtle Avenue and Metropolitan Avenue at other times.{{Cite web|title=Service Changes For Myrtle Avenue "El" Riders|url=https://www.flickr.com/photos/127872292@N06/24823877747/in/album-72157652636620504/|date=October 1969|website=Flickr|publisher=New York City Transit Authority|access-date=May 22, 2020}} In August 1972, the off-hour SS shuttle was renamed as part of the M.{{Cite book|last1=Lloyd|first1=Peter B.|url=https://books.google.com/books?id=lnX1MgEACAAJ|title=Vignelli Transit Maps|last2=Ovenden|first2=Mark|date=2012|publisher=RIT Cary Graphic Arts Press|isbn=978-1-933360-62-1|language=en}}{{Rp|62}}

Effective January 2, 1973, the daytime QJ was truncated to Broad Street as the {{NYCS|J}}, and the M was extended beyond Broad Street during the day along the {{NYCS|QJ}}'s former route to Coney Island–Stillwell Avenue, via the Montague Street Tunnel and Brighton Line local tracks. With the extension of the M onto the Brighton Line, there were also changes to D service. Northbound weekday M train service originating at Kings Highway would begin at 5:46 a.m., while northbound service from Coney Island would begin at 6:34 a.m. From 5:40 to 6:34 a.m. northbound D trains would run local from Brighton Beach to Kings Highway, and then run express to Prospect Park. Late morning and early afternoon D trains would from then on run express from Brighton Beach to Kings Highway. The span of D express service to Brighton Beach was extended by 45 minutes to 9:05 p.m. from Prospect Park, and the span of M service from Broad Street to Coney Island was extended by 45 minutes from the previous span of QJ service to cover local stops.{{Cite web |date=1972 |title=To Serve You Better... On The Brighton Line in Brooklyn |url=https://www.flickr.com/photos/unionturnpike/51339412780/in/datetaken/ |access-date=July 27, 2021 |website=Flickr |publisher=New York City Transit Authority}}{{Cite web|title=To Serve You Better...|url=https://www.flickr.com/photos/127872292@N06/27244132688/in/album-72157652636620504/|date=1972|website=Flickr|publisher=New York City Transit Authority|access-date=May 22, 2020}} Two M trains began service at Brighton Beach in the morning rush hour, and in the early morning, three M trains entered service at Brighton Beach, and six entered service at Kings Highway. In addition, the final nine southbound M trains of the evening terminated at Brighton Beach. On May 13, 1974, three northbound early morning trains that were placed into service at Brighton Beach were replaced with two trains entering service at Kings Highway and one entering service at Brighton Beach.{{Cite journal |last=Linder |first=Bernard |date=April 2003 |title=Brighton Line Schedule Changes |url=https://erausa.org/pdf/bulletin/2000s/2003/2003-04-bulletin.pdf |journal=New York Division Bulletin |publisher=Electric Railroaders' Association |volume=46 |issue=4 |pages=2–3}}

The local K (renamed from KK in 1973) was eliminated on August 27, 1976,{{Cite news|date=August 31, 1976|title=Transit Agency Drops 215 Runs; Resulting Schedule Shifts Bewilder Passengers|url-access=subscription|work=The New York Times|url=https://timesmachine.nytimes.com/timesmachine/1976/08/31/75549301.pdf|access-date=October 23, 2016|issn=0362-4331}} and M express service between Myrtle Avenue and Marcy Avenue ended.{{Cite web|url=https://www.flickr.com/photos/127872292@N06/30393951262/|title=Service Adjustment on BMT and IND Lines Effective 1 A.M. Monday, Aug. 30|date=August 1976|website=Flickr|publisher=New York City Transit Authority|access-date=October 23, 2016}}

On December 3, 1979, four northbound weekday morning rush hour trains that had been put into service at Kings Highway began service at Brighton Beach.

File:Williamsburg Bridge train 2 vc.jpg crossing the Williamsburg Bridge in 1995|alt=|right]]

A six-month reconstruction project on the Brighton Line began on April 26, 1986, and to reduce congestion and delays, weekday daytime M service was shifted to the Fourth Avenue Line's express tracks south of DeKalb Avenue and the BMT West End Line. Service began terminating at Ninth Avenue during middays, and at Bay Parkway during rush hours.{{Cite news|url=https://www.newspapers.com/clip/32873701/daily_news/|title=A Change Urged to Lessen Delays in M-Line Rehab|last=Rabin|first=Bernard|date=April 16, 1986|url-access=subscription|work=New York Daily News|access-date=June 14, 2019}} This service duplicated a pattern that had last been operated as the {{NYCS|TT}} until late 1967.{{Cite news|title=Brighton Line Riders Your Guide To Service Changes On The B Q M During Rehabilitation Work April 26 Through October 26, 1986|date=April 1986|publisher=New York City Transit Authority}} Manhattan-bound M trains operated from Bay Parkway between about 7:00 and 8:20 a.m., operating every 12 to 15 minutes. Bay Parkway-bound M trains left Chambers Street between 4:20 and 5:30 p.m.{{Cite web|title=West End, 4 Ave, Sea Beach Line Riders: Your Guide To Service Changes On The B M N R During Rehabilitation Work April 26 Through October 26, 1986|url=https://www.flickr.com/photos/127872292@N06/27065548073/in/album-72157652637328843/|date=April 1986|website=Flickr|publisher=New York City Transit Authority|access-date=May 22, 2020}} In 1991, M trains began running with fewer cars at all times except weekdays from 6 a.m. to 8 p.m. in order to increase passenger security during overnight hours.*{{Cite web|title=Riders' Guide To Reduced Train Lengths|url=https://www.flickr.com/photos/127872292@N06/28787722283/in/album-72157702397602704/|date=1991|website=Flickr|publisher=New York City Transit Authority|access-date=May 19, 2020}}

• {{Cite web|title=Riders' Guide To Reduced Train Lengths|url=https://www.flickr.com/photos/127872292@N06/28787722863/in/album-72157702397602704/|date=1991|website=Flickr|publisher=New York City Transit Authority|access-date=May 19, 2020}}

M service along Fourth Avenue, operating between 6:30 a.m. and 8:00 p.m., was switched to the local tracks on May 31, 1994, switching with the {{NYCS|N}}, which had run local since the M was moved in 1987.{{Cite news|title=A Customer Timetable for New York City Subway Services on the M Train|date=May 29, 1994|publisher=New York City Transit}}{{Cite web|url=https://www.flickr.com/photos/127872292@N06/16543351666/in/album-72157652636594213/|title=May 1994 Subway Map|date=May 1994|work=Flickr|publisher=New York City Transit|language=en-us|access-date=October 7, 2018}} The change was implemented on a six-month trial, and was made permanent afterwards. This change was made as part of New York City Transit's Fare Deal, which sought to increase transit ridership by improving service. The change was proposed in November 1993, and public hearings on the change were held.{{Cite news|url=https://www.nytimes.com/1993/11/14/nyregion/neighborhood-report-sunset-park-subway-express-battle.html|title=Neighborhood Report: Sunset Park; Subway Express Battle|last=Holloway|first=Lynette|date=November 14, 1993|url-access=subscription|work=The New York Times|access-date=June 14, 2019|language=en-US|issn=0362-4331}} The change reduced travel times by {{frac|4|1|2}} minutes for 26,000 people, a majority of the riders on the corridor. As a result of the change, some riders shifted from using stations on the BMT West End Line to the BMT Sea Beach Line, and from Fourth Avenue local stops to Fourth Avenue express stops.*{{Cite book|url=https://www.flickr.com/photos/127872292@N06/46561357024/in/album-72157707344749114/|title=Fare Deal 1994 Ridership Growth Service Initiatives First Year Preliminary Report March 1995|date=March 1995|publisher=New York City Transit|pages=7}}

• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/32342746377/in/album-72157707344749114/|title=Fare Deal 1994 Ridership Growth Service Initiatives First Year Preliminary Report March 1995|date=March 1995|publisher=New York City Transit|pages=13}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/46369973085/in/album-72157707344749114/|title=Fare Deal 1994 Ridership Growth Service Initiatives First Year Preliminary Report March 1995|date=March 1995|publisher=New York City Transit|pages=A-20}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/46369972845/in/album-72157707344749114/|title=Fare Deal 1994 Ridership Growth Service Initiatives First Year Preliminary Report March 1995|date=March 1995|publisher=New York City Transit|pages=A-21}} Market research found that 44% of M riders felt that crowding decreased, that 35% of M and 30% of N riders used their service more frequently, that 58% of riders thought the change was a good idea, and that only riders at the 45th Street and 53rd Street stations, which received less frequent service, viewed the changes negatively. This change increased operating costs by $245,000.*{{Cite book|url=https://www.flickr.com/photos/127872292@N06/48013660223/in/album-72157708954782547/|title=Fare Deal 1994 Ridership Growth Service Initiatives First Year Final Report September 1995|date=March 1995|publisher=New York City Transit|pages=I.16}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/48013731462/in/album-72157708954782547/|title=Fare Deal 1994 Ridership Growth Service Initiatives First Year Final Report September 1995|date=March 1995|publisher=New York City Transit|pages=I.21}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/48013653293/in/album-72157708954782547/|title=Fare Deal 1994 Ridership Growth Service Initiatives First Year Final Report September 1995|date=March 1995|publisher=New York City Transit|pages=I.23}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/48013613251/in/album-72157708954782547/|title=Fare Deal 1994 Ridership Growth Service Initiatives First Year Final Report September 1995|date=March 1995|publisher=New York City Transit|pages=I.62}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/48013624113/in/album-72157708954782547/|title=Fare Deal 1994 Ridership Growth Service Initiatives First Year Final Report September 1995|date=March 1995|publisher=New York City Transit|pages=I.63}}

The midday M (between 9:30 a.m. and 3:30 p.m.) was temporarily truncated to Chambers Street on April 30, 1995, from Ninth Avenue in Brooklyn due to the closure of the Manhattan Bridge during weekday middays for structural repairs.{{Cite news|title=A Customer Timetable for New York City Subway Services on the M Train; Includes Manhattan Bridge Service Information|date=April 30, 1995|publisher=New York City Transit}}*{{Cite web|url=https://www.flickr.com/photos/127872292@N06/16544869056/in/album-72157654548396510/|title=A customer timetable for New York City subway service on the M Train Effective April 30, 1995 Includes Manhattan Bridge Service Information|date=April 30, 1995|website=Flickr|publisher=New York City Transit|access-date=June 14, 2019}}

• {{Cite web|url=https://www.flickr.com/photos/127872292@N06/16384942837/in/album-72157654548396510/|title=A customer timetable for New York City subway service on the M Train Effective April 30, 1995 Includes Manhattan Bridge Service Information|date=April 30, 1995|website=Flickr|publisher=New York City Transit|access-date=June 14, 2019}}
• {{Cite web|url=https://www.flickr.com/photos/127872292@N06/16383415410/in/album-72157654548396510/|title=A customer timetable for New York City subway service on the M Train Effective April 30, 1995 Includes Manhattan Bridge Service Information|date=April 30, 1995|website=Flickr|publisher=New York City Transit|access-date=June 14, 2019}}*{{Cite web|url=https://www.flickr.com/photos/127872292@N06/46813083651/in/album-72157652637328843/|title=Attention Midday and Weekend B M N R Customers Manhattan Bridge Service Change Information|date=1995|website=Flickr|publisher=New York City Transit|access-date=June 14, 2019}}
• {{Cite web|url=https://www.flickr.com/photos/127872292@N06/32937258268/in/album-72157652637328843/|title=Attention Midday and Weekend B M N R Customers Manhattan Bridge Service Change Information|date=1995|website=Flickr|publisher=New York City Transit|access-date=June 14, 2019}}
• {{Cite web|url=https://www.flickr.com/photos/127872292@N06/32937258028/in/album-72157652637328843/|title=Attention Midday and Weekend B M N R Customers Manhattan Bridge Service Change Information|date=1995|website=Flickr|publisher=New York City Transit|access-date=June 14, 2019}} The change was made to provide capacity in the Montague Street Tunnel for the Q, which was rerouted from the Manhattan Bridge. To replace M local service in Brooklyn, midday N trains began making local stops in Brooklyn. In addition, the span of M service to Brooklyn was reduced by fifteen minutes in the early morning and in the late evening by 25 minutes.*{{Cite book|url=https://www.flickr.com/photos/127872292@N06/45778466775/in/album-72157708861628486/|title=New York City Transit Committee Meeting March 1995|date=March 1995|publisher=New York City Transit|pages=D.62}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/45778465925/in/album-72157708861628486/|title=New York City Transit Committee Meeting March 1995|date=March 1995|publisher=New York City Transit|pages=D.63}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/45778465095/in/album-72157708861628486/|title=New York City Transit Committee Meeting March 1995|date=March 1995|publisher=New York City Transit|pages=D.64}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/45778464335/in/album-72157708861628486/|title=New York City Transit Committee Meeting March 1995|date=March 1995|publisher=New York City Transit|pages=D.65}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/45778463275/in/album-72157708861628486/|title=New York City Transit Committee Meeting March 1995|date=March 1995|publisher=New York City Transit|pages=D.66}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/31752260887/in/album-72157708861628486/|title=New York City Transit Committee Meeting March 1995|date=March 1995|publisher=New York City Transit|pages=D.67}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/31752260887/in/album-72157708861628486/|title=New York City Transit Committee Meeting March 1995|date=March 1995|publisher=New York City Transit|pages=D.68}}

The elimination of midday service to Brooklyn was made permanent on November 12, 1995, after the six-month repair project was completed,{{Cite web|url=https://www.flickr.com/photos/127872292@N06/33801080545/in/album-72157654548396510/|title=A Customer Timetable for New York City Subway Services on the M Train|date=November 12, 1995|website=Flickr|publisher=New York City Transit}} as part of a series of service cuts made by New York City Transit to make up a shortfall in its budget. It had been expecting a $160 million surplus in 1995, but due to reductions in state and federal contributions, it was left with a deficit which could reach $172 million. The elimination of midday M service to Brooklyn was part of a larger plan to reduce spending in order to avert a fare increase, which Governor George Pataki and Mayor Rudy Giuliani had pressured the MTA to avoid. Only 4,200 riders used M service to Brooklyn during middays, with fewer than 20 passengers per car, or 80 passengers per train (the M used four-car trains during middays). Because of the low cost effectiveness of operating service to Brooklyn and because of the existence of alternate service on the N and R, it was decided to cut the service. This service cut saved $664,000 annually. Three alternative operating plans were considered: maintaining existing midday service, terminating midday service at Broad Street, and operating service as a shuttle like weekend and late night service. It was decided not to terminate service at Broad Street because it negated a large portion of the crew savings due to the need for personnel to relay trains at the Broad Street terminal, longer running times, and because it had the potential to delay J service, which already terminated there. The shuttle option was dismissed because it would inconvenience a far larger number of M riders.*{{Cite book|url=https://www.flickr.com/photos/127872292@N06/48006739687/in/album-72157708930708123/|title=NYC Transit Committee Agenda July 1995|date=July 21, 1994|publisher=New York City Transit|pages=D.294}}

• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/48006650151/in/album-72157708930708123/|title=NYC Transit Committee Agenda July 1995|date=July 21, 1994|publisher=New York City Transit|pages=D.295}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/48006738382/in/album-72157708930708123/|title=NYC Transit Committee Agenda July 1995|date=July 21, 1994|publisher=New York City Transit|pages=D.296}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/48006648801/in/album-72157708930708123/|title=NYC Transit Committee Agenda July 1995|date=July 21, 1994|publisher=New York City Transit|pages=D.297}}
• {{Cite book|url=https://www.flickr.com/photos/127872292@N06/48006655998/in/album-72157708930708123/|title=NYC Transit Committee Agenda July 1995|date=July 21, 1994|publisher=New York City Transit|pages=D.299}} Truncation of midday M service was proposed as early as January 1991 for an October implementation of that year, subject to approval from the MTA board.{{cite web |title=1991 Service Capacity Plan |url=http://www.laguardiawagnerarchive.lagcc.cuny.edu/pages/FileBrowser.aspx?LinkToFile=FILES_DOC/QUEENS_FILES/03.012.0231.030147.2.PDF#undefined |publisher=New York City Transit Authority |access-date=September 18, 2024 |page=201 |date=January 4, 1991}}

{{Plain image with caption|NYCS-bull-trans-Md brown.svg|Brown M diamond bullet 1986–2005|75px}}

File:R160A M train.jpg M shuttle train at Myrtle Avenue-Broadway]]

From May 1 to September 1, 1999, the Williamsburg Bridge subway tracks were closed for reconstruction, splitting M service in two sections. One service ran at all times between Middle Village–Metropolitan Avenue and Marcy Avenue. The other ran rush hours only between Bay Parkway and Chambers Street. A shuttle provided service on the BMT Nassau Street Line. Fares on the B39 bus crossing the Williamsburg Bridge were eliminated and free subway-bus transfers were given at Marcy Avenue and at Delancey Street.{{cite web|url=http://www.subwaynut.com/brochures/williamsburgbpg.htm|title=No Trains Over The Williamsburg Bridge|date=1999|publisher=New York City Transit|website=subwaynut.com|access-date=November 9, 2014|archive-date=March 3, 2016|archive-url=https://web.archive.org/web/20160303225642/http://www.subwaynut.com/brochures/williamsburgbpg.htm|url-status=dead}} The closure was anticipated to last until October 1999, but subway service was restored one month ahead of schedule.{{Cite web|url=http://www.nyc.gov/html/dot/html/infrastructure/williamsburg-bridge.shtml|title=Williamsburg Bridge|website=nyc.gov|publisher=New York City Department of Transportation|access-date=June 6, 2016|archive-url=https://web.archive.org/web/20200221165833/http://www.nyc.gov/html/dot/html/infrastructure/williamsburg-bridge.shtml|archive-date=February 21, 2020|url-status=live}} The project cost $130 million, including replacing the tracks' support structure, signal systems and other equipment.{{Cite news|url=http://www.nydailynews.com/archives/news/joy-train-riders-flying-high-fixed-up-w-burg-span-article-1.843831|title=It's J – As In Joy – Train Riders Flying High On Fixed-Up W'Burg Span|last=Donohue|first=Pete|date=September 2, 1999|work=New York Daily News|access-date=June 6, 2016}}

From July 23, 2001, to February 22, 2004, the closure of the north tracks on the Manhattan Bridge resulted in a midday extension back to Ninth Avenue, as well as an extension of the times that the rush hour service was provided to 10 p.m. This change preserved service between the West End Line and Chinatown for passengers that would have taken the {{NYCS|B}} to Grand Street.{{cite journal |title=The Repeal of Chrystie Street |journal=The Bulletin |url=https://erausa.org/pdf/bulletin/2000s/2001/2001-09-bulletin.pdf |date=September 2001 |publisher=New York Division, Electric Railroaders' Association |volume=44 |number=9 |pages=2-3 |access-date=March 31, 2025}} When full Manhattan Bridge service was restored, midday M service was cut back to Chambers Street and replaced in south Brooklyn by the {{NYCS|D}}.{{cite web|url=http://mta.info/nyct/service/pdf/tmcur.pdf |title=M Train Timetable Effective April 2003 |access-date=June 6, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20030607111302/http://mta.info/nyct/service/pdf/tmcur.pdf |archive-date=June 7, 2003|publisher=Metropolitan Transportation Authority|website=mta.info }}{{Cite web|url=http://www.mta.info/nyct/man_bridge/manhbr_map.pdf |title=B D M N Q R W Weekday Service Manhattan Bridge Map |date=February 2004 |website=mta.info |publisher=Metropolitan Transportation Authority |access-date=September 18, 2016 |url-status=dead|archive-url=https://web.archive.org/web/20040205124437/http://www.mta.info/nyct/man_bridge/manhbr_map.pdf |archive-date=February 5, 2004 }}{{Cite web|url=http://www.mta.info/nyct/man_bridge/bridge_lines.htm#w |title=MTA NYC Transit Manhattan Bridge Information |date=February 5, 2004 |access-date=September 18, 2016 |url-status=dead |archive-url=https://web.archive.org/web/20040205055553/http://www.mta.info/nyct/man_bridge/bridge_lines.htm#w |archive-date=February 5, 2004|website=mta.info|publisher=Metropolitan Transportation Authority }} Neighborhood leaders in Chinatown were angered by the decision to terminate midday at Ninth Avenue, instead of running it to Bay Parkway. A spokesman for New York City Transit stated that it was easier to terminate trains at Ninth Avenue and that a signal upgrade project was going on further down the line.{{Cite news|url=https://www.nytimes.com/2001/08/05/nyregion/neighborhood-report-chinatown-deal-subways-stops-short-destinations-riders-say.html|title=Neighborhood Report: Chinatown; Deal on Subways Stops Short of Destinations, Riders Say|last=Lee|first=Denny|date=August 5, 2001|url-access=subscription|work=The New York Times|access-date=June 14, 2019|language=en-US|issn=0362-4331}} In addition, the temporary midday service to Brooklyn was lightly used, with an average of 50 to 60 riders per train during middays going to Brooklyn, and fewer than 50 riders per train during evenings going to Brooklyn.{{Cite book|url=https://books.google.com/books?id=5KUCDw_OfgsC|title=MTA Board Action Items|date=September 2003|publisher=Metropolitan Transportation Authority|language=en}}{{Rp|49}}

After the September 11, 2001 attacks, M service initially operated as a shuttle between Metropolitan Avenue and Myrtle Avenue–Broadway.{{cite news|url=https://www.newspapers.com/clip/53731081/subway-service-ventures-farther-into/|first=Michael R.|last=Blood|title=Subway Service Ventures Farther into Downtown|work=New York Daily News|url-access=subscription|date=September 16, 2001|access-date=June 19, 2020}} On September 17, M service was rerouted via the Sea Beach Line and originated and terminated at Stillwell Avenue to replace the {{NYCS|N}}, which got suspended; service via the West End Line continued to be provided by {{NYCS|W}} trains. M trains made all stops along the reroute.{{cite news|first=Pete|last=Donohue|date=September 17, 2001|url=https://www.newspapers.com/clip/53730765/subways-radically-changed/|work=New York Daily News|url-access=subscription|title=Subways 'Radically Changed'|access-date=June 19, 2020}}{{cite journal |title=World Trade Center Destroyed |journal=The Bulletin |url=https://erausa.org/pdf/bulletin/2000s/2001/2001-10-bulletin.pdf |date=October 2001 |publisher=Electric Railroaders' Association |volume=44 |number=10 |pages=2-3 |access-date=March 27, 2025}}{{cite journal |title=New IRT and BMT Schedules |journal=The Bulletin |url=https://erausa.org/pdf/bulletin/2000s/2001/2001-12-bulletin.pdf |date=December 2001 |publisher=Electric Railroaders' Association |volume=44 |number=12 |pages=15 |access-date=March 27, 2025}} Normal M service was restored on October 28.{{cite journal |title=New IRT and BMT Schedules |journal=The Bulletin |url=https://erausa.org/pdf/bulletin/2000s/2001/2001-12-bulletin.pdf |date=December 2001 |publisher=Electric Railroaders' Association |volume=44 |number=12 |pages=16 |access-date=March 27, 2025}}

In December 2007, the MTA announced that it planned to set aside $27 million in 2008 and $60 million annually afterwards for service enhancements to help riders deal with increased fares. Extended weekday evening M service to Broad Street and weekend service to Chambers Street were part of the plan.{{Cite web|url=http://web.mta.info/mta/budget/feb2008/0208_5.pdf|title=MTA 2008 Adopted Budget February Financial Plan 2008–2011 Appendix|date=February 2018|website=mta.info|publisher=Metropolitan Transportation Authority|page=11|access-date=October 15, 2018|archive-url=https://web.archive.org/web/20150131162934/http://web.mta.info/mta/budget/feb2008/0208_5.pdf|archive-date=January 31, 2015|url-status=live}} However, on March 24, 2008, it was announced that because the agency received substantially less revenue from taxes on real estate transactions, the enhancements were reduced to $4.5 million in 2008 and $8.9 million annually afterwards.{{Cite news|url=https://www.nytimes.com/2008/06/19/nyregion/19service.html|title=Subway Service Increase to Be Less Than Hoped|last=Neuman|first=William|date=June 19, 2008|url-access=subscription|work=The New York Times|access-date=October 15, 2018|language=en|issn=0362-4331}}{{Cite news|url=https://cityroom.blogs.nytimes.com/2008/03/24/mta-postpones-subway-and-bus-service-upgrades/|title=M.T.A. Postpones Subway and Bus Service Upgrades|last=Neuman|first=William|date=March 24, 2008|url-access=subscription|work=The New York Times|access-date=October 15, 2018|language=en|issn=0362-4331}} The plan to extend weekend service to Chambers Street was dropped. After several months' delay, weekday evening trains were extended to Broad Street on July 27, 2008.{{cite web|url=http://www.mta.info/nyct/service/pdf/tmcur.pdf|title=M Train Timetable Effective December 2008|website=mta.info|publisher=Metropolitan Transportation Authority|date=December 21, 2008|archive-url=https://web.archive.org/web/20081221064845/http://www.mta.info/nyct/service/pdf/tmcur.pdf|archive-date=December 21, 2008}}{{Cite web|url=http://www.mta.info/press-release/nyc-transit/service-adjustments-bmw-lines|title=Service Adjustments on BMW Lines|date=July 24, 2008|website=mta.info|publisher=Metropolitan Transportation Authority|language=en|access-date=October 15, 2018|archive-url=https://web.archive.org/web/20151222200140/http://www.mta.info/press-release/nyc-transit/service-adjustments-bmw-lines|archive-date=December 22, 2015|url-status=live}}{{Plain image with caption|NYCS-bull-trans-M brown.svg|1979–2010 bullet, when the M served the BMT Nassau Street Line in Lower Manhattan, and 2017–2018 bullet for the shuttle service, as the orange M is not present on older rolling stock.|75px}}

File:Marty Markowitz, Daniel Squadron, Michael Burke, Paul Nelson.jpg

On November 20, 2008, in light of severe budget woes, the MTA announced a slew of potential service cuts; among them was the potential elimination of rush-hour M service which had extended beyond Chambers Street on the Nassau Street Line in Lower Manhattan to Bay Parkway on the West End Line in Brooklyn.{{Cite news|last1=Neuman|first1=William|last2=Chan|first2=Sewell|date=November 20, 2008|title=M.T.A. Plans Steep Service Cuts and Fare Increase|url-access=subscription|work=The New York Times|url=https://cityroom.blogs.nytimes.com/2008/11/20/mta-plans-steep-service-cuts-and-fare-increase/|access-date=June 4, 2020|issn=0362-4331}} In May 2009, after the New York State Legislature passed legislation to offer financial support to the MTA, the service cut was taken off the table.{{Cite news|last1=Neuman|first1=William|last2=Confessore|first2=Nicholas|date=May 4, 2009|title=Bailout Plan for M.T.A. Gains Two Essential Votes|language=en-US|url-access=subscription|work=The New York Times|url=https://www.nytimes.com/2009/05/05/nyregion/05mta.html|access-date=June 4, 2020|issn=0362-4331}} However, in late 2009, the MTA once again discovered that it was confronting another financial crisis; most of the same service cuts threatened just months earlier were revisited. One proposal included completely phasing out M service and using the {{NYCS|V}} as its replacement. Under this proposal, the V would no longer serve its southern terminus at Second Avenue. Instead, after leaving Broadway–Lafayette Street, it would run along the Chrystie Street–Williamsburg Bridge connection, unused since the elimination of the K in 1976, and stop at the upper (BMT) level of Essex Street in Manhattan before serving all M stations to Metropolitan Avenue in Queens.{{Cite book|last=Sparberg|first=Andrew J.|url=https://books.google.com/books?id=T1GoDwAAQBAJ&q=chrystie+street+connection+m+train+1976+2010&pg=PA158|title=From a Nickel to a Token: The Journey from Board of Transportation to MTA|date=November 3, 2014|publisher=Fordham University Press|isbn=978-0-8232-6192-5|pages=58|language=en}}

The MTA determined that this move, while still a service cut, would actually benefit M riders in northern Brooklyn; approximately 17,000 weekday riders used that route to reach its stations in Lower Manhattan, whereas 22,000 transferred to other routes to reach destinations in Midtown Manhattan. However, only about 10,000 riders in Southern Brooklyn used the M to access the Nassau Street Line. This merger opened up new travel options for northern Brooklyn and Queens in that it allowed direct and more convenient access to areas that were not previously served by those routes such as Midtown Manhattan, as before the service changes, M train passengers had to transfer at least once if heading to Midtown.{{cite web|url=http://www.mta.info/nyct/service/ServiceReduction/part1.htm |title=2010 NYC Transit Service Reductions |date=January 27, 2010 |website=mta.info|publisher=Metropolitan Transportation Authority |url-status=dead |archive-url=https://web.archive.org/web/20140313123213/http://www.mta.info/nyct/service/ServiceReduction/part1.htm |archive-date=March 13, 2014 }}

On March 19, 2010, it was reported that the plan had been changed and that the new combined service would instead carry the M train designation, recolored orange to designate the IND Sixth Avenue Line as its Manhattan trunk line, while discontinuing the V train. Many MTA board members opposed the elimination of the M designation, saying that riders would be more comfortable with that rather than a V designation, and because the M had been around longer than the V.{{cite news |title=Under a New Subway Plan, The V Stands for Vanished |first=Michael M. |last=Grynbaum |url=https://www.nytimes.com/2010/03/20/nyregion/20train.html |url-access=subscription|work=The New York Times |date=March 19, 2010 |access-date=March 20, 2010|issn=0362-4331}}{{cite web|url=http://web.mta.info/news/pdf/NYCT_Summary_of_Revisions.pdf|publisher=Metropolitan Transportation Authority|website=mta.info|date=March 19, 2010|title=Re:Modification to 2010 NYC Transit Service Reductions|access-date=June 19, 2020|archive-date=June 6, 2014|archive-url=https://web.archive.org/web/20140606235349/http://web.mta.info/news/pdf/NYCT_Summary_of_Revisions.pdf|url-status=live}} The last M trains to Bay Parkway ran on June 25, 2010,{{Cite web |date=June 24, 2010 |title=Major Subway Changes Set for Monday |url=http://www.mta.info/press-release/nyc-transit/major-subway-changes-set-monday |url-status=live |archive-url=https://web.archive.org/web/20151228091809/http://www.mta.info/press-release/nyc-transit/major-subway-changes-set-monday |archive-date=December 28, 2015 |access-date=October 20, 2016 |website=mta.info |publisher=Metropolitan Transportation Authority}} and M service via the Chrystie Street Connection began the following Monday, June 28, 2010.{{Cite web|url=http://web.mta.info/mta/news/books/docs/NYCT_2010_Service_Reduction_Evaluation.pdf|title=Evaluation of 2010 Service Reductions|date=September 23, 2011|website=mta.info|publisher=Metropolitan Transportation Authority|access-date=October 20, 2016|archive-url=https://web.archive.org/web/20151208101254/http://web.mta.info/mta/news/books/docs/NYCT_2010_Service_Reduction_Evaluation.pdf|archive-date=December 8, 2015|url-status=live}}{{Cite news |last=Barron |first=James |date=June 28, 2010 |title=City Commuters Press On Despite Transit Cuts |language=en-US |work=The New York Times |url=https://www.nytimes.com/2010/06/29/nyregion/29transit.html |access-date=June 1, 2023 |issn=0362-4331}}

On June 8, 2014, weekend daytime M service was extended to Essex Street as part of an $18 million funding project to improve subway service, as well as to offer a direct connection to the F train on Saturdays and Sundays. Late night service continues to terminate at Myrtle Avenue.{{Cite web|url=http://web.mta.info/nyct/service/2014_2017MTAFinancialPlan.htm|archive-url=https://web.archive.org/web/20130725182925/http://web.mta.info/nyct/service/2014_2017MTAFinancialPlan.htm|url-status=dead|title=2014 – 2017 MTA Financial Plan|website=mta.info|publisher=Metropolitan Transportation Authority|archive-date=July 25, 2013}}{{cite web|url=http://web.mta.info/nyct/service/M_weekends.htm |title=M Weekends Beginning Sunday, June 8, 2014 Go More Places...|access-date=June 7, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140612005620/http://web.mta.info/nyct/service/M_weekends.htm |archive-date=June 12, 2014|publisher=Metropolitan Transportation Authority|website=mta.info }}

During the morning rush hour, the M is at 90 percent of the New York City Subway's capacity guidelines. Ridership on the M has been growing very rapidly since the 2010 service change, and this trend is expected to continue. In June 2016, the frequencies of service on the M route during peak hours were increased, with the expectation that peak train frequencies would be raised again in the future.{{cite news|url=http://web.mta.info/nyct/service/pdf/F_express.pdf|title=Feasibility and Analysis of F Express Service in Brooklyn|date=May 2016|publisher=Metropolitan Transportation Authority|access-date=June 24, 2016|archive-url=https://web.archive.org/web/20160527062554/http://web.mta.info/nyct/service/pdf/F_express.pdf|archive-date=May 27, 2016|url-status=live}}{{cite web|url=http://web.mta.info/mta/news/notices/pdf/Canarsie_Env_Assessment_%20FINAL.pdf|publisher=Metropolitan Transportation Authority|title=MTA New York City Transit Canarsie Tunnel Project Supplemental Environmental Assessment and Section 4(f) Review July 2018|date=July 2018|archive-url=https://web.archive.org/web/20180724213546/http://web.mta.info/mta/news/notices/pdf/Canarsie_Env_Assessment_%20FINAL.pdf|archive-date=July 24, 2018|url-status=live}}

File:M train at Metropolitan Avenue station, December 2017.JPG during reconstruction of the Myrtle Avenue Line's junction with the BMT Jamaica Line|alt=An "M" shuttle train at Middle Village–Metropolitan Avenue during reconstruction of the Myrtle Avenue Line's junction with the BMT Jamaica Line|left]]

From July 1, 2017, to April 30, 2018,{{Cite news|url=http://qns.com/story/2018/04/25/m-train-track-return-full-service-myrtle-ave-ridgewood-next-week/|title=M Train on Track to Return to Full Service on Myrtle Ave in Ridgewood Next Week|last=Kelley|first=Ryan|date=April 25, 2018|work=Queens Courier|access-date=April 27, 2018|language=en-US|archive-url=https://web.archive.org/web/20180425214858/http://qns.com/story/2018/04/25/m-train-track-return-full-service-myrtle-ave-ridgewood-next-week/|archive-date=April 25, 2018|url-status=live}} reconstruction of two sections of the BMT Myrtle Avenue Line—the approaches to the line's junction with the BMT Jamaica Line and Fresh Pond Bridge over the Long Island Rail Road's Montauk Branch in Queens—required a reroute of M service. Trains to and from Manhattan and Queens, instead of diverging at Myrtle Avenue to go to Metropolitan Avenue, continued east on the BMT Jamaica Line and terminated at Broadway Junction at all times except late nights, when service was suspended. A limited amount of rush hour trains ran between 71st Avenue in Queens and Second Avenue in Manhattan, replicating the {{NYCS|V}} train's routing prior to its discontinuation in 2010. Three shuttle bus routes ran during reconstruction of the Fresh Pond Bridge: one between Myrtle Avenue and Fresh Pond Road; the second between Myrtle and Metropolitan Avenues, skipping the Fresh Pond Road station during the daytime hours; and the third between Flushing Avenue/Broadway and Middle Village–Metropolitan Avenue, stopping at Flushing and Wyckoff Avenues for a transfer to the BMT Canarsie Line at Jefferson Street.

When the Fresh Pond Bridge project was completed on September 2, 2017, two six-car shuttle trains began operating between Metropolitan and Wyckoff Avenues at all times, running separately from each other on each of the two tracks; two additional six-car trains were stored in the Fresh Pond Yard in order to swap consists in and out of service.{{cite journal |date=October 2017 |title=Subdivision "B" Car Assignments -- Cars Required September 2, 2017 |url=https://erausa.org/pdf/bulletin/2010s/2017/2017-10-bulletin.pdf |journal=The Bulletin |volume=60 |issue=10 |publisher=New York Division, Electric Railroaders’ Association |pages=6 |access-date=April 13, 2025}}{{cite journal |date=November 2017 |title=New York City Subway Car Update -- Subdivision "B" News |url=https://erausa.org/pdf/bulletin/2010s/2017/2017-11-bulletin.pdf |journal=The Bulletin |volume=60 |issue=11 |publisher=New York Division, Electric Railroaders’ Association |pages=7 |access-date=April 13, 2025}}{{Cite web|date=August 18, 2017|title=Final Phase of M Line Overpass Reconstruction Begins September 2|url=http://www.mta.info/news/2017/08/18/final-phase-m-line-overpass-reconstruction-begins-september-2|url-status=live|archive-url=https://web.archive.org/web/20170824082553/http://www.mta.info/news/2017/08/18/final-phase-m-line-overpass-reconstruction-begins-september-2|archive-date=August 24, 2017|access-date=June 21, 2020|website=mta.info|publisher=Metropolitan Transportation Authority}} These shuttles, along with a shuttle bus route that provided service between Wyckoff Avenue and Broadway, ran until April 27, 2018.{{Cite news|url=http://www.nydailynews.com/new-york/brooklyn/m-line-shut-year-repairs-article-1.2568599|title=M Line to Be Shut Down Next Year for Repairs|last=Rivoli|first=Dan|date=March 17, 2016|work=New York Daily News|access-date=July 23, 2016}}{{Cite news|url=http://www.amny.com/transit/m-line-repairs-will-begin-next-summer-the-mta-said-1.11590899|title=MTA: M Line Will Shut Down for Part of Next Year|last=Brown|first=Nicole|date=March 18, 2016|work=AM New York|access-date=July 23, 2016|archive-url=https://web.archive.org/web/20160320130451/http://www.amny.com/transit/m-line-repairs-will-begin-next-summer-the-mta-said-1.11590899|archive-date=March 20, 2016|url-status=live}}{{Cite web|url=http://web.mta.info/nyct/service/MyrtleAvenue/index.html |website=mta.info|publisher=Metropolitan Transportation Authority|title=Myrtle Avenue Line Infrastructure Projects|access-date=July 23, 2016}}

When the 14th Street Tunnel shutdown started in April 2019, weekend and weekday evening M service (from 11:00 p.m. to 1:15 a.m.) was extended from Essex Street to 96th Street on the Second Avenue Subway in Manhattan, via 63rd Street, to compensate for limited L service between Brooklyn and Manhattan. The M had to run to 96th Street because of capacity reductions on the Queens Boulevard Line due to ongoing weekend construction.{{Cite web|url=http://web.mta.info/sandy/pdf/Canarsie-6-08-17_website.pdf|title=Fixing the L Line's Canarsie Tunnel|publisher=New York City Department of Transportation; Metropolitan Transportation Authority|website=mta.info|access-date=July 27, 2018|pages=18|archive-url=https://web.archive.org/web/20170609201838/http://web.mta.info/sandy/pdf/Canarsie-6-08-17_website.pdf|archive-date=June 9, 2017|url-status=live|date=June 8, 2017}}{{Cite web|url=http://web.mta.info/mta/news/books/pdf/181022_1000_Transit.pdf|title=Transit & Bus Committee Meeting October 2018|date=October 22, 2018|website=mta.info|publisher=Metropolitan Transportation Authority|access-date=October 22, 2018|page=195|archive-url=https://web.archive.org/web/20181020140605/http://web.mta.info/mta/news/books/pdf/181022_1000_Transit.pdf|archive-date=October 20, 2018|url-status=dead}} Both weekday and weekend M frequencies were also increased.{{Cite news|url=http://pix11.com/2017/12/13/l-train-shutdown-to-close-portion-of-14th-street-during-rush-hour-mta/|title=L Train Shutdown to Close Portion of 14th Street to Cars During Rush Hour: MTA|date=December 13, 2017|work=New York's PIX11 / WPIX-TV|access-date=December 15, 2017|language=en-US|archive-url=https://web.archive.org/web/20171214001418/http://pix11.com/2017/12/13/l-train-shutdown-to-close-portion-of-14th-street-during-rush-hour-mta/|archive-date=December 14, 2017|url-status=live}}{{Cite news|url=https://www.nytimes.com/2017/12/13/nyregion/l-train-closing-plan.html|title=Rerouting Thousands: City Plans for L Train Closure|last=Nir|first=Sarah Maslin|date=December 13, 2017|url-access=subscription|work=The New York Times|access-date=December 16, 2017|language=en-US|issn=0362-4331}} This extra service was discontinued after completion of tunnel construction on April 27, 2020.{{cite web|title=Service Information for L, M, G, 7, M14 SBS and Free Transfers|url=https://new.mta.info/l-project/post-tunnel-work-service|access-date=April 26, 2020|archive-url=https://web.archive.org/web/20200426180938/https://new.mta.info/l-project/post-tunnel-work-service|archive-date=April 26, 2020|url-status=live|publisher=Metropolitan Transportation Authority|website=mta.info|date=April 26, 2020}} Weekday evening service after 9:15 p.m. was also indefinitely cut back from Forest Hills to Essex Street to accommodate maintenance work for the installation of communications-based train control on the Queens Boulevard Line, Eighth Avenue Line, and Sixth Avenue Line.{{Cite book|url=https://new.mta.info/document/12066|title=Transit and Bus Committee Meeting November 2019|date=November 8, 2019|publisher=Metropolitan Transportation Authority|pages=69–71|archive-url=https://web.archive.org/web/20200621120117/https://new.mta.info/document/12066|archive-date=June 21, 2020|url-status=live}}{{Cite web|date=November 6, 2019|title=Re: M Line Subway Schedule Changes Effective April 2020|url=https://www1.nyc.gov/assets/queenscb2/downloads/pdf/2019/mta_transit_line_subway_schedule_changes.pdf|url-status=live|archive-url=https://web.archive.org/web/20200621120337/https://www1.nyc.gov/assets/queenscb2/downloads/pdf/2019/mta_transit_line_subway_schedule_changes.pdf|archive-date=June 21, 2020|access-date=June 21, 2020|publisher=New York City Transit}}

Weekend frequencies on the M route were increased in July 2023.{{cite web |last=Izzo |first=Christina |date=May 8, 2023 |title=Changes Are Coming to the G, J and M Trains This Summer |url=https://www.timeout.com/newyork/news/changes-are-coming-to-the-g-j-and-m-trains-this-summer-050823 |access-date=August 27, 2023 |website=Time Out New York}}{{cite web |last=Simko-Bednarski |first=Evan |date=May 2, 2023 |title=NYC Transit Boosting Subway Service on a Dozen Lines This Summer |url=https://www.nydailynews.com/new-york/ny-more-frequent-subway-service-weekend-20230502-mowsr3v2gjhodpvbkcbpfsurf4-story.html |access-date=August 27, 2023 |website=New York Daily News}} Starting August 28, 2023, weekday M trains were truncated to 57th Street in Manhattan, and F trains were rerouted via the 53rd Street Tunnel between Queens and Manhattan, due to track replacement and other repairs in the 63rd Street Tunnel. Weekend M service continued to terminate at Essex Street.{{Cite web|title=Service Changes on the F and M Lines Starting August 28|url=https://new.mta.info/article/service-changes-f-and-m-lines-starting-august-28|access-date=July 30, 2023|website=MTA|language=en}}{{cite web | title=F, M changes start Monday: What to know about the subway interruptions lasting until 2024 | website=NBC New York | date=August 25, 2023 | url=https://www.nbcnewyork.com/news/local/f-m-changes-start-monday-what-to-know-about-the-subway-interruptions-lasting-until-2024/4624625/ | access-date=August 26, 2023}} Service to Forest Hills resumed on April 1, 2024.{{cite web | title=MTA Announces Regular Service Being Restored to F and M Lines Following Critical Track Replacement Work in Manhattan and Queens | website=MTA | date=March 19, 2024 | url=https://new.mta.info/press-release/mta-announces-regular-service-being-restored-f-and-m-lines-following-critical-track | access-date=March 20, 2024}}{{cite web | title=F, M service returning to full service in Manhattan and Queens: What to know | website=NBC New York | date=March 19, 2024 | url=https://www.nbcnewyork.com/news/local/f-m-service-returning-to-full-service-in-manhattan-and-queens-what-to-know/5241120/?amp=1 | access-date=March 20, 2024}}

{{Plain image with caption|File:MJ Train (1967-1979).svg|Short-lived MJ logo from 1967 to 1969|75px}}File:Myrtle Av Line stub vc.jpg

On March 5, 1944, 11 trains stopped running over the Brooklyn Bridge, instead ending at Bridge–Jay Streets on the Brooklyn side, and all 11 trains terminated there (with a free transfer to the IND trains at Jay Street–Borough Hall).{{Cite news|url = https://www.newspapers.com/image/52688587|title = Brooklyn Bridge Train Service Ends Today—Trolley Cars Stay On|date = March 5, 1944|access-date = January 24, 2016|work = The Brooklyn Daily Eagle|page = 11}} In 1967, when the Chrystie Street Connection opened, the label MJ was assigned to the 11 service.

The western half of the Myrtle Avenue Line closed on October 4, 1969, ending MJ service, which was replaced with a free transfer to the B54 bus.{{cite web|url = http://www.thejoekorner.com/scripted-ticket-display.shtm?http://www.thejoekorner.com/brochures/myrtle.gif|title = Service Changes for Myrtle Avenue "El" Riders|date = October 1954|access-date = January 24, 2016|website = joekorner.com|publisher = New York City Transit Authority}} Several days before the scheduled closing date, some supports for the elevated structure were hit by a truck, temporarily suspending service. Timber reinforcement was applied to damaged pillars, allowing service to resume until the scheduled closing date.{{cite web|url=http://www.thethirdrail.net./images/myrt_truck.jpg|title=Damages structural column #64 shored up shortly before abandonment. Hit by truck, Photo on 10/3/69}}

The following table shows the lines used by the M, with shaded boxes indicating the route at the specified times:{{NYCS const|serviceguide}}

For a more detailed station listing, see the articles on the lines listed above.The M train runs on the following lines:

{{NYCS service legend

| alltimes = show

| allexceptnights = show

| nightsonly =

| nightsweekends =

| weekendsevenings = show

| weekdaysonly = show

| allexceptrush =

| allexceptweekdays = show

| dailyexceptrush =

| rushonly = show

| rushpeak =

| closed = show

| custom_icon_1 = rushpeak

| custom_text_1 = Stops rush hours/weekdays in the peak direction only

| custom_icon_2 =

| custom_text_2 =

}}

{{Reflist|30em}}

{{commons category|M (New York City Subway service)}}

• [http://web.mta.info/nyct/service/mline.htm MTA NYC Transit – M Sixth Avenue Local]
• {{NYCS const|traintime|M}}
• {{NYCS const|timetable|M}}

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Category:New York City Subway services