I'm going to write more in the future about how transportation is not making using technology. Let me start with streetcars and the bus.
People use transit a lot more if it is able to beat the car, or at least keep pace with it. Thus we spend a lot of money on dedicated right-of-way for subways, trains and streetcars.
But this is really inefficient. The dedicated right-of-way sits empty 95% of the time. It does nothing so that a train can pass over it every 10 minutes (or more.)
Imagine a system where street cars and electric bus lines run on regular city streets. But it's illegal to drive in front of the car or bus in its special lane. It's OK to drive behind it, but if the car or bus ever has to hit the brakes because you're in front of it, it snaps a picture of the plate, and your car is sent a ticket for $200 for blocking the lane.
The main downside I see to this is the risk of people pulling dangerous stunts to get out of the lane, trying to merge into heavy traffic in the next lane to avoid the fact ticket when they see a bus coming up behind them. The system would have to be tweaked and tested to avoid that, with bigger tickets for making an unsafe lane change etc.
Large carpools (4 or more) might also be allowed in the lane, private busses, shared taxis and so on. Of course, once the streetcar went past, people would zoom behind it to follow its speedy course. But that's good. It's far more efficient than dedicated right-of-way, but gets near the speed.
Traffic signals would of course have to be coordinated with this, stops somewhat limited and there would probably remain some dedicated right-of-way in certain areas. We won't tear out our subways to make this happen.