Fuck Cars
A place to discuss problems of car centric infrastructure or how it hurts us all. Let's explore the bad world of Cars!
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This needs to be updated.
Getting hit by a pickup truck at 30 MPH is similar to getting hit by a Honda Civic at 120 MPH for kinetic energy.
That's besides the fact that pickups have a much taller hood vs sedans so there are significantly higher rates of head/internal injury.
Taller cars and trucks are more dangerous for pedestrians, according to crash data
https://www.chicago.gov/city/en/sites/complete-streets-chicago/home/traffic-safety/vehicle-size-and-speed.html
I got hit by a large SUV doing between 30mph and 40mph a few years ago. I can’t tell you why or how, but I had a split second to twist and plant my hands on the hood and jump so I went up instead of under. Went into the windshield (broke it) and then got launched when she slammed on the brakes. It put my radius and ulna into my hands, my back into my guts, and knocked my brain so hard I gave the emergency crew a phone number that belonged to a girlfriend I’d broken up with almost 20yrs prior. Took me a year to be able to write again, not just physically. I’d start putting words to paper and end up with gibberish because between my brain and my hand it didn’t connect. Had to leave post-it notes around the house as a check list- did you eat, bathe, brush your teeth, feed the dogs, piss? My ability to sleep was wrecked, no circadian rythym. I don’t entirely believe in fate, but how the fuck that didn’t kill or cripple me boggles my mind (what’s left of it) daily.
That's horrible. I can't imagine going through that.
Glad you're alive. Thank you for sharing.
You'd have to be very unlucky to get hit ffrom both side at the same time though
We wouldn't have so much trouble with this if all men had the same size dick.
Let's not bring body shaming into this mmkay?
Its not body shaming, its overcompensation shaming.
They'd just lie about it anyway
Your math is wrong. Kinetic energy scales linearly with mass, quadratically with speed. The graphic you included supports the idea that at same speed, the pickup truck has double the KE. The 120 mph sedan has dramatically more KE than a 30 mph pickup.
Assuming that your sedan has exactly half the mass of the pickup, it would match a 30 mph pickup's KE at 30*sqrt(2) mph, which is somewhere between 40 and 45 mph.
There's quite a large discrepancy between this image and OPs image. This image says the survival rate of 30 mph (48 kph) is 60%, while OP's image says 50 kph it's at 20%. I wish they included a source for the data that could explain it.
This is the same issue I take with braking distance scales. They often vary wildly, and some don't even follow a quadratic increase in distance like you'd expect.
The energy difference is only really relevant if the thing you're hitting is significantly heavier or at least similarly heavy like a house or another car. For a person it's still much worse, but that is moreso because of the high hood of the car.
I know pickup trucks are heavy, but I'm surprised they are 16 times heavier than a Honda civic. The more you learn.
Well... the person in the last photo looks like they're not happy about getting hit by a moving vehicle at all.
If we're going for efficiency, I think getting hit by both cars is the right move.
I am not sure why the difference in energy related to vehicle mass is relevant here as humans have an insignificant amount of mass compared to either vehicle, so transferred energy should be roughly the same. However, the difference in how the collision plays out (pulled under Vs thrown above) should be a huge impact
The higher mass and force transmitted by a truck means the human will be thrown further and possible impact other objects at a higher speed
I think the point is that it's not a linear scale when comparing energy of the vehicle to energy transferred during impact. It flattens out drastically at higher vehicle masses, and the value of the energy becomes a false or skewed argument against heavier cars.
Not all of that energy is transferred. The car doesn't stop as if it hit a wall. Usually it barely slows down. The human on the other hand gains at most the kinetic energy corresponding to their body mass and the speed of a human bouncing forward off the car at around the same speed as the car was going, so a tiny fraction. Of course impact geometry will determine the specifics and pickups suck there too. The important thing about kinetic energy is that it's dependant on the square of the velocity. That's why speed kills. The mass is just a linear relation.
The issue is energy transfer doesn't care about weight of the human, more kinetic energy will impart more speed to the human during the impact impulse. Imagine a solid bowling ball hitting a beach ball vs a plastic hollow bowling ball hitting a beach ball
You are thinking of perfectly elastic collisions. That's a fantasy and not applicable to the real world. A human body isn't a beach ball and cars have crumple zones (although I believe pickups suck in this regard as well).
And your comparison isn't applicable in terms of masses either. Both a sedan and a pickup are way heavier than a person.
Edit: Without getting too deep into the math, let me put it this way: The energy of the impact is equal to the energy that the car loses during that impact. The car doesn't lose mass, so it depends instead on how much the car loses velocity. That depends on how the mass of the other object stacks up against the mass of the vehicle. Car hits something much heavier than itself? It stops and all of it's kinetic energy is expended. Car hits something much lighter? A bug on a windshield. A human obviously isn't quite as neglibly light as a bug and the mass of both the human and the vehicle do factor into this, but with both a sedan and a pickup truck, the speeding vehicle never expends more than a fraction of it's kinetic energy on the impact itself. The rest of it is dealt with via breaking, and a pickup will have a harder time slowing down due to it's kinetic energy.
Car crumple zones are tuned to prevent damage to the car, not to pedestrians. If they were they would have airbags on the front of the car. A car can kill a pedestrian by hitting them with a crumple zone, without that zone crumpling.
This means most of the non-elasticity is in the pedestrian's body; how they flop onto the hood of a normal car, and how their bones crumple and flesh splatters before their brain and vital organs do.
Of course if a car hits a pedestrian hard enough, the crumple zone will crumple to reduce damage to the car, but that's overkill as far as the pedestrian's life is concerned.
That said, if you (unrealistically) assume the speed at impact and the geometry of the hood are the same, the difference between a car that weighs 20 times what a person does and one that weighs 40 times that is (40/41 - 20/21), or only about 2.5%.
Realistically, the weight increases the braking distance and the hood geometry makes the pedestrian's body perish more elastically.
Well, yeah. I can kick a dent into a car, but mostly I just raised crumple zones to emphasize that these are inelastic collisions we're talking about.
And yes, the breaking distance is pretty much the only way that vehicle mass is relevant for pedestrian survival.
Partially correct, the speed (technically acceleration) of the human after a collision is limited by the decceleration of the moving object caused by thr human. Since a car and a truck decellerate about the same amount when receiving the counter-acceleration of the human, the force transfer remains similar.
The bowling ball will not slow down in the slightest when is hits the beach ball, accelerating the beach ball up to it's speed.
The plastic ball will lose significant speed hitting the beach ball, decelerating itself significantly as it accelerates the beach ball.
I'm going to pick some easy math speeds/masses for demonstration. 2,000 kg sedan, 4,000 kg pickup and 100 kg human. Starting velocities of 20m/s and 0m/s. An impact/acceleration time of 1s.
The sedan hits a pedestrian with (f=ma) of 40kN. It takes 2kN to bring the human up to 20 m/s. So the sedan will be somewhere around 38kN, or 19m/s at the end of it and the human absorbing 1.8-2kN.
The truck has f=80kN. Same 2kN for the human. So the truck will be somewhere around 78kN or 19.5m/s at the end. With the human absorbing 1.9-2kN
In either case the we talking a difference of 1.8-2kN for the human. Regardless the mass (and total force) of the vehicle, the relatively small human as a maximum force they can absorb. And that maximum force is heavily related to the speed of the larger object.
Not to say trucks/SUVs aren't deadly for other reasons (like where and how the force os transferred)
So my curved front sports car is totally safe to ram into pedestrians with?
/S
I'd rather be hit by that at 20 MPH instead of a full duty lifted pickup with a fresh shiny paint job on chrome wheels (mall crawlers)
I don't think pickup trucks should be banned. They should be commercial use only. It's not a family car or a daily driver.
Fuck mall crawlers
And then there is the SUV class. Aka the non-passenger work vehicle family passenger vehicle.
So they passed laws for emissions and fuel efficiency of passenger vehicles to help with pollution.
These laws force MPG ratings on sedans and SUVs. But they're looser for trucks. Car manufacturers realized its also looser since its calculated by weight.
So these fuckers decide to build SUVs on pickup truck frames and make pickups even bigger so they don't have to tighten up the fuel efficiency...
This is one of the main reasons there are so many bigger class vehicles being made now.
Add in all the new LED headlights. Which are too bright because the regulations are outdated based on wattage instead of lumens.
So you have taller vehicles with brighter headlights blinding everyone.
I'm at the point where I'm aiming for a SUV instead of a sedan for my next car...
If you dudes want to start over, feel free to copy our regulations. It would also allow you to sell cars here. LED headlights are great, given they keep to regulations.
Best, an European.
K = 1/2/*m/*v^2