What would be the easiest method?
My guess is that GPS would be the easiest way. It would give you continuous updates regardless of where the shuttles are. You could use software to calculate the time of arrival at different stations and provide this information to riders via a mobile app. The only reason not to use RFID would be if the shuttle buses spend a fair amount of time in parking garages, under buildings or in other places where a GPS transmitter is unable to communicate with GPS satellites. In that case, you could use RFID or a combination of RFID and GPS (there are hybrid devices with both technologies).
With an RFID system, you would place a reader at each bus stop and perhaps on poles along the route. Each time a bus passed, the reader would interrogate the tag on the bus and send that information back to a host system that would update the location of that specific vehicle. The infrastructure involved in installing readers at bus stations (you would need to protect them from the elements and run power out to them) would be prohibitively expensive. This is why I recommend GPS over RFID for this application.
—Mark Roberti, Founder and Editor, RFID Journal
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