Hacker News Reader

Comment by tyrw | Hacker News Reader

I'd also add that virtually the only compelling reason to have a single, large load like a big rig is to minimize the cost of a human driver relative to payload shipped. Without a driver, the optimal load size will likely be much different and will vary more by industry than it does today.

View on HN

If anything, wouldn't the loads get larger.. since you could build trailers with more sensors, allowing more trailers to be attached to the same tractor... minimizing energy/fuel cost.

One tractor carrying larger loads is going to be more efficient than many small trucks with smaller loads: total weight over payload.

A human being can only safely handle so much cargo, and that's probably lower than could be automated.

The limit on truck size isn't because of human driving capacity, it's because road damage scales as the fourth power of axle weight. Trucks already do the vast majority of damage to our infrastructure, increasing the weight more would literally take down some older bridges.

I was referring to more trailers like this: http://www.hankstruckpictures.com/pix/trucks/macneil/2004/ma...

That doesn't require an increase in axle weight

I seem to recall hearing that some states have restrictions on trailer count. Presumably due to road safety issues.

Hmmm, I'm not sure the equation is so obvious.

If you don't have a driver, then the vehicle amounts to just a couple motors, batteries, and sensor arrays.

It doesn't make a difference if the battery is located in the front "truck" part of the convoy, or whether it's distributed throughout the trailers.

For a very long chain of trailers, you probably want a set of motors for every trailer right?

And as you've speculated, there's going to be a sensor array in every trailer.

So basically, you have motors in every trailer, batteries in every trailer, and sensors in every trailer. At that point ... why do you need a "truck" on the front and/or why are they connected at all?

Dropping a trailer vs waiting for it to be unloaded? I dunno. I agree with what your saying. Just moving stuff is obviously faster than waiting around for loading and unloading. At what point does the idle electric truck start to cost less than a simple trailer.

There's an "easy" solution to that too, you make it a flat bed electric self-driving trailer which takes a container similar to sea shipping containers on top.

Then you don't:

- have the unnecessary truck cab in front

- cost of the trailer being unused while loading / unloading

- potentially drastically change shipping containers received from over seas.

good point.. but that depends on the cost of the sensors, motors, etc. You could have a reduced set of sensors on the trailers, and more advanced set on the tractor.. and that may be cheaper than adding advanced sensors to every trailer.

Modular self propelled trailers are already a thing for moving heavy equipment they're just not for road use so most of HN will never see them.

You usually have a 100-500hp diesel running a big pump and hydraulic motors at the wheels.

Yes and no. Cost of fuel is also a big factor. A big rig is typically running about 6 MPG, and for lighter loads that doesn't change very much if you're hauling a half-size or full-size container. Sending two trucks means burning twice as much fuel, which could easily be hundreds of dollars.

But definitely that's less of a factor with an electric truck since the charging cost will be a lot lower than a comparable amount of fuel.

Cost of fuel will also be greatly reduced for the use cases within electric range:

- Removing the driver allows for more aerodynamic cab configuration, or no cab at all

- Electric motors are more efficient, particularly in high-torque / low-rpm environment

- Massive & inefficient 18-speed gearbox can be avoided

- Cost of fuel itself (electricity) is much cheaper

I think the bigger savings will come in being able to precisely control stops, starts, and turning, which will both minimize damage to the road surface and lengthen tire life.

ISTR a case where a large open pit mine bought GPS-driven trucks and saved a great deal just from longer tire life (each tire was $20K).

Re: gearbox, I wonder whether an autonomous truck could be paired with a little scouting drone to "look ahead" at things like blind corners or stop-and-go traffic, to allow the truck enough foreknowledge to gear up and down more gradually.

Reply on news.ycombinator.com