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Comment by TheJoeMan | Hacker News Reader

The technological innovation pace in large capacity batteries and motors for EV’s is very inspiring. However, everything has externalities that seem to be ignored or remembered only after the fact. The USA’s roads have a score of D <1>. These electric trucks are tremendously heavy, and road wear is proportional to vehicle weight to the 4th power! <2>. A possible future innovation might be reinventing the highway pavement system, either materials or methodology of resurfacing.

<1> https://infrastructurereportcard.org/cat-item/roads-infrastr...

<2> https://www.insidescience.org/news/how-much-damage-do-heavy-...

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No, road wear is proportional to the weight on each axle to the 4th power. More axles (like this tandem-trailer truck) can distribute the weight.

Of course that means more wheels needed, so more tires and other components. Tire wear also scales with axle weight (among other factors).

Total environmental impact depends on more than just the weight. The added weight isn't good, but may be offset by the other design changes.

So what's the downside to more tires?

https://www.washington.edu/news/2020/12/03/tire-related-chem...

EVs' heavier weight also cause more tire wear, creating more fine dust...

Is that based on the EV's overall weight, or is it proportional to the amount (or maybe contact area) of the tires?

The world is burning and you’re acting like dust matters. I’m so tired of this shit.

They aren't really that much more heavy than normal trucks. We're talking a couple of percent of the useful payload here. They aren't 'tremendously' heavy but just about the same weight give or take a couple of percent. A couple of tonnes of battery goes a long way. And it's not like big diesel engines, assorted plumbing and other systems, and a couple of hundred of gallons of fuel weigh nothing.

There's no need for new pavements, or any other solutions for a perceived problem that simply does not exist.

This vehicle has 10 axles, so it should put less wear on the road than a typical truck&trailer with 5 axles with a capacity of 45-55 tonnes of cargo. Wear is directly proportional to the number of axles.

But more tires, more tire wear, more micro-plastic pollution from the tire wear, etc.

Nope. Twice the number of tires means half the weight per tire. Half the weight means 1/16 of the wear per tire. Twice the number is 2X, so overall 1/8 the impact.

Any reason why we don’t put as many tires on (existing) trucks as possible? Seem like a good deal reducing tire wear.

It will complicate the control of the truck and add more components (increasing the cost).

Truck drivers don't have to pay for the negative externalities of tire wear

It would probably increase wear, not decrease it. When a vehicle with more than one non-steering axle turns, some of the tires must slide. It's mostly not too noticeable unless the corner is fairly tight or the trailer has at least three axles. You don't really want any more wheels on the ground than you need to support the load. Or you need to allow those axles to pivot.

Heck, even with my modest two-axle travel trailer I leave tire marks on my driveway where I have to turn sharply to get it onto the road.

Increased friction -> uses more gas/energy. Complicated the mechanical design; more moving parts you have to maintain in a more crowded area.

I think we need to look at it as a throughput question. How do we transport X tonnage from pt A to pt B? What’s more efficient? One truck with more axles or two separate trucks, with fewer, for example; taking into consideration roadwear, tire wear, bridge capacity, etc.

Fewer vessels for fewer total trips is the more efficient option as a rule. See: cargo trains and gigantic container ships. Australia has some super long cargo trucks they allow called road-trains, I think, which are justifiable if you can fit them onto roads.

The thing that needs to be balanced in the case of # of axles is the cost of outfitting each truck with additional axles and associated suspension/braking hardware versus the savings in tire costs due to reduced wear on the larger number of tires.

I wanted to add that there are a bunch of factors at play in this optimization problem that might not be obvious. For example, there are diminishing returns in reduced wear from distributing load over more tires at some point. More tires & rolling parts also tend to increase rolling resistance, even ignoring extra weight that tends to come with a more complex design. Another potential advantage of having more axles is to reduce the frontal area of the vehicle by arranging tires in the direction of travel instead of putting them side by side on the same axle. Frontal area is a big component of the drag on a vehicle, along with speed and drag coefficient.

Probably a train. Doesn’t even need to carry its own electricity source.

> reinventing the highway pavement system

A number of years ago there was a demo of a technology where they mixed (something like) iron filings in the asphalt. By slowly driving over it with a massive electromagnet they could heat the asphalt from within, helping to fix any small cracks before water ingress could cause a larger problem.

I've been pretty frustrated with the slow adoption of EV and PHEVs for large trucks.

EV drivetrains are so much better suited to heavy trucks for everything but range (thus... the hybrid). The insane torque they can deliver, the energy recovery in braking, simply is a revolution for them. The Tesla demo showed that being barely able to go up a mountain is a thing of the past with an EV drivetrain.

I had to drive an RV with a friend over the Appalachans, and then the constant undulating foothills of the eastern midwest. What is especially annoying is the automatic transmission can't handle the climbs without careful metering of torque by the driver, otherwise it does a loud and jerky downshift. EV drivetrains would have none of that.

The range? Put a generator onboard. For RVs they already have one in most cases.

The stability of the entire system would be enhanced with floor batteries. interior and storage space would improve. You have a huge room for solar cells, and for RVs, the roll-out sunshade could be further solar cell real estate.

The weight issue will improve with density. Sulfur, solid state, and semi-solid state are in the wings. But again, a hybrid drivetrain would reduce the amount of batteries needed and improve range.

We should have mandated the development of hybrid drivetrains in all wheeled transport two decades ago, which is five years after the Insight and Prius hit the market.

> The range? Put a generator onboard

A small trailer with a genset and extra luggage space would be enough to convert an compact electric car into a touring car. Even better if you could rent one only when you need it.

> The idea is that HCT will contribute to [...] reduced road wear [...]. One example is Finland, where it is permitted to drive with 76 tonnes of total weight and 34,5m truck combinations on most roads. Another is Sweden, where it is allowed to drive 74 tonnes...

Apparently it can actually reduce road wear, likely due to using fewer trucks (and therefore fewer axles), despite the absolutely massive size of the semi featured in TFA.

Considering how close the truck matches the length and weight limits of the road networks listed, I strongly suspect it was explicitely designed around said limits. Possibly coupled with a margin for safety and human inaccuracy at the weigh scale, or simply lowest common denominator for limits in a market not listed.

>A possible future innovation might be reinventing the highway pavement system, either materials or methodology of resurfacing

Yes. Perhaps we could replace tarmac and tyres with steel.

Obviously there would be grip implications, so we could cut grooves in the road, and add flanges to the wheels.

And the strength of guard rail needed to keep the vehicle in its lane is also proportional to .. the square of the weight (kinetic energy) if I could guess?

The size of the fire from one of these trucks getting into an accident is going to be impressive

Yes, it would almost be like the fires you have today, when a truck explodes that's carrying fuel for all the other fuel using vehicles.

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