In my opinion, people should change as quickly as possible, I think thats going to be extremely important for humans across the board moving forward.
That said, I dont know how to apply that thought societally, everyone has different tolerances. And also, most people I meet resist change without thought, so my guess is it would be incredibly slow as everyone would be mostly concerned with making sure its not an inconvenient solution.
Just giving it a few minutes thought here, I want to say this is a problem that should be solved by local government, as that would be the largest scale where you could vary the approach by specific population needs.
Maybe some farm heavy states are going to essentially need most of their vehicles, who knows.
Probably first we need to all agree on the problem though…
Edit: idea! Maybe use federal government to set the goals and direction we should be heading in, and let local governments handle the how and how much a d how fast.