[mike47]

The idea of a magnetic coupling between the engine and the passenger compartment is very interesting. This could be adapted to use with self-driving automobiles on highways. They could run on their own electric power train for local journeys, then pick up a "thrust carriage" when joining a highway. This pulls them along until their exit, when they decouple and return to using their battery and on-board motors. The on-board motors could also take over for short sections for example between different thrust carriage runs.

Perhaps the thrust carriage control systems could be made smart so they automatically maintain safe spacing between vehicles and adapt their speed to the volume of traffic. They'd communicate with the vehicle to tell them when the coupling was about to end so that the vehicle can engage its own drive train to take over smoothly. Or the vehicle's self-driving systems tell the thrust carriage how fast to go depending on the traffic conditions.

This could massively extend the range of electric cars. Burying the pipes in the road network would obviously be very expensive, but the size mentioned in the article (12 inch diameter) is not prohibitive.

[avar]

You wouldn't need a thrust carriage to get big fuel gains. It's enough that the cars form a tightly packed line as racing cyclists do to minimize drag to get major gains is fuel economy:

https://www.quora.com/How-much-does-aerodynamics-affect-fuel...

[mike47]

The changes in fuel economy mentioned in that article don't seem that big. On the other hand, if an electric car only needed batteries for a range of say 50km, that would be a large saving in cost and weight. The batteries are only needed for local journeys, and the thrust carriage mechanism provides almost all of the energy for long journeys.

It would probably require electrically driven thrust carriages rather than pneumatic - you would need one for every car using the system. Trucks might need 2 or 3 or more to provide enough thrust. If a magnetic coupling really works, it would be possible to attach and detach from the thrust carriage at motorway intersections without slowing down any more than cars do at the moment.

[quintushoratius]

> It would probably require electrically driven thrust carriages rather than pneumatic - you would need one for every car using the system.

Not necessarily one per car. You'd probably have a chain of thrust carriages, with maybe some spacing in between each individual carriage. One or several cars would clump onto a thrust carriage -- there's nothing to prevent them from being quite long.

When it's time to get off the highway there might be a hole in the clump for a bit until someone getting onto the highway fills it in.

The one issue I see is that, in order to disconnect from the thrust carriage, you have to have a way to do so. The logical method is to use an electromagnet that can be powered on/off to connect/disconnect but then the car has to power that -- and that might sap it's range a bit.