This is a poor summary. The reduction in the number of cyclists is very easy to see as making things less safe for the remaining cyclists. The data is rather clear on that, oddly. The article even linked to the study they are basing that on at https://usa.streetsblog.org/2015/02/27/safety-in-numbers-bik....
Do we know the full causal factors? I'd wager not. But it is a testable hypothesis as much as "mandating helmets will save lives is." Per the evidence of this article, that hypothesis is on much shakier ground than your post would allow.
The "reduction makes it less safe" is quite common. When something is "common and normal" everyone works around it, when something is rare nobody expects it.
This is why you can have less pedestrian fatalities in cities where everyone wanders into the roads seemingly haphazardly than in cities where there are fewer pedestrians and they usually cross with the lights.
There are so many confounding factors in there that it would be laughed out of the room at any statistician conference.
No, it's not a "testable hypothesis." Maybe you can find a "natural experiment" where two localities are exactly alike, except one has a MHL and the other doesn't: like a city where two school districts with identical demographics are divided by an artificial barrier.
Even in your article, they admit the uncertainties:
> Do more people on bikes cause cycling to become safer, or does safer infrastructure attract more people to bike? There’s no conclusive evidence either way, but the answer is probably a mix of both.
> Your article is statistically naive and doesn't prove anything like what you think it does.
A major point here is that the burden of proof should be on the ones proposing to make something mandatory.
Intuitively you might think that mandating helmets would improve safety. But now we've got a plausible argument that it might not. At this point there should not be a mandate unless the proponents can conclusively prove that it actually helps.
Because if helmets make things safer, people are still free to wear them in the absence of a mandate. But if they don't, and you impose the mandate anyway, you are now actively causing harm that its victims have no way to mitigate.
I'd wager most of what they observed there is just "how well are cities build for cyclist" (prime example: Netherlands) and how competent average driver is (Germany) not some nebulous "safety in numbers"
bike infrastructure quality can be more important than quantity.
A lot of what we are getting for bike infrastructure in the US is horribly designed and often ends up being statistically more dangerous than no infrastructure at all.
A lot of our urban bike lanes, even the ones protected by barriers, fall into this trap. They make things safer in between intersections, but very few accidents happen in between intersections. But the poor design of the lanes causes increased risk AT the intersections. And the intersections were already where almost all the accidents happen. We have an epidemic of bike lanes designed by people who don't bike who have the irrational fear of being rear ended by a car as the #1 risk when that's actually one of the least common accidents.
The bad infrastructure puts more cyclists who don't really know what they are doing on the road and they don't understand the pitfalls of the lane design. So you don't see reduced bike-car collision rates.
The truth is the opposite: more bike infrastructure and safer riding conditions with fewer barriers (e.g., mandatory helmet laws, cyclist licensing — another stupid idea that comes up with regularity) brings more cyclists.
Of course this is also the case. I am just saying it is hard to get cities to prioritize investments in cycling infrastructure without a large number of users.
Apologies, I should not have indicated that it "proves" that this is so. Rather, it does paint a convincing picture that something is there. It is akin to a smell test, if you will.
So, yes, lets debate the confounding factors. If you can name some factors, they should guide us in how we would build tests to explore them. I didn't claim it was easily testable, but it is certainly testable.
Things are "testable" when you can control all variables except one (in this case, MHL). This is rarely possible in real life, except when a natural experiment presents itself:
So in this case, it might be "the same city, before and after MHL was enacted." Then we could graph the number of cyclists and the number of injuries, and you'd have something.
I would argue that things are "easily" testable when you can control all of the variables. For most of history, we have rarely ever controlled all variables outside of the easy cases. Typically, we define away much of the extra stuff. That has not stopped us testing what we can, just be sure to disclose everything else. Obviously, things are more confidently testable if you have controlled all variables, but that would be a crippling condition.
Basically, following the link in wikipedia will get you to https://en.wikipedia.org/wiki/Scientific_control which allows for "A scientific control is an experiment or observation designed to minimize the effects of variables other than the independent variable (i.e. confounding variables)." Which is much less strongly stated than what you have. The idea is still there, of course.
ok. It's not really a "crippling condition" when natural experiments do crop up from time to time, though.
For example: if Amsterdam suddenly had an MHL, that would be one. In fact, any city that instituted MHL would be a natural experiment. The number of riders, the number of accidents, the % of accidents that involve injuries -- all those things would change, while the city design and transit situation (other than bikes) presumably would not.
> The reduction in the number of cyclists is very easy to see as making things less safe for the remaining cyclists.
Perhaps that should be the headline then. "Mandatory Helmet Laws Make Cyclists Less Safe" implies that going helmet-free is safer than wearing a helmet. I get that there's a logical thread the writer is following re: fewer cyclists create a more dangerous environment -- we could also follow that logic when talking about rising bike prices or any number of things removed from the actual noggin-protecting benefits of helmets. Not sure I'd go so far as to call the headline "clickbait," but a more precise headline would've more accurately described the actual story (which was interesting to me, and I learned something).
No, it does not imply that. You may infer that, but you do so incorrectly. The sentence is clear, and is referring to "laws", not the usage you claim to be implied.
You are right: The headline "Mandatory Helmet Laws Make Cyclists Less Safe" is accurate in that the article you're about to read is about the _laws_, not the helmets. I stand corrected!
Do we know the full causal factors? I'd wager not. But it is a testable hypothesis as much as "mandating helmets will save lives is." Per the evidence of this article, that hypothesis is on much shakier ground than your post would allow.