Editing Line 4 Sheppard (section)

===Westward extension===
[[File:Downsview_Station_Bus_Platforms.jpg|thumb|[[Sheppard West station]] would be the western terminus of the proposed extension]]
A separate {{convert|4.5|km|mi|adj=on}} westward extension was proposed to Sheppard West station on Line 1. Lower population density made this expansion a much lower priority than the eastward one, as the minimal increase in ridership was insufficient to justify the costs. The approval of the Spadina subway extension to the [[Vaughan Metropolitan Centre]] in [[Regional Municipality of York|York Region]] renewed interest in this phase, as a subway connection between Sheppard West and Sheppard–Yonge stations would significantly lower commuting times for [[York University]] students, as well as commuters travelling to and from Vaughan Metropolitan Centre. The tunnel from Sheppard–Yonge station to Welbeck Road (one block east of Senlac Road) was built for train storage at the time of original construction.<ref>{{Cite news |last=Kelly |first=Malcolm |date=August 12, 2000 |title=Some call it the 'Subway to nowhere.' Mel Lastman knows better |work=[[National Post]] |quote=That tail quietly wags all the way to Welbeck Street, four blocks away.}}</ref> In December 2009, a westward extension was again considered by the TTC to link the line to the [[Wilson Yard|Wilson subway yard]]. It was immediately dismissed due to cost.<ref>{{Cite web|url=http://www3.ttc.ca/About_the_TTC/Commission_reports_and_information/Commission_meetings/2009/December_16_2009/Reports/Yonge_University_Spa.pdf|title=TTC Report December 16 2009|access-date=December 14, 2009|archive-date=February 25, 2021|archive-url=https://web.archive.org/web/20210225162907/http://www.ttc.ca/About_the_TTC/Commission_reports_and_information/Commission_meetings/2009/December_16_2009/Reports/Yonge_University_Spa.pdf|url-status=live}}</ref> In December 2013, this extension was listed as being under consideration as an "unfunded future rapid transit project" in the City of Toronto's "Feeling Congested?" report.<ref>{{Cite web|url=http://www.toronto.ca/legdocs/mmis/2013/pg/bgrd/backgroundfile-64550.pdf|title=Toronto Feeling Congested? report|access-date=July 20, 2016|archive-date=April 4, 2016|archive-url=https://web.archive.org/web/20160404003538/http://www.toronto.ca/legdocs/mmis/2013/pg/bgrd/backgroundfile-64550.pdf|url-status=live}}</ref> {{as of|2019|04}}, the westward extension had neither provincial government support nor funding.<ref name="CBC-2019-04-04" />

At its February 20, 2020, meeting, the Metrolinx board of directors endorsed a prioritization framework for a proposed frequent rapid transit network that was inclusive of a proposed subway extension from Sheppard–Yonge station to Sheppard West station; with a forecast ridership of 9,800 per hour in 2031 and a proposed line length of {{convert|4.3|km}} along Sheppard Avenue West, the project scored "medium" with a preliminary benefit-cost ratio of 0.26 to 0.35.<ref>{{Cite web |title=Metrolinx Project Prioritization |url=https://www.metrolinx.com/en/regionalplanning/projectevaluation/projectprioritization/project_prioritization.aspx |access-date=November 2, 2022 |website=www.metrolinx.com |archive-date=October 16, 2022 |archive-url=https://web.archive.org/web/20221016091055/https://www.metrolinx.com/en/regionalplanning/projectevaluation/projectprioritization/project_prioritization.aspx |url-status=live}}</ref>

In November 2023, Metrolinx announced preparation of an initial business case for Line 4 extensions, and that Metrolinx was also considering a westward extension of Line 4 to Sheppard West Station.<ref>{{Cite web |title=Sheppard Subway Extension Consultation - November 2023 |url=https://www.metrolinx.com/en/projects-and-programs/sheppard-extension/events/sheppard-extension-consultations |access-date=2024-12-11 |website=www.metrolinx.com |language=en}}</ref> In June 2024, Metrolinx held several public consultations with routing concepts.<ref name=":2" />