(07-01-2022, 03:10 PM)Cormanus_imp Wrote: Tommy, there’s some stuff on the [url=https://motocap.com.au]MotoCAP site rating various items of riding kit, including helmets. The methodology is described.
For helmets, there’s also the UK [url=https://sharp.dft.gov.uk]Sharp site.
I had seen the sharp site, but not motocap. As you say, the methodology is described, but has to do with impact and abrasion tests rather than actual study of outcomes. The Sharp methodology does at least correlate accident data with the likelihood of certain kinds of impacts, and then rates helmets based on their ability to protect those types of impacts in lab tests. The site doesn't have open face helmets rated at all though. In any case, the methodology is different than doing a large study where you correlate real world injuries with the type of helmet actually used.
The US NIH did such a study that showed that 3/4 and full-face helmets were better than "half-helmets", but that there wasn't a statistically significant difference between full and 3/4 face in terms of "lasting or significant" head injury, though they were quick to point out that more data was needed.
The motocap site does rate open face. A similar Arai open face to the one I showed scores 3 stars out of 5, where high-end Arai racing helmets score 4 out of 5. I guess that's "one better", sort of like a Marshall amp, but it's not clear what to do with that.
Anecdotally and common sense wise full face has to help in an accident (just look at Aussieflyer's photo!). But anecdotal and common sense doesn't always take into account other factors. If, for example, the added visibility in a 3/4 helmet makes it less likely to get into an accident in the first place (not saying that it does...but it could) or if for whatever reason people instinctively change the way that their head and body react in an accident while wearing such a helmet (not saying that they do). that isn't captured in test data from sites like this, even assuming that the methodologies are valid (which is sketchy in some details).
I'm a pilot and happen to fly a Cirrus. These planes are popular for their efficient composite designs but they also contain a full airframe parachute to be used in the event of catastrophic failure. Counterintuitively, the planes had a worse safety record than similar planes without the parachute for over a decade. It turns out that the parachutes influenced pilot behavior. It took a concerted training effort with owners of the entire fleet for the next decade to bring the safety record back in line.
Anyway, none of this is to say that full face helmets aren't the best. I find topics like this interesting to explore though.