When set in Directions mode, Maps now offers three icons — car, public transit, and walking — centered at the top of screen, in between the “Edit” and “Start” buttons. Selecting the transit icon provides a list of transit choices that can include subways, buses, or a combination of the two.
A list of departure times and estimated commute times accompany each transit option. Once you select a particular method of transit, the Maps application will serve up step-by-step directions from your current location, usually directing you to your chosen departure subway or bus stop on foot. During commutes, Maps will specify when you should board or disembark from a bus or train.
Read the full article for screen shots and more information.
My comments: Although each local transit agency (and transit-supportive local web sites) may offer tools more directly tailored to a locale, this effort by Google and Apple will provide a valuable tool for frequent travelers with a consistent interface, and the additional visibility this provides, just from a PR perspective, may prod more transit agencies to provide real-time and schedule data to service providers like Google.