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Riders of public transportation in New York and Salt Lake City are the first to get real-time departure info in Google Maps. Washington, D.C. residents will also get a bit of new live transit info.

Live departures as seen on an Android phone. Devin Coldewey / NBC News

Everyone knows the triumph and exasperation of making and missing a train by a few seconds. And having your phone be able to tell you whether the 5:15 is on time or 2 minutes late is something for which millions have no doubt wished.

The latest update to Google Maps makes that dream a reality, if only for a select few in the country for now. NYC's 1-6 subway lines should give live departure times, indicated on the map by a blinking circle. Several Salt Lake City buses and trams, too, are getting real-time updates.

Washington, D.C. doesn't get quite the level of detail as the others, but global delays, track work and other service alerts will be integrated with transit schedules and directions.

No indication was given in Google's blog post announcing the features whether or when other cities can expect similar features. Google Maps transit info is available for hundreds of cities around the world, however, so there's no shortage of demand — though metro authorities must assemble and provide the necessary information in order for Google to include it.

The updates are live now on the Web and mobile devices.

Devin Coldewey is a contributing writer for NBC News Digital. His personal website is coldewey.cc.