Musk’s possible reasoning… from the patently absurd to the practical:
The problem: road wear is dependent on overall usage and vehicle mass*. Damage per vehicle-mile-travelled is linear. Damage per vehicle mass is not:
Vehicle usage is hopefully self explanatory. Annual vehicle miles traveled (VMT) in the US have increased from 1.5 trillion in 1980 up to 3.1 trillion in 2021. Total miles of highways are also increased in that time by about 10%.
Vehicle efficiency is related to engine size and overall vehicle mass (generally, amongst sundry other factors).
Average vehicle mass increased by a third since the 80s, up to 4,400 lbs in 2023 in the US, vs 3,200 lbs from 1980-1987.
Average vehicle efficiency increased about 30% from about 21 mpg during the 80s up to 27 mpg in 2023.
Explore the Automotive Trends Data | US EPA
So what conclusions can we make? We’re driving more miles and doing more damage per mile and using less fuel to do it, which is both increasing the expense associated with road maintenance while diminishing the (primary?) revenue source to pay for it.
What other options might there be?
I’m done nerding out for a mental break from the day - what else might the commentariat suggest doing?
*And yes, studded snow tires in some winter states.
The prototypes will need to be delivered by 2028, with the other four arriving by the time the Merced-to-Bakersfield segment nears operation. All trainsets will need to be tested to reach speeds of up to 242 mph, the Authority said.
That might be oversimplifying things when it comes to EVs. Compared to similar vehicles, EVs have lower center-of-gravity due to the common design of putting the batteries low in the vehicle. Road wear would be significantly less for a vehicle with lower CoG than the same mass vehicle. All the hand-wringing about EV mass may be for a nonissue.
I am struggling to understand why that would be.
Yeah, that math does not check out to my engineer-brain either. Center of gravity affects handling and driving feel, sure, but it’s the same downward force due to total mass whether it’s high up or low down in the vehicle volume.
Okay, okay. Bicycles are not vehicles with engines. But I found the collection of photos of war bikes interesting.
Concrete is strongest in compression, ok in shear, and weak in tension. The static mass of a vehicle doesn’t wear concrete. Shear does. So braking and turning forces are what cause road wear (along with extraneous factors like erosion and foreign objects like loose rocks and metal debris).
A lower CoG reduces the lever arm the moving mass of a vehicle applies to the road. Essentially, anything that causes tire wear causes road wear, as they are opposite sides of the same coin. Vehicles with lower CoG have less tire wear. They also cause less road wear for a given set of tires.
ETA: digging a bit deeper, it appears the vehicles aren’t even the primary cause of road wear. In cold climates, freeze/thaw cycles are. For concrete, water erosion is also higher up the list. Finally, for asphalt roads, petroleum residue causes degradation of the substrate and accelerated wear.
ETA2: Here’s a quote from a civil engineer in charge of road design and construction in the UK: “Shear flow represents more damaging (than compression) form of rutting (in asphalt). It is commonly seen at traffic lights and bus stops.”
Hot take… acceleration, such as from a stop, would induce shear. I’m told electric motors can generate a lotta torque on a dime…
Sure. I think “don’t drive like a dick” is independent from the fuel source, though.
Yet we keep putting heavier, more powerful vehicles in the hands of dicks… “dick-hands drivers ” if you will.
