I think the first major tipping point is going to be electric buses. They run relatively short, well-known routes, they have lots of space for batteries as a re

I think the first major tipping point is going to be electric buses. They run relatively short, well-known routes, they have lots of space for batteries as a replacement for the big diesel engine, they can have a charging pantograph on the roof without seeming ugly (unlike on a passenger car), and they can trickle charge for 5-10 minutes at either end of their route, keeping them topped up enough to last a full day of driving. In addition, they're also quieter, have less vibration and don't produce local pollution in the form of diesel exhaust, which modern buses have lots of costly systems installed in order to mitigate. All public transit should be electrified, to set a good example.