Let's make a train

[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.

[freebeard]

Opaque the windshields and make every intersection a circle-8 race.

I imagine a road-train like that in the right lane and my humble little Superbeetle in the left lane wanting to take an upcoming offramp.

[Bicycle Bob]

Trains would have to be in the leftmost lane (right in England) but we would not need nearly as many lanes. If there were trains in an intermediate late, they could be kept slower, and short enough to allow merging through in the space between exits.

[Piotrsko]

Most of the hardware is currently in the new vehicles that "automatic" anything including comm. Software to connect the chain is what's missing.

Not like they move the offramps a couple of miles during the night. Miss Garmin whines at me for 3-5 miles (minutes) about upcomming direction changes. A 3 lane dash across the road to make the exit at the last minute shows a serious lack of driving or planning capacity

[aerohead]

They certainly ought to be in our future.
In 1969, in a NASCAR, two-car draft:
* the Cd 0.315 lead car, falls to Cd 0.22.
* the trailing car is at Cd 0.185.
--------------------------------------------------------------------------------------
In 1987, Hans G'o'tz, of Daimler-Benz reported, for a three-bus NASCAR draft:
* the lead, Cd 0.50 bus was down to Cd 0.425.
* the middle bus was down to Cd 0.167.
* and the trailing bus was down to Cd 0.146.
--------------------------------------------------------------------------------------
Train 'arithmetic' is delicious!

[redpoint5]

Interesting, so middle of the pack isn't as beneficial as last?

[ksa8907]

IEEE 802.11p is an approved amendment to the IEEE 802.11 standard to add...This includes data exchange between high-speed vehicles and between the vehicles and the roadside infrastructure...
https://en.m.wikipedia.org/wiki/IEEE_802.11p

[aerohead]

Originally Posted by redpoint5

Interesting, so middle of the pack isn't as beneficial as last?

Yeah. Weird! It could be that these combinations are so long that, the tail vehicle is embedded in the turbulent boundary layer sloughing at the rear, and there was little actual skin friction. Just turbulence all around.( some NACA airships were designed around this phenomena )
In Hoerner's section on trains and streamlined trains, I think some of the cars Cds WERE as low as the tail-car, but those tail-cars were fully boat-tailed, unlike the sedans and buses.

[JSH]

Daimler trucks tested automated convoys including 2 years of testing on public highways. What worked great on the test track failed on public roads. The fuel savings almost disappeared because human drivers would cut between the trucks and break the convoy. Then the following trucks would need to burn extra fuel to catch back up with the lead truck.

Somewhere out there is a video of a platoon of trucks doing synchronized auto braking based on the sensors on the lead truck.

[Bicycle Bob]

Originally Posted by JSH

Daimler trucks tested automated convoys including 2 years of testing on public highways. What worked great on the test track failed on public roads. The fuel savings almost disappeared because human drivers would cut between the trucks and break the convoy. Then the following trucks would need to burn extra fuel to catch back up with the lead truck.

Somewhere out there is a video of a platoon of trucks doing synchronized auto braking based on the sensors on the lead truck.

In my scheme, there would be no room for interlopers. The trucks would follow closer than railway cars.
One bit of wisdom from aircraft flying in formation - once you get really close, you just don't have room to build up much impact speed - if bumps happen, they usually don't do damage.