Subway Lines

Open Data Portal

The NYC Department of Information Technology and Telecommunications Geographic Information Systems group maintains a subway lines dataset for use on cartographic products. It's not spatially accurate - editors have used cartographic license to manually separate and generalize lines.

https://data.cityofnewyork.us/Transportation/Subway-Lines/3qz8-muuu

Center for Urban Research at the Graduate Center/CUNY

A parallel effort at the City University of New YorK.

https://www.gc.cuny.edu/Page-Elements/Academics-Research-Centers-Initiatives/Centers-and-Institutes/Center-for-Urban-Research/CUNY-Mapping-Service/Projects/NYC-Subway-GIS-update-Hudson-Yards,-7-Line-Extension

GTFS Data From The Metropolitan Transportation Authority

Good luck. You must accept the counter-intuitive terms to plunge down this rabbit hole.

http://web.mta.info/developers/developer-data-terms.html#data

A description of the challenges using Google Transit Feed Specifications data for subway lines:

https://spatialityblog.com/2010/07/08/mta-gis-data-update/