Motor vehicle accidents are a leading cause of traumatic brain injury related deaths. If you are under 55 the obly higher cause is suicide. (If you qre older than 55, your chances of a TBI related death from an accidental fall start to skyrocket with age.) There is a reason why race car drivers wear helmets, and it isn't just to have another place to plaster sponsor logos.

I am not aware of any studies looking specifically at the effects of helmet wearing on TBI rates of regular drivers, but then good data on that for bicycles is also hard to come by but that doesn't stop people from pushing for bicycle helmets.

Race car drivers are at a lot higher risk of a collision, spin, vehicle fire, or rapid disassembly in general than general traffic. And in many forms of racing, they usually go significantly faster than general traffic too. Helmets, neck restraints, five point harnesses, and flame retardant suits all reduce risk of injuries, and would likely reduce risk in general traffic as well, but the risks seem low enough that the expense (including time to equip) of that additional equipment is too much to justify its general use. Although, if there were an easier intervention to help with neck injuries, it might likely be adopted.

> And in many forms of racing, they usually go significantly faster than general traffic too.

Yet, lethal TBIs are more likely to come from motor vehicle accidents than from bicycle accidents.

> the risks seem low enough that the expense (including time to equip) of that additional equipment is too much to justify its general use.

Yet, somehow this argument is deemed irrelevant when helmets for bicycles are discussed.

There really is not a compelling reason why helmet usage in a car is different from on a bicycle. The main difference is social acceptability, not any objective risk analysis.

> Yet, lethal TBIs are more likely to come from motor vehicle accidents than from bicycle accidents.

Is that per mile, per minute, or per lethal TBI? Also, is a collision between a bicycle and a motor vehicle a motor vehicle accident or a bicycle accident?

Of course, bike helmets protect against more than just brain injury. They also protect against road abrasion of some portion of the head, which is not usually a factor for car occupants, except if they're ejected or they're in a car that rolls over and doesn't have an roof or an effective roll bar.

Bike helmets are much lower expense and hassle than car helmets (which are mostly motorcycle helmets) and neck restraints, etc. If it's a public use bike system, especially the leave anywhere bikes, the expense and hassle gets overwelming, and helmets for customers of a pedal cab would be similar.

I've got a bike helmet with integrated lighting, which adds functionality and is kind of neat, although it was much more expensive than a good enough helmet.

> per lethal TBI?

Per lethal TBI, I don't think the data exists for per mile or per minute.

> Also, is a collision between a bicycle and a motor vehicle a motor vehicle accident or a bicycle accident?

Good catch, looking at their methods, they do include IDC-10 codes for pedestrian and bicyclist injuries due to motor vehicles in that number so I am not sure how many of those are actual vehicle occupants and I can't find any data at the moment that breaks those numbers down per IDC code group.

> Bike helmets are much lower expense and hassle than car helmets (which are mostly motorcycle helmets) and neck restraints,

Not that it correlates much to every day driving, since both speeds and driving patterns differ, but e.g. NASCAR drivers wear helmets (along with that whole neck protection setup that latches to the helmet).

I don't know, however, if a helmet may work worse in conjuction with an airbag though. So personally I think I'd stay away from helmets in cars (but I really have too little data to make an informed decision).

Having said that, in the case of this company, perhaps they could offer their passengers a "Hövding" device? (Hövding being the swedish word for a chieftain, but "hövve" is also slang for head, and in the case of this product it is a... "backpack/necklace thingy" that is a wearable airbag. Supposedly works really well, but probably comes with a price tag matching this function.

If you take your car to a track day it’s generally required that you wear a helmet (and a bicycle helmet wouldn’t qualify).

All rally drivers wear helmets. Pretty sure its not just to have more sponsor stickers.