When you talk about autonomous cars (or automated, or self-driving, or driverless cars), do you really mean vehicles? If so, say vehicles. The word cars (or taxis) explicitly excludes transit (as well as trucks and many other vehicles).
As a transit planner, I’m routinely told that we should neglect our transit systems, and certainly not improve them, because transit will soon be made obsolete by “autonomous cars.” There are very low density places where this is true, but it is geometrically impossible for dense cities, because there is simply not room to move everyone out of big transit vehicles into the tiny ones that the word “cars” implies.
However, the fantasy of cars replacing big transit vehicles can lead to serious dystopian outcomes, including higher Vehicle Miles Traveled, higher emissions, and higher exclusion of disadvantaged groups from opportunity. The fantasy is already encouraging neglect of transit systems and opposition to efforts to improve them, which is having all the negative impacts listed above, today.
None of these problems arise if the tech proponents would consistently speak of “autonomous vehicles.” In that case, the notion of autonomous vehicles replacing transit wouldn’t even arise, because it’s obvious that transit is made of vehicles too, and that the automation of transit vehicles would be part of any long-term automation project.
When I press an autonomous-car advocate on this point, they almost always say that of course autonomous vehicles will come in all sizes, including transit vehicle, etc. But they keep saying autonomous cars, which implies the opposite.
Remember, many people hate transit, love cars, and are generally OK with all the outcomes of mandatory car dependence, especially sprawl. These people love to hear that autonomous cars will destroy transit.
But if you talk about autonomous vehicles, you can promote autonomous technology without sounding like you’re advocating cars over transit, with all the problems for big cities that this implies. Why not do that? You’ll provoke less blowback from urbanists, and have more friends.