I was in high school 20 years ago, and a robotics nerd, and back then it definitely didn't seem "several centuries away." The DARPA grand challenge was back in 2004.

Twenty years ago they had prototype self-driving cars. They sucked, but they were good enough that planning started for the DARPA Grand Challenge. Some of the winners were hired by Google and became Waymo. They've been working on this for a long time.

20 years ago was 1999. I think that it was very easy to imagine self-driving cars being within a few decades' reach back then. Not much harder than to imagine it today.

Most of the talk of self driving cars was always on purpose built lanes/roads. That certainly has been in discussion for 50 years.

I remember there being an example around that area of a caravan of cars that could drive themselves.