I think it comes down to cost. Its only effective in very dense areas. For example, right now I'm on an established commuter rail line going from downtown to a suburb. I'm paying $12 round trip to travel 60 miles total. It's just barely cheaper than driving (not including parking expenses).
At this point in time, I think it's wise to avoid laying costly new tracks with the dawn of driverless cars on the horizon.
At this point in time, I think it's wise to avoid laying costly new tracks with the dawn of driverless cars on the horizon.