Amtrak has run buses forever. Sometimes it's one-off, to rescue passengers from a broken train. But it's also to provide connections to trains it runs from off-line locations.

Usually, you can only ride the bus if you have a train ticket for some portion of the trip, if Amtrak actually runs it (by itself, or through some state agency that supports the train service). They're usually reserved-seat only; you need to have bought a train ticket that includes the bus segment ahead of time. There are exceptions, of course. Amtrak-operated buses are usually guaranteed connections: if the train is late, the bus waits, and vice versa.

Often, it's a regular bus run by somebody else that accepts an Amtrak ticket as the fare. That way, you can buy the whole trip at once, from Amtrak. Don't expect any discounts on the local bus fare for that! And these buses are usually NOT guaranteed connections - they have a schedule of their own to meet, and won't wait for the train, and vice versa.

Amtrak timetables will sometimes note, for the second type of bus, that they're "operated by ..." You can then search for that agency's or company's web site to look up the schedule and plan for any alternatives you might need if the train is late.

For examples, Capitol Corridor in California runs a lot of connecting buses, some on route of many hours, connecting with it trains (and other Amtrak trains, as well, at certain stations). They run so many that they have separate train and bus timetables. See [www.capitolcorridor.org] and click on Schedules.