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Comment by tda | Hacker News Reader

No you wouldn't: a car-pedestrian accident at 30km/h gives you about a 5% chance to die. https://ec.europa.eu/transport/road_safety/specialist/knowle...

With a bicycle I'm quite sure the odds of a fatality are <<1%

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Ok, I’m prepared to stand corrected. 30km/h is probably a bit to high speed, although data vs bike is hard to find.

Getting hit by a bike a 30km/h might well get you killed though, judging from the state of my friend mentioned above.

A bike have no deformation zones and no slick surfaces to slide along.

Thank you for enlightening me with some numbers though.

While a bicycle probably isn't going to be going as fast as a car, at equal speeds bicycle collisions aren't going to be that much less dangerous than car impacts. 30 km/h is a quite attainable speed for a bicycle. I definitely wouldn't assume <<1%.

"When considering the average length of hospital stay, the majority of pedestrians involved in collisions with cyclists were admitted for fewer than two days (53.1%), while only 7.7% required a hospital stay greater than 7 days. Compared to pedestrian collisions with motor vehicles, the duration of hospital stays were significantly shorter (χ2(1)=27.5, p < 0.01, φc=0.06), furthermore the severity of collisions were also significantly lower compared to collisions involving motor vehicles (χ2(1)=9.85, p < 0.01, φc=0.04)."

(But I don't know what the figures mean.)

https://doi.org/10.1016/j.aap.2018.10.018 at https://s23705.pcdn.co/wp-content/uploads/2018/12/Pedestrian...

You unfortunately miss the huge difference in mass and thus impact force. I guess it will make at least some difference.

A 100kg cyclist + bicycle vs a 1500kg car (+ driver)

I would take in to account the hard stop.

A modern car have deformation zones and angles for you to basically slide along - you will never get the impact of that full mass.

A bike, well, you will come to a hard stop and it’s got metal rods sticking out here and there.

Getting hit by a bicycle at high speed is worse than what you’d expect, at least according to my personal experiences.

> A modern car have deformation zones and angles for you to basically slide along -

That protects the people in the car, not those outside. Being hit by those deformation zones _will_ hurt.

There is one thing that makes modern cars less dangerous to pedestrians, and it's that when someone is hit by a car they are more likely to roll over the hood than under the wheel. HOWEVER this is only the case for sedans, and definitely NOT for SUVs. Now look at the proportion of SUVs in your area.

Deformation zones are designed to protect the car's occupants in the event of a collision with a tree. They are not designed to protect a pedestrian. (Although some modern cars are beginning to have proximity sensors that can launch an automatic emergency brake. That would help the pedestrian. The deformation zone certainly doesn't.)

None of which is meant to imply that being hit by a speeding bike is harmless, of course.

> Deformation zones are designed to protect the car's occupants in the event of a collision with a tree. They are not designed to protect a pedestrian.

Nonsense, all modern cars have deformation zones specifically for protecting pedestrians during collisions. All modern crash tests by EuroNCAP etc. have tests for such impacts and current results speak volumes for the improvements in this area.

https://www.euroncap.com/en/vehicle-safety/the-ratings-expla...

Here's the ratings for the Tesla Model 3 vs. pedestrians for example: https://cdn.euroncap.com/media/54117/pedestriancrashimage.pn...

You can see clearly the impact of the very soft bumpers designed specifically for such crashes.

I seem to find several papers and books discussing pedestrian saftey in regards to bumper, hood/bonnet design and crumple zones.

I’m no expert by any means, but I’m certain though that pedestrian safety is considered when it comes to car design.

Having a crumple zone that absorb energy seems like it would work in favor of someone getting hit as well?

About 80% of the cyclist+bike combination is made of more or less squishy flesh.

> No you wouldn't: a car-pedestrian accident at 30km/h gives you about a 5% chance to die.

That would be including the accidents where the car never stopped, e.g. backing out from a garage and running over a toddler the driver didn't see.

So, your argument is that with the exception of cases where a car is more dangerous than a bike - both are equally dangerous. You don't say.

The discussion started by referencing ~30km/h collisions.

Not someone slowly backed over by massive vehicle, which is most likely included in the death count.

Slow backing car vs slow bicycle? I take impact with slow bike every day.

That's probably true, but death isn't the only negative outcome. I'm regularly buzzed from behind by bicyclists passing me at high speed on sidewalks. It's quite unnerving, since most of our local cyclists are idiots, generally untrained, unable to quick stop, and often riding without any brakes at all.

I've taken to carrying an umbrella everywhere, swinging it quite dramatically as I walk. This seems to be an effective way to cause cyclists to keep a safe distance.

I’ve seen the result of a man getting hit by a bike at ~30km/h.

Just awful. He barely survived, being reasonably fit and not too old/weak.

If it was my choice - yes I would, assuming a somewhat modern car.

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