To me buses and truck market seems niche as compared to personal cars for companies looking to build electric tech to drive them. Number of state departments and businesses willing to pay for electric vehicle are fewer compared to electric car customers.
And airlines are niche compared to mass market cars too, but they're still a good business!
One thing I think most people don't appreciate is that the switch to self-driving cars will transform America into a mostly-transit society. Once you don't need a car to live from day to day, you sell it. Then you take a self-driving Lyft from your house to the bus depot, train station, or airport.
The market for self-driving busses between cities will grow alongside the market for self-driving cars within cities.
If self-driving taxis are ubiquitous enough, there could be very little wait time between hailing a taxi from an app on your smartphone and the taxi arriving at your location.
At some price point, it will stop making sense to spend $20,000-$30,000 to buy a car. And you won't have to pay for insurance or gas or wear-and-tear or parking. The car could be out making money instead of being parked 22 hours a day.
Businesses and apartments and home developers will stop building parking spaces and parking lots once self-driving taxis hit a sufficient threshold.
Finally, cars will solve transit's "last mile" problem. Instead of paying for a taxi from home to work, you can pay for a taxi from home to the Light Rail station.