Should the US invest in high-tech rail or skip it and go directly to self-driving cars?

I’d like to see better passenger rail options in the US, but I wonder if a system of self-driving cars would make improved passenger rail unnecessary. I’m hearing more talk about self-driving cars these days but don’t know how close the technology is to implementation on a large scale.

Given that funds are limited, does it make sense to invest in both self-driving cars and next-generation rail? If we can’t have both in the next 20 years or so, which would be the better investment?