Rail is complicated for different reasons. Technology isn’t the problem with rail. It’s the cost, getting the right of way, nimbyism, politics, environmental, and so on.

Have you ever seen a rail line built? They’ve been building a light rail line near my house since before I moved in 12 years ago and it’s not scheduled to finish for another 2 years. Funding and engineering went on for years before that.

Whatever new tech we need to get the trucks following each other will be done before this rail line. I think the technology is pretty close already. My wife’s 2016 Subaru has adaptive cruise control and lane assist which seems like enough to draft a semi.