The Google Maps tech team has a question: "Have you ever arrived at a subway platform only to find that the train you intended to take is skipping stops, rerouted on another line, or isn't running at all due to scheduled maintenance?" Heavens no, wouldn't THAT be aggravating? Well, in the unlikely event that the MTA needs to reroute a train over another line or bypass a series of stations, Google Maps has you covered:

Now when you click on any of the 468 New York City subway stations labeled on Google Maps, you’ll see whether any planned service changes are expected to affect that station at the time. In addition, the relevant alerts will be included in the step-by-step transit directions pointing you wherever you’re going. If you’re looking to find the best route to see a concert after work or checking for any expected delays when already running late, this feature works when you’re online via maps.google.com and Google Maps for Mobile on Android. To adjust your travel around the alerts you see, simply choose another suggested route or change your departure time.

So, to be clear, the Maps interface only shows planned service changes, and won't alert you to unplanned changes, like when an opossum shuts down the D train or Hot Hot Hot Daddy causes the Q to overheat. We asked Google if that kind of integration is on the horizon, and we'll update if we hear back.

UPDATE: Asked about the possibility of real time service info, Sean Carlson at Google says, "We're always looking for ways to improve the experience of transit riders using Google Maps, including more real-time information where available. Transit agencies can help by providing their real-time transit data in open, structured formats such as GTFS-realtime, a common data specification which enables us and other developers to quickly incorporate real-time information into transit applications.