I think it could be a very good thing, and one that could evolve incrementally from existing technologies.
I imagine ‘Road-Trains’ as made up of cars on highways that automatically adapt to what cars in front of it are doing, and can follow more safely, and at closer distances, than when people are more in control.
A Road-Train is a column of cars flying down the highway, at very high speed and close together. Because each car could ‘draft’ the other cars, as bicycle teams ride in close formation do, the would get much improved gas mileage because only the first car would face the inefficiency of breaking the wind that is now the blight of every car on the road.
Drivers would have to explicitly engage and disengage from the ‘train’, but their cars would signal the other cars, and their drivers, that this is what they are interested in doing, so wider spaces could be created and signals to help the driver match speed.
These actions could be made as safe as how we presently change lanes on a highway, which we do all the time, but in this case, it would happen much more rarely since once you are in a Road-Train, then your car can help you drive.
We could think of merging into a Road-Train like a highway entrance ramp: we have to speed up, match speed, and merge in. Alerting the drivers in the cars ahead and behind that something is going on, so they should pay more attention.
Google said that people engaging manual controls unpredictably was a problem : “Google said its testing had suggested it was safer to remove conventional controls altogether because the results of a human having to take over suddenly and unexpectedly were unpredictable and potentially dangerous.” Therefore the Road-Train would make the engaging of manual controls a predictable and supported feature, and one that would only be needed when engaging and disengaging from a Road-Train.
Leaving a Road-Train would be done by a signal, like a turn signal, and the cars would again alert each other, create a wider space, and let the driver safely engage manual control and leave.
Cars have almost all the technology needed– They know how to stay in a lane . They now apply brakes automatically to avoid collisions. Cars can talk to each other to alert them. So this Road-Train is almost ready from technology perspective. And a Road-Train would leverage Google’s experience to minimize the number of times people have to take manual control or release control of the car.
The result could be much greater gas efficiency because of drafting. Further, we could safely increase the density of cars on the road. Since these cars would be both closer together and going faster, the road throughput would be much higher. Therefore we would have much fewer traffic jams, or thought of another way, our traffic jams would be going at full speed.
Another advantage would be the time we spend in our cars could be more productive because we would not need to be as attentive to the road– we could do many of the things people are already doing, but safely– texting, reading, talking. It could be like having a custom railway car, going very fast, and delivery you right to your door.
Car-pool lanes could be dedicated Road-Train lanes for all the right reasons: better fuel efficiency, and higher density. It would reward those that have Road-Train-ready cars, but not require a cut-over from non-equiped cars. Thus a smooth transition could be made and also give those of us that like manual controls a way to say in control, when we want to be.
I would much prefer being in a Road-Train for a long driver, or even commuting.
All aboard the Road-Train!