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> I suspect bike collisions are more common than car collisions You do? I was thinking the opposite: I've never hit anybody on my bike, I've never been hit by

> I suspect bike collisions are more common than car collisions You do? I was thinking the opposite: I've never hit anybody on my bike, I've never been hit by a bike, I've never seen nor heard of anybody being hit by a bike. How about you? I have absolutely hit a few cars, though. I figure that since you have to pay attention when cycling, otherwise you end on the ground, and speeds are relatively low, you're never really in danger of hitting someone. I had a close calls with a kid literally jumping out of a bush once, but that's it. Obviously, I'm not cycling on sidewalks, so in cities with crappy infrastructure, maybe it's more likely. Vis-a-vis the chance of injury: I think car bonnets have generally got higher in the last few years, but I think the main question is the weight. If you get hit by a bike, both you and the bike are going to bounce. If you get hit by a car, you're going to be doing basically all the bouncing. The energy of an impact is F = mv/2t. So mass is just as relevant as velocity. Regardless, the statistics bear this out: your stats showed that even if there were as few cars as there are bikes, they would still kill an order of magnitude more people. Perhaps this is because cars are much faster, perhaps this is because they hit more people, or injure them more when they do so, but I think in general if you're taking a purely objective, statistical view, every person who leaves their car in the garage and takes the bike instead makes everybody safer.

everforward 3y ago
> You do? I was thinking the opposite: I've never hit anybody on my bike, I've never been hit by a bike, I've never seen nor heard of anybody being hit by a bike. How about you? I have absolutely hit a few cars, though. You would have to weight that by usage, though. There are dramatically fewer cyclists; especially if you weight it by distance travelled. I've been in dozens of bicycle accidents, they just primarily consist of me being young and bad at riding on a bike, or hitting a curb wrong, or taking a hard turn with muddy tires a couple of times. They just don't rise to the point where they stick out in my memory. > The energy of an impact is F = mv/2t. So mass is just as relevant as velocity. That formula measures the kinetic energy of an object, not the energy imparted by an impact. Just as a stupid example, a 2,000kg car moving at 100m/s has the same kinetic energy as a 2,000,000kg ball moving at 0.1m/s. The outcome of getting hit by those objects is completely different though. > If you get hit by a bike, both you and the bike are going to bounce. If you get hit by a car, you're going to be doing basically all the bouncing. Sure, I agree with this, but disagree with the conclusion. From a physics perspective, what you're saying is that someone who gets hit by a bike is absorbing all of the kinetic energy of the bike, where someone who gets hit by a car is only absorbing a fraction of the car's kinetic energy. > I think car bonnets have generally got higher in the last few years, but I think the main question is the weight. I still think you're under-weighting those bonnets, the bonnets getting higher is a big issue for pedestrians. Think about the direction of the force as those bonnets get higher. Low bonnets push below your center of gravity and center of mass; they don't have the angle to impart velocity to most of your mass. High bonnets can impact directly with your center of mass, which will most definitely impart velocity. https://sklc-tinymce-2021.s3.amazonaws.com/comp/2022/03/Head%20Impact_1647577514.gif https://sklc-tinymce-2021.s3.amazonaws.com/comp/2022/03/Head... that's a pretty decent diagram of what a relatively low-speed impact with a low-bonnet car looks like. As long as the person is reasonably healthy and doesn't crush their skull when it hits the hood, their odds of surviving are good. At some velocity, that impact with the windshield does become energetic enough to be a big problem (like immediate death, or being flung a dangerous vertical distance). When that bonnet gets high enough, rather than pushing the pedestrian into a sitting position and then over the top of the car, it collides with their stomach/chest and they either get mashed into the grill and eat the full energy of that collision, or they get pushed under the chassis into the wheels. So the relevant question becomes whether that fraction of the car's kinetic energy is greater than or less than the bike's total kinetic energy. It's probably really more about acceleration, but that should roughly align with the kinetic energy. > Regardless, the statistics bear this out: your stats showed that even if there were as few cars as there are bikes, they would still kill an order of magnitude more people. Perhaps this is because cars are much faster, perhaps this is because they hit more people, or injure them more when they do so, but I think in general if you're taking a purely objective, statistical view, every person who leaves their car in the garage and takes the bike instead makes everybody safer. I wouldn't even try to venture a guess at that aggregate. I would guess bikes are probably less likely to kill people, but there's a ton of confounding variables like how long-range travel is handled, whether the density of riders affects safety like it does with cars, etc. It's hard to make direct comparisons anyways because of usage limitations. I suspect cars would be enormously safe if we limited them to operating at bicycle speeds. The quick stats I could find say that in a vehicle-pedestrian collision at 20mph, there's only a 2.5% chance of fatal injuries for the pedestrian. That jumps to 20% at 30mph. At 10mph, it's well under 1%. Motorcycles are basically bikes that operate in the same realm as cars, and they have a very poor safety record for everyone involved.
- pasabagi 3y ago
  I have come off my bike a whole lot of times, but they've always either been I've been doing something stupid, or the street design is stupid (there's a spot in my city where you can sit and watch cyclist after cyclist eat shit when they hit a particular bunch of tramlines). In general, I think anything can be made safe if you make appropriate design decisions: consider nuclear reactors. Unfortunately, we live in an era where urban planning is generally neglected as a discipline, so states tend to try and push safety onto the street-users, which is often pretty silly: no amount of high-vis gear and protective equipment is going to make sharing a road with 60mph cars safe. You can't stop drivers from driving drunk by just shouting at them: you actually have to plan cities so you can get home from a bar without using your car. You can't stop cyclists from riding on the sidewalks without providing cycle lanes, and so on. The thing that boils my blood a bit is that the car industry has lobbyists, while cyclists do not, so often planning law is massively in the favour of cars. For example, in Germany, you need multiple cyclist fatalities before the city is even allowed to build a bike way[0]. [0]: https://www.gesetze-im-internet.de/stvo_2013/__45.html https://www.gesetze-im-internet.de/stvo_2013/__45.html --- basically, the city is only allowed to cordon off a bit of the street for 'specific' uses when there's a proven danger. So the road is, in the eyes of the law, 'generally used', even if in practice only cars can actually safely use it, and the city is not even allowed to put in a bike lane unless in the normal course of events you get like a bunch of cyclists being mulched.

everforward 3y ago

> You do? I was thinking the opposite: I've never hit anybody on my bike, I've never been hit by a bike, I've never seen nor heard of anybody being hit by a bike. How about you? I have absolutely hit a few cars, though. You would have to weight that by usage, though. There are dramatically fewer cyclists; especially if you weight it by distance travelled. I've been in dozens of bicycle accidents, they just primarily consist of me being young and bad at riding on a bike, or hitting a curb wrong, or taking a hard turn with muddy tires a couple of times. They just don't rise to the point where they stick out in my memory. > The energy of an impact is F = mv/2t. So mass is just as relevant as velocity. That formula measures the kinetic energy of an object, not the energy imparted by an impact. Just as a stupid example, a 2,000kg car moving at 100m/s has the same kinetic energy as a 2,000,000kg ball moving at 0.1m/s. The outcome of getting hit by those objects is completely different though. > If you get hit by a bike, both you and the bike are going to bounce. If you get hit by a car, you're going to be doing basically all the bouncing. Sure, I agree with this, but disagree with the conclusion. From a physics perspective, what you're saying is that someone who gets hit by a bike is absorbing all of the kinetic energy of the bike, where someone who gets hit by a car is only absorbing a fraction of the car's kinetic energy. > I think car bonnets have generally got higher in the last few years, but I think the main question is the weight. I still think you're under-weighting those bonnets, the bonnets getting higher is a big issue for pedestrians. Think about the direction of the force as those bonnets get higher. Low bonnets push below your center of gravity and center of mass; they don't have the angle to impart velocity to most of your mass. High bonnets can impact directly with your center of mass, which will most definitely impart velocity. https://sklc-tinymce-2021.s3.amazonaws.com/comp/2022/03/Head%20Impact_1647577514.gif https://sklc-tinymce-2021.s3.amazonaws.com/comp/2022/03/Head... that's a pretty decent diagram of what a relatively low-speed impact with a low-bonnet car looks like. As long as the person is reasonably healthy and doesn't crush their skull when it hits the hood, their odds of surviving are good. At some velocity, that impact with the windshield does become energetic enough to be a big problem (like immediate death, or being flung a dangerous vertical distance). When that bonnet gets high enough, rather than pushing the pedestrian into a sitting position and then over the top of the car, it collides with their stomach/chest and they either get mashed into the grill and eat the full energy of that collision, or they get pushed under the chassis into the wheels. So the relevant question becomes whether that fraction of the car's kinetic energy is greater than or less than the bike's total kinetic energy. It's probably really more about acceleration, but that should roughly align with the kinetic energy. > Regardless, the statistics bear this out: your stats showed that even if there were as few cars as there are bikes, they would still kill an order of magnitude more people. Perhaps this is because cars are much faster, perhaps this is because they hit more people, or injure them more when they do so, but I think in general if you're taking a purely objective, statistical view, every person who leaves their car in the garage and takes the bike instead makes everybody safer. I wouldn't even try to venture a guess at that aggregate. I would guess bikes are probably less likely to kill people, but there's a ton of confounding variables like how long-range travel is handled, whether the density of riders affects safety like it does with cars, etc. It's hard to make direct comparisons anyways because of usage limitations. I suspect cars would be enormously safe if we limited them to operating at bicycle speeds. The quick stats I could find say that in a vehicle-pedestrian collision at 20mph, there's only a 2.5% chance of fatal injuries for the pedestrian. That jumps to 20% at 30mph. At 10mph, it's well under 1%. Motorcycles are basically bikes that operate in the same realm as cars, and they have a very poor safety record for everyone involved.

pasabagi 3y ago
I have come off my bike a whole lot of times, but they've always either been I've been doing something stupid, or the street design is stupid (there's a spot in my city where you can sit and watch cyclist after cyclist eat shit when they hit a particular bunch of tramlines). In general, I think anything can be made safe if you make appropriate design decisions: consider nuclear reactors. Unfortunately, we live in an era where urban planning is generally neglected as a discipline, so states tend to try and push safety onto the street-users, which is often pretty silly: no amount of high-vis gear and protective equipment is going to make sharing a road with 60mph cars safe. You can't stop drivers from driving drunk by just shouting at them: you actually have to plan cities so you can get home from a bar without using your car. You can't stop cyclists from riding on the sidewalks without providing cycle lanes, and so on. The thing that boils my blood a bit is that the car industry has lobbyists, while cyclists do not, so often planning law is massively in the favour of cars. For example, in Germany, you need multiple cyclist fatalities before the city is even allowed to build a bike way[0]. [0]: https://www.gesetze-im-internet.de/stvo_2013/__45.html https://www.gesetze-im-internet.de/stvo_2013/__45.html --- basically, the city is only allowed to cordon off a bit of the street for 'specific' uses when there's a proven danger. So the road is, in the eyes of the law, 'generally used', even if in practice only cars can actually safely use it, and the city is not even allowed to put in a bike lane unless in the normal course of events you get like a bunch of cyclists being mulched.