I'd take issue with your definition of "easy". Even if we had self-driving cars today, it would still be a matter of a phone call to get major traffic arteries closed, whereas there's no guarantee that any group of individuals could work out a way to turn off the cars. You're comparing a known, implemented process with a hypothetical possibility. Similarly, terrorists _could_ conceivably hack their way into a traffic control system, but it's a lot more likely they'd simply try to take over a plane with brute force.

This is similar to "tin hat" theories: they favor the dramatic and insidious, but unlikely, fear over the much more imminent and mundane problem.

I'm more than willing to give up the right to absolute control over my vehicle in return for better safety and faster commutes. The lives saved in both time and accidents would far outweigh the remote possibility that it would be used as an instrument of oppression. Maybe folks can control their own vehicle when off of major arteries, but be required to give up control on heavily shared routes (the same as they have to when taking public transportation.)