Australia is one of the few countries that require cyclists to wear helmets, by the force of mandatory helmet laws. It was actually the very first country to introduce legislation like that, with the state of Victoria passing the appropriate bill in 1990, and then having it spread to the entire country over the following 2 years.
I cycle to work every day (unless the weather is horrible), and every time I grab my bike I have to remember to wear a helmet. If I don't, I'm risking being stopped by law enforcement and being fined for $319. Though the amount is unique to NSW across other states, where the penalty is much lower (for example, it's "just" $50 in the WA), it's illegal there as well not to wear a helmet while cycling.
I'm not an expert in the topic of public health, road safety, and I'm but an occasional cyclist, so most of what you read here is my opinion based on my own riding experiences and a very brief research (less than a few hours googling). I think that research into the matter is harder than most people think, because there are multiple factors in play. It’s easy to compare any country with the Netherlands and say that the bike’s usage there is much higher, without mandatory helmet laws, and somehow people are not injured more often, while ignoring much more developed cycling infrastructure that the Dutch have. It’s easy to say that wearing a helmet makes your head 70% more protected when you fall—but maybe it’d be better to focus on not making you fall in the first place?
I have also already stated my opinion in the title of this post, so I’m biased against mandatory helmets. This leads to increased temptation to cherry pick convenient arguments and research, and value them higher over whatever the other side says. Moreover, as much as it’d be interesting for me to dive deep into the topic and compare all available data, I feel much stronger urge to just speak my mind and rant for a bit.
On one side, we have all the governments and government agencies telling about the benefits of wearing helmets. I wouldn't expect them to say anything else, given that their job is to ensure that the law is observed.
For example, I found out that Vicroads links to a Australian Health Protection Principal Committee paper from 2016 advocating for mandatory helmets. However, when you read into it, you might find excerpts like these:
The introduction of MBHLs in the early 1990s followed a campaign to voluntarily increase helmet-wearing rates across the population, particularly among children and adolescents. After the introduction of the laws, wearing rates increased from approximately 37% (1990) to 83% (1992).
What they mean: we introduced mandatory helmet laws, where not wearing a helmet can get you fined, and then—surprise surprise—helmets usage has risen! That's not really a proof of society wanting to wear them.
And here's another one:
These arguments suggest that the community will need to decide if it is willing to accept increased deaths and disability as a trade- off for eliminating the requirement to wear a bicycle helmet. In a road safety context, with campaigns underway to eliminate deaths and serious injuries, this position becomes indefensible.
Since the goal is to eliminate deaths and serious injuries, you could argue further that banning everyone from roads altogether would decrease deaths and injuries on roads to zero.
Other state government's websites weren't as thorough, and only mentioned some vague research or just quoted the law without going further into explaining why (eg. NSW, QLD, WA). Most of the argumentation from the government side I found was along the same lines: after the introduction of the law, helmets usage rose (🙄), while cyclists' head injuries and fatalities fell by some 30-40%.
On the other hand, there are parties strongly advocating against mandatory helmet laws. For example, this website is extremely thorough going way, way beyond all the information you'll find in this post. Especially the page with all the research compiled (bonus points for linking to the actual papers). I also found this Bicycle Network's paper from 2018 (direct link to the paper), which looks thorough and balanced, and does not explicitly say that helmets are evil, but just asks for a trialled relaxation of the law.
I think the main argument I gathered from the opposing side was that the mandatory helmet laws were not the cause of the fall of head injuries and fatalities, but just correlated with it. They attribute it to the overall increase of safety on the roads, since the number of fatalities among other groups (drivers, pedestrians) also fell by a significant number. In other words, correlation ≠ causation.
Oh, and also for what it's worth and if it wasn't clear by this point, I'm against mandatory helmet laws as well.
What does it mean to me?
Usually, when I get on the bike, I've already changed to my cycling thermoactive clothes. Remembering about one additional piece (the helmet) is not a problem then. But if I wanted, for instance, just get the bike to do a short trip to a nearby café, I wouldn't bother with changing clothes… and yet I'd still need to wear that helmet. And do something with it after I arrive. I can lock my bike, which should deter potential thieves, but it'd be very easy to detach the helmet if I left it on the bike. Were I to take it with me, suddenly I have this bulky item in my hands or my backpack. Not fun.
Bike sharing is also not fun
Using public bikes or bikes from a sharing program has a lot of benefits, like not having to own the bike, or being able to return it at your destination and not worry about it anymore. It's a fast and convenient way of moving around the city, that can be decided on on a whim ("oh, there's a bike here, let's rent it instead of walking").
Unfortunately, when you couple that with mandatory helmet laws it turns into an ordeal. You cannot legally ride a bike like that without a helmet. In the best case, the helmet will be attached to the bike. But more likely it's been already stolen (the story describes e-scooters, but it's the same for bikes) and unless you carry your own helmet with you, you're out of luck. But having to carry your helmet at all times goes against the convenience: now you're walking everywhere with a bulky helmet in your backpack or in your hands.
Helmet producers conspiracy theory
It's just one giant conspiracy. Think about it: if you buy a bike, you have to pay extra for the mandatory addition. And not just any addition: it must be compliant with the AS/NZS 2063:2008 standard, which is the base to the legislationSince the law that applies to everyone is based on the standard, it is accessible and available to all, for the small price of $91.64. What the hell?!. It will cost you around $20 for a cheap helmet, and from $50 upwards for one that also feels good on the headI found this nice article explaining the process of certification, and—due to its strictness—no safety difference between differently priced helmets. So a cheap $15 helmet from Kmart will be as safe as a $300 one from a hipster bike shop.". Prices north of $100 are not uncommon. Who profits from that? Of course, bike helmet producers!
Not really. But sometimes I like to think that it's not just a stupid law that's not sexy enough for lawmakers to repel. It sounds much better if the enemy is some Evil Oligarchy conspiring to squeeze the money out of innocent bike riders, and thanks to its evil doings the law has still not been abolished.
To sum it up
Riding bikes is fun. Wearing a helmet while doing so can be alright if it’s your choice. It’s not fun when you’re forced to do it under a heavy penalty.