[Bicycle Bob]

We all know that two cars following each other with just a little gap are "drafting" and can go faster or save fuel. We also know that it takes great concentration to do this safely. However, for a robot, there's plenty of response time available.
So, let's equip cars with tranceivers fore and aft, using a bit of common software so that we can draft other cars similarly smartened up, and form trains for even more economy. We could leave the driving to the person in front, and catch up on screen time while waiting for our freeway exit. A button would notify our neighbours that we would be changing lanes. We might get the option of watching the dash cam of the lead car, and put on our brakes for any emergency. If the response times got tougher on a long train, an emergency braking signal could be added, with the expense of a mechanical activator.

If this gets popular, the highways might also be given some smarts. You could cruise down an on-ramp, and then either pace an accelerating light on the guard rail, or turn over control (easier with electrics) and let the system neatly slot you into the first passing gap.