Editing Red Line (MBTA) (section)

== Operations and signaling ==
[[File:Red Line tunnel looking north from South Station Feb 2025.jpg|thumb|Reverse curve in the Boston Red Line tunnel between South Station and Downtown Crossing, looking northwards from South Station, showing the emergency crossover.]]
{{As of|February 2023}}, both branches were scheduled to operate on 12–13-minute headways during weekday peak hours (with a combined 6-minute headway between Alewife and JFK/UMass) and 12 to 16 minute headways at other times. Fleet utilization ranged from 16 trains (96 cars) on weekends to 20 trains (120 cars) at peak hours.<ref name=roster2023>{{cite magazine |magazine=Rollsign |publisher=[[Boston Street Railway Association]] |date=January–February 2023 |issue=1–2 |volume=60 |title=MBTA Vehicle Inventory as of February 28, 2023 |first=Jonathan |last=Belcher |page=7}}</ref> However, rolling stock availability and longer trip times due to [[slow zone]]s reduced service. By July 2023, headways were 18 minutes on each branch on weekdays and every 22 minutes on weekends.<ref>{{cite web |url=https://cdn.mbta.com/sites/default/files/media/route_pdfs/batch_6559/SUBWAY-S3-P4.pdf |title=Rapid Transit |date=July 2, 2023 |publisher=Massachusetts Bay Transportation Authority}}</ref> This was improved to 14–16 minute weekday headways and 20–22 minute weekend headways on August 27, 2023.<ref>{{cite web |url=https://www.mbta.com/service-changes/fall-2023-service-changes |title=Fall 2023 Service Changes |date=August 2023 |publisher=Massachusetts Bay Transportation Authority}}</ref>

The Ashmont and Harvard branches were both built with [[automatic block signaling]] and [[Train stop|trip-stop train protection]], while the Braintree and Alewife extensions of the 1980s were constructed with [[Automatic Train Control]] (ATC) using audio frequency [[cab signaling]]. In 1985 the entire Red Line was converted to the new cab signal standard with any remaining [[interlocking tower]]s being closed with a relay based [[centralized traffic control]] machine being installed in a dispatch office at 45 High Street.  This in turn was replaced in the late 1990s with a software-controlled Automatic Train Supervision product by [[Union Switch & Signal]], subcontracted to Syseca Inc. (now ARINC), in a new control room. Subsequent revisions to the system were made internally at the MBTA.{{citation needed|date=August 2015}}

Scheduled [[headway]]s were as low as 2 minutes after the 1928 extension to Ashmont.<ref name=1928report>{{cite book |url=https://archive.org/details/annualreport1928trans |title=Report of the Transit Department for the Year ending December 31, 1928 |year=1929 |publisher=City of Boston |author=Boston Transit Department |page=[https://archive.org/details/annualreport1928trans/page/40 40] |via=Internet Archive}}</ref> When [[Harvard station#Stadium station|Stadium station]] was in use for Harvard football games, headways as low as 1{{frac|3|4}} minutes were used.<ref>{{cite journal |url=https://archive.org/stream/electricrailway411913newy#page/410/mode/2up |title=Recent Improvements of the Boston Elevated System |pages=411–413 |via=Internet Archive |date=March 8, 1913 |journal=[[Electric Railway Journal]]|volume=41 |issue=10 |publisher=Mcgraw Publishing}}</ref> Ridership peaked around 1947, when passenger counters logged over 850 people per four-car train during peak periods. After the conversion to ATC, throughput in the downtown corridor was 13 trains per hour or a little less than 5 minute headway which gives a maximum capacity of 20,280 passengers per hour.<ref name="MBTA-Study">{{cite web|title=Red Line Customer Capacity Update|url=https://willbrownsberger.com/wp-content/uploads/2016/09/Red-Line-Capacity-Constraints-Sept-19-update-3.pdf|access-date=2019-11-12}}</ref>

In October 2018, the MBTA awarded a $218 million improved signal contract for the Red and Orange Lines, which will allow 3-minute headways between JFK/UMass and Alewife beginning in 2022.<ref>{{cite press release |url=http://blog.mass.gov/transportation/mbta/mbta-awards-signal-upgrade-contract-for-red-and-orange-lines/ |title=MBTA Awards Signal Upgrade Contract for Red and Orange Lines |publisher=Massachusetts Department of Transportation |date=October 2, 2018 |first=Klark |last=Jessen |access-date=October 2, 2018 |archive-date=October 10, 2018 |archive-url=https://web.archive.org/web/20181010185351/http://blog.mass.gov/transportation/mbta/mbta-awards-signal-upgrade-contract-for-red-and-orange-lines/ |url-status=dead }}</ref>  The decreased headway will be achieved through increased vehicle performance, an upgrade of the existing ATC system to use higher performance digital components and a reduction in the length of signaling blocks to 500 feet.<ref name="MBTA-Study"/>

During snowstorms, the MBTA runs an empty train during non-service hours to keep the tracks and third rail clear.<ref>{{cite news |url=http://www.boston.com/yourtown/boston/downtown/gallery/mbta_red_line_turns_100?pg=35 |title=MBTA Red Line's 100th anniversary |author=Ba Tran, Andrew |newspaper=Boston Globe |date=23 March 2012 |access-date=29 March 2012}}</ref> The Red Line experienced major service disruptions in the winter of 2014–15 due to frozen-over third rails, leaving unpowered trains stranded between stations with passengers on board.{{citation needed|date=August 2015}}

{{anchor|Equipment}}