P=mv

7 Dec, 2020

Speed is one of two factors in car crashes. The other factor is mass.

We know this from classical kinematics, where we have the concept of 'P=mv'. P means momentum, & can be measured using bizarre units such as 'meters * kilograms per second'; but intuitively we can say that momentum is the product of speed times weight, so every bad crash is the product of 'a fast/heavy thing slamming into somebody'.

Where I live, every road has 'speed limits'. Outside my apartment you aren't supposed to go faster than 50 km/h, although obviously people do. & they go that fast in extremely heavy cars: up to 2500 kilograms, or something wild like that.

We do have 'weight classes' for automobiles, & we've got special little licensing programs that regulate when 'a car' crosses over into being 'a light duty truck'. Yet the weight limits are pretty absurdly generous, so basically any standard car-driving person in my city gets to choose for themselves whether they want a high-momentum car (say an SUV) or a low-momentum car (a little hatchback-type thing).

"Which one of those cars should I pick?" is an extremely complicated question that strikes all the way into the heart of what 'being a driver' really is. Driving is a privilege, practiced by millions of humans daily; their collective values/habits create 'cultures of driving' that will over-determine most answers to questions like 'which car?'

If your little town has only small hatchbacks, it makes perfect sense for you to drive a small hatchback. But what if your neighbors are all rich assholes, who buy the largest SUVs they can afford just because? (In game theory we'd call the presence of these assholes "a Nash Equilibrium".)

In a driving culture that mixes hatchbacks with SUVs, the heavier-and-taller SUV will provide additional layers of privilege over-and-above the hatchback. This is simply because the SUV will crush any hatchback it hits, potentially killing those passengers (yet protecting the ones inside the SUV).

Here we can observe a certain powerful incentive for rich assholes to buy SUVs (reasoning, the way rich assholes always do, that their own family should be allowed to kill other families because it's just worth a little bit more). My government unfortunately supports the rich assholes in their reasoning; its official weight ratings judge heavy-ass rich-people cars 'equal' to the lighter cars, & that assumed equality creates a classic Prisoner's Dilemma:

Capitalists love this kind of dilemma because they know at least one rich asshole is gonna take the SUV, & this will then trigger a wave of rich assholes doing predictable 'rich asshole'-type behaviour. All will buy SUVs; some will even get duped into buying a hatchback THEN an SUV. Nobody will wind up safer (aside from a class-level safety bonus held above pedestrians and/or those who struggle to afford cars).

Of course my city's mayor & council & planners all pay exhausting lip service to 'pedestrian-oriented realms'; of course they pretend to be fighting climate change by reducing car use 0.00001% in whatever trivial way they came up with this month. Of course they would tell me that NO asshole family has de facto permission to murder other families. But these things they tell me are all lies, & it's pretty easy to see how they're lies.

I submit to you as evidence the simple law of P=mv, & the fact that every driver around here treats it far more seriously than anything we wrote in our bylaws. You can see this literally anywhere you look.

Like last week there was some construction equipment parked along the road, & they'd draped a scrap of caution tape half-assedly around one part of it (to uh... make sure people used caution, I guess).

Why, do you think, was the boss guy satisfied that some half-assed safety tape could protect his fancy equipment from dangerous drivers? Well, it's because safety tape was never necessary to begin with. Boss guy's equipment was already protected, by weighing four times more than a pickup truck. The disincentive for hitting it is that the resulting change in momentum would kill you.

Drivers know this on some kind of animal level, so owing to the shrewdness of our animal brains we can conclude something like: "Heavy construction equipment protects ITSELF from asshole rich people!"

(While we must conversely conclude that pedestrians can't be protected from asshole rich people at all, save by removing cars from public spaces.)

Another really obvious example of P=mv is the way drivers act around crosswalks. Last year I was nearly killed by a van in the middle of an active signalized crosswalk. The blinking white stickfigure and painted roadlines said I, the pedestrian, had 'right of way'; so why'd the van accelerate over the painted lines & miss me by less than 1 meter?

Well, the van was executing a left turn through this crosswalk, so the guy in the van had his eyes glued to the right side of the cross-street (where maybe there would be a rich asshole in an SUV speeding along). He knew, instinctively, the law of P=mv: That his van would crush any pedestrian he encountered like a bug, that the insurance company would declare my death legal, & that ultimately the consequences for pedestrian slaughter would remain minimal (pedestrians simply don't have enough mass).

Van driver knew the same thing my government knows, & which I think my government actually taught him: To worry endlessly about the potential for cars, but never worry at all about pedestrians, because P=mv.

My city's wealthiest residents all like to imagine themselves as "good neighbors", which requires imagining themselves as "good drivers". Of course on a surface level they believe things like "I never run through crosswalks!" and "I value human lives!"

Below the surface though, they're just like any other car operator: They have good days & bad days. Some days they'll live up to their respectable self-image. Other days they'll plow through crosswalks shouting obscenities after the people they almost struck. ("STOP WEARING BLACK HOODIES WHILE MY CAR IS ON THE ROAD!")

Never in these people's lives will they choose to settle for a dinky hatchback (or god forbid, a non-luxury transport mode). Never will they exercise bravery by avoiding some pedestrian at extra risk to themselves (missing the person in order to hit nearby construction equipment). Never will they actually become the good neighbor they imagine, because they know as well as everybody that P=mv. Their lives are all about maintaining the momentum they've accumulated: getting more massive, gaining more speed, attaching more & more reckless power to every little movement they make. They view themselves as free & independent particles, zipping through life towards their own benign objectives (occasionally ramming into smaller particles & 'accidentally' crushing them).

Folks in this city treat 'acquiring more leg room' to be the core aspect of dignified life (even if most ppl won't ever get to do that). They crush their human/animal peers on a daily basis, little by little in a hundred different ways (as hatchbacks become SUVs become smoky summer skies). 'Sacrifice' is just something for other organisms to get stuck doing (the ones who didn't invest enough in 1980s real estate, or whatever).

Now that Earth's climate is collapsing, the logic around P=mv has started shifting rapidly. 'Twas fossil fuels that allowed for the automobile to begin with, enshrining today's detachment between 'weight' and 'speed' (such that no matter how heavy something got, it still went 50km/hr + somehow permited next year's model to contain 'even more legroom!'). Fossil fuel infrastructure will disappear soon. What's going to happen then is that P=mv starts flipping back to its pre-industrial orientation (a world in which 2.5 tonne death tanks were considered rather pointless to construct).

As we exit gradually from our disgusting 'magical dino juice!' view towards fossil fuels—wherein the burning toxic nightmare shit was somehow supposed to grant 'cheap death tanks!' forever—we must likewise move away from industrial-era concerns. We don't so much care where to legally cap the speed of our flying nightmare-shit death tank; instead we have the more basic question of 'how do I take my body + this motionless pile of goods and cause them to start moving in a direction!?'

The short answer to this question is: you use a bicycle. The long answer is, you get very serious about reduced weight/increased energy efficiency, then you remove as many not-strictly-necessary design features as you possibly can, and eventually the resultant transport vehicle/human settlement pattern looks 95% like trains, buses & bicycles.

Car drivers seem genuinely horrified by this, & I feel I understand their horror on a deeper level than they do.

Sure, the surface thing they say is just some tedious bullshit re: 'obeying the rules'. They tell big stories re: how 90% of cyclists ignore stop signs; or they worry quite loudly & publicly re: any possible privilege a cyclist might receive over/above what you get as an SUV-driving rich person. They build big rhetorical Jenga towers concerning how 'actually cyclists are the REAL hyper-luxury gentrifying rich-person's tool!' & they'll often have some weird idea in their back pocket that automobiles are fundamentally proletarian. (To be honest I do not see how 'generating climate change to benefit rich guys' could really be proletarian—I think we basically all got scammed by these car companies, & it's as simple as that—but you need to check the Jenga tower if you really wanna know the line of reasoning.)

A much more helpful tool for analyzing cyclist/driver behaviour is to consider how P=mv. Drivers are used to imagining their 2500 kilogram death tank as 'politically equal' to a hatchback, or a cyclist, or an 85 kilogram jogger who happens to be crossing the street right this second. I believe that in the heat of the moment—were some crash to take place that threatened their lives—the drivers would acknowledge how unequal these particles really are (& like van guy, they'd choose to dodge potential autos in favor of plowing through potential joggers). For the purposes of posting rhetoric on Facebook however, everybody maintains our government's bullshit sense of 'equality'; they basically act as if every person & vehicle should pretend they're an SUV (because this is one surefire method to maximize the benefits of owning SUVs).

Rigidly-observed stop sign adherence is important to industrial-era British colonists, because it results from people piloting death tanks at velocities that are way too fast. Whenever death tanks ignore stop signs, the predictable result is death (because the the death tank's pilot has no reasonable ability whatsoever to sense what's in that cross-street prior to hurdling through it).

On a 13 kilogram bike, however, the whole situation becomes really a lot different. Bicycles are too light to justify air bags/bumpers/rollcages etc, so the range of 'traffic manoeuvres that could easily kill the pilot' is larger than it ever was for drivers. The speed of bicycles therefore tends to be real slow (could be like 20km/h!), & their stopping distance tends to be real short (could be like 2 meters!), & there's even a good chance their ears can tell whether any death tanks are roving around nearby.

Of course I feel cyclists should still respect traffic laws; of course I find it stressful to watch people prioritizing P=mv over our government's 'official rules of the road' (since it could lead to confusion/mistakes). Yet I watch drivers do this same unsafe shit hundreds of times every single day, & the main difference is that their class of particle weighs 2500 kilograms while the other weighs maybe 100. That's a difference of 25x. The car is 25 times deadlier.

I can think of few better metaphors for privilege in our society than 'the mass somebody carries while being personally transported'. Like privilege, mass is politically-concealed: Our leaders view the bicycle, hatchback and 2.5-tonne death tank as simply 'vehicles that must travel the speed limit' (unless drivers are rich or connected) & so it's no surprise how all the comfort/luxury in transport came to rest within these useless fucking machines.

Our leaders never cared which vehicles cause climate change; they never cared about crashes, & will always dance away from simply acknowledging that P=mv. Nobody in my government has ever been forced to reckon with the fact that 'increased legroom!' translates directly into increased human corpses. This, in a nutshell, is why capitalism keeps winning.