Transit directions would be a major new feature to Apple's Maps application in iOS 9. The new directions, which were reportedly supposed to debut last year with iOS 8, but didn't make the cut ahead of WWDC. Apple's transit directions will apparently include subways, trains, and buses, according to 9to5Mac:

Sources said last year that the transit functionality for Maps includes larger icons for users to more quickly spot airports, subway stations, and train stations within the Maps app. In addition to the main functionality, there is also a trip planning feature for transit, and a new Transit view alongside the existing Standard, Hybrid, and Satellite/Flyover views.

Apple has also apparently been making progress on indoor mapping. The feature would allow Apple to help people navigate large buildings and offices, and the company acquired indoor location startup WifiSLAM in 2013, presumably for this purpose. Apple is currently said to be deploying autonomous, iBeacon-equipped robots in order to map their Cupertino offices.

Source: 9to5Mac