Most online mapping products today feature transit directions. Sadly, though, it's the nature of public transit that things often don't quite run on schedule. Thankfully, quite a few transit district have now track their buses and trains with a GPS system so that the public can know exactly when the next bus or train will arrive. For the most part, however, you won't know this information until you arrive at the station (which is always either far too early or just too late). Starting today, however, there's a better way to get this information quickly: Google Maps will now feature live transit updates in four U.S. cities (Portland, OR, Boston, San Diego and San Francisco) and two European ones (Madrid and Turin).