In the Metro Detroit area, Apple Maps routing supports DDOT and SMART buses, the Detroit People Mover, the Michigan Flyer, and Amtrak. Limited navigation extends to a number of Detroit suburbs in Oakland, Macomb, and Wayne Counties, including Ann Arbor, Dearborn, Pontiac, Sterling Heights, and Warren.
In the Windsor, Ontario area, Apple Maps routing supports Transit Windsor buses. Navigation extends to immediate suburbs in Essex County such as Tecumseh, Ontario. Tunnel Bus routing is also available for cross-border trips between Windsor and select locations in the Metro Detroit area.
Apple introduced Transit in Maps as part of iOS 9 in select cities around the world, including Baltimore, Berlin, Boston, Chicago, London, Los Angeles, Mexico City, New York, Philadelphia, San Francisco, Sydney, Toronto, and over 300 cities in China. The feature has its own tab in Apple Maps on iOS 10 for entering directions.
Transit continues to expand to several other cities, including Atlanta, Columbus, Dallas, Denver, Honolulu, Houston, Kansas City, Melbourne, Miami, Minneapolis–Saint Paul, Montréal, New Orleans, Pittsburgh, Portland, Prague, Rio de Janeiro, Sacramento, Salt Lake City, San Antonio, San Diego, Seattle, Vancouver, and Victoria.
(Thanks, Bernd and David!)