Though at the mass ratios of car vs pedestrian/cyclists, the difference on the car side makes no significant effect. It doesn‘t really matter if the ratio is 1:10 in favor of the car or 1:20. The acceleration that the car will feel is negligible either way.
The obvious difference is that a human on a bicycle is moving on the order of 10 times less mass than a human in a car. Like my sibling post notes, it could be different for, e.g, a motorcycle, but a cyclist also produces about 0% of the SOx, NOx, or particulate emmissions of those vehicles, whichever is a somewhat different conversation.
Ahh the old “let’s apply rules designed for cars to bicycles” fallacy
Some of what you have said is correct but let’s make this clear: cycling across a pedestrian crossing at walking pace posses vastly less threat to human life than a car doing that would.
Fundamental physics, momentum=mv
Bicycle plus rider: 100kg
Car: 1500kg
That’s a 15x
For a comparison,
Human: 80kg
Bicycle + rider: 100kg
That’s 1.25x
If we assume that risk is proportional to momentum, then that’s an 125% increase of threat from a bicycle vs a human (running at the same speed) and 1500% increase of threat from a car vs a bicycle.
So to compare cars to bicycles doesn’t work, they pose a vastly reduced threat to human life va cars and in fact, cars pose more of a threat to cyclists than they do to pedestrians (I.e more cyclist die in car accidents that pedestrians).
It can make a difference in your braking distance and agility. Not specifically for pedestrians/cyclists, but that greater kinetic energy is a safety concern in higher speed collisions with other vehicles.
In a typical city scenario, a car has KE of 1/2 (2000 kg) (50 kph)^2 ~= 2e5 Joules. A bicyclist has 1/2 (100 kg) (30 kph)^2 ~= 3.5e3 Joules. Almost 100x less capable of inflicting damage on a typical pedestrian. Add onto this that bikes are way more maneuverable, less collision surface area, are totally exposed to the same forces exerted on the pedestrian with which they may collide... your comparison with cars is intellectually dishonest because you are comparing a human on top of a 10-20kg machine with a human inside a 2000kg metal box with an incredible array of safety features for the driver and hardly any for pedestrians outside.
Being hit by a car is invariably worse than hitting a car, because the car is carrying orders of magnitude more kinetic energy. It's simple classical mechanics - (1/2)mv^2. A car has 15-30x more mass and is travelling 2-4x faster than a cyclist.
If I'm filtering through slow traffic at 10mph and clip the side of a car, I'll have a minor tumble - scuffed handlebars, grazed palms, dented pride.
If a motorist clips me at 40mph, I'm almost certain to suffer serious injuries. I might be hit on the back of the head by a wing mirror, I might be dragged under the wheels, I might be launched over the hood, I might be bounced into some street furniture.
Are we actually going to compare the momentum of a bike in a vacuum? I will give you 20kg for a bike even, because the weight of the bike is so negligible.
100kg * 24km/h = 2400 kgkm/h
vs a car
If we cross-reference this with a list of pedestrian fatalities based on speed [1] Assuming a standard car size of 1000kg.
1000kg * 25kph = 25000 kgkm/h == 10% Risk of severe Injury
1000kg * 37kph = 37000 kgkm/h == 10% Fatality
1000kg * 51kph = 52000 kgkm/h == 25% Fatality
1000kg * 67kph = 67000 kgkm/h == 50% Fatality
1000kg * 80kph = 80000 kgkm/h == 75% Fatality
1000kg * 93kph = 93000 kgkm/h == 90% Fatality
I'm not saying this doesn't happen, but you're looking at momentums that are an order of magnitude smaller than momentums where people are at severe risk of injury with a car. I will choose to get hit by the bicycle every day of the week.
It's not 0 risk; 12 pedestrians were killed by bicyclists in NYC in 2021 (I don't have more up to date data, there doesn't seem to be a ton out there). Cars killed 1,927 pedestrians in the same year.
If we make a bold assumption that we can just scale those numbers by volumes, cars would have killed 100 people in the same period of there were as few drivers as bikers.
I think cyclists underestimate the difference made by the force focusing effect of landing on a bar as opposed to the roof of a car, as well as that bicycles are basically flat in the front instead of sloped, so people can't slide over the top.
If I could pick between getting hit by a Honda Civic at 20 mph or someone on a bike at 20 mph, I'm picking the Civic. Basically any car low enough that I can go over the top of, I'd rather get hit by that than a bike.
I would rather get hit by a bike than an F-150, though. There's no way I'm going over that, I would definitely end up under it.
Err in frontal collisions, maybe? But in pretty much every other case, having something with more kinetic energy will product more harm - it's physics after all. You don't see cyclists killing each others' a lot after all.
A 30 km/h car is also a lot less likely than a 50 km/h one to hit a cyclist or pedestrian in the first place - far shorter braking distance, and longer time for the slower mover to spot and avoid them.
Also, as someone who is both a cyclist and a driver, there’s a bit less urgency and frustration to pass a 15-20 km/h bicycle when you’re only allowed to do 30 anyway than when the limit is 50.
Also the speed is not so different. The speed difference is even greater between bicycles and pedestrians yet you see places where they mix them. As a pedestrian I have been passed by cyclists which disappear much faster than a car when a car passes me as a cyclist.
Well, a bicycle plus rider is about 100kg, which is a tenth of an old-fashioned car or closer to a twentieth of a SUV, so that should correspond roughly to getting hit by a car at about 1MPH.
I'm not awfully worried about cars moving at 1MPH, and correspondingly unworried about bicycles. You may disagree. Do you happen to drive a car? At 1MPH, or faster?
Let’s say the ratio of violations per mode is the same. In the city I live in, bicyclists make up <1% of road users. So the drivers operating their vehicles dangerously out number bicyclists doing so 100:1. And vehicles are what are killing and severely injuring people, not bicyclists.
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