The MBTA does this these days although its main use is w/ the busses, where it has been a godsend. Since the bus tracking apps arrived busses went from somethin

The MBTA does this these days although its main use is w/ the busses, where it has been a godsend. Since the bus tracking apps arrived busses went from something I actively avoided taking to using all the time to navigate the spokes in the system for exactly the reason you state. I can watch from my computer or phone until just before a bus is coming in and hurry on out to the stop.