A helmet has probably saved my life several times when riding my bike. In all cases, it was only me, my bike, and my idiocy involved, no third parties. All it takes is a little bit of loose gravel where you don't expect it, or a wet stone in the path that's a bit slippier than expected.

Bicycles with helmets are fairly safe. Without helmets? No way, I'm not riding without a helmet. But scooters without helmets are much worse, I wouldn't dare go much more than 10mph on a scooter without a helmet.

Hmm, What kind of bike at what kind of speed on what kind of surface?

It's entirely possible to ride a bike in a way that actually doesn't require a helmet. It's VERY boring :-P , but nevertheless practical and doable.

Probably about 15 to 20 mph. Once on a country road going down a hill in a bend; I slipped on loose gravel and had to replace my helmet. The second time, about the same speed but on a country bike path (flat land, next to a canal). I slipped on a large wet stone embedded in the path and again had to replace my helmet.

I've fallen a few other times besides those two, but those are the worst two and I think without a helmet I would have been seriously injured if not dead.

I ride without a helmet and essentially never go beyond about 12 MPH, and more often in the 6-8 range. I take sidewalks generously, stay out of mixed traffic, and frequently stay in low gear, and this is still over twice as fast as an average walking pace.

I think it's all relative to how much you're approaching it as "road cycling" vs "urban commuting". If you keep the seat high, lean forward, and pedal near your limits, you definitely need protection even if the road is empty. But if you're going at a pace and a posture that lets you stomp your foot down easily, the dangers come down to total loss of control(e.g. downhill, failing brakes) and unpredictable traffic.

The biggest danger with electric mobility going forward lies in blurring of the distinctions. When they're brought up to highway speeds, what you have is an underbuilt motorcycle with no safety features or licensing requirements.

Don't forget wet leaves. I was riding my bike well after it had rained, and most of the path was dry, but there was a shady spot under a tree that still was wet and I basically lost all traction on it. Only time I ever "used" my helmet.

Or half buried campfire rings (aka a repurposed truck wheel rim) hidden by the grass on the side of a hill.. I think I must have done about two flips in the air after hitting that. At least in that case I don't think I hit my head hard, I landed in the same grass which cushioned my landing, but if there had been something else hidden in the grass I might have lost more than just a bicycle wheel.

Ordinary upright/city bicycles have significant controllability problems at high (>50 km/h) speeds compared to e.g. cars. I think that's where "even bicycles" comes from, in this context.

(Why am I using >50 km/h as the benchmark? Because that's the sort of speeds you easily end up at if you try to keep up with cars downhill.)

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Edit: it seems that people are missing critical words in my comment:

- "Ordinary upright/city bike" means "not road/touring/etc bikes". They are constructed differently and comfortably do well over 50 km/h.

- "Downhill" means significant gravity assistance for a few seconds up to a minute, and not "sustained under pedaling power alone". I'd be impressed if you regularly did 50 km/h on the flats with one of those bicycles.

To be fair, if you're holding a professional cycling race, you should probably close off the roads to other traffic.

>Because that's the sort of speeds you easily end up at if you try to keep up with cars downhill

Not many people will do >50kmh even downhill (even with disk brakes), and on the few occasions I've done so, I absolutely would not say there are "significant controllability problems". In fact, quite the opposite.

[1]https://www.youtube.com/watch?v=FN6Z8UgVOuw Nb - these were shot in the days before the 'supertuck' (sitting on the crossbar) was banned.

I easily hit 35-40 mph on every commute to work with my bicycle on one of the downhills. Just 30mph is trivial to get to on any of the downhills with my bike, and is just slightly faster than many of the ebikes go with very little effort.

> Ordinary upright/city bicycles have significant controllability problems at high (>50 km/h) speeds compared to e.g. cars. I think that's where "even bicycles" comes from, in this context.

Who on earth is using ordinary city bikes at 50km/h near cars? Even class II e-bikes are limited to 20mph/32kph.

Class III are limited to 28mph/45kph but are forbidden from bike paths.

[edit] 50kph under your own power is the average speed at the Tour de France.

I used to commute from Bellevue WA to Kirkland WA, the mainly way across the freeway was either to go down this road over the freeway that didn't used to have sidewalks https://www.google.com/maps/@47.6393386,-122.2032674,17.25z or go 2 miles out of the way and up a huge hill. The right lane is where people wanted to go to get on the freeway at the time. It was easiest to just get in the left lane and do 40mph down the hill which is what cars did speed wise. People gave me plenty of berth if I was moving at car speeds. If I went slow on the right I got tailgated.

My bike was quite stable at 40mph.

No I wouldn't go that fast on a bike path, this was only due to the power of gravity.

As I mentioned in sibling response, it is somewhat easy to get those speeds in any hilly place. Keeping them for extended times is, of course, out of the question. And my return commute has me well below that. Again for obvious reasons. :D

Now, I fully agree with the spirit of your post. Even the spots I'm talking about are short bursts.