Bike helmet analysis
First, we should calculate the expected benefit (risk reduction) of wearing a bike helmet. This is, in fact, devilishly hard to find because people don't trust the foolish public with numbers. However, we can calculate it from these statistics:
<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3503925/>
This study looks at both head-related and non-head-related cyclist deaths over a long span of time. We can calculate:
- There were 29 helmeted cyclist deaths from non-head-related causes.
- There were 5 helmeted cyclist deaths from head-related causes.
- However, based on the proportions of helmeted cyclists who died from non-head-related causes, we should have expected to see 14 helmeted cyclist deaths from head-related causes if helmets offered no protection at all.
- Hence, the number of expected deaths saved is 9, or 9 / (29 + 14) = 21%.
Next, we must calculate the total risk of bicycle accident death. According to this page:
<https://www.calbike.org/urban-transportation-research-bike-fatalities/>
In the US, there are six bicyclist deaths per 100M kilometers of riding. Riding in heavy urban traffic, we might expect a typical speed of 25 kph, so this equals 1.5 deaths per million hours or 1.5 micromorts per hour. Helmets would therefore save around 20% of that, or 0.3 micromorts per hour.
(Micromorts: <https://en.wikipedia.org/wiki/Micromort>)
If we assume average remaining life expectancy of sixty years, there are then a total of 60 \ 12 months \ 30 days \* 16 waking hours = ~345,000 remaining hours in life. Hence, one hour of life has equivalent value to approximately three micromorts, and 0.3 micromorts equals approximately six minutes. Therefore, assuming a one-hour cycling round-trip, helmet use saves an expected six minutes of life, which is not a lot but not nothing. If helmet use was as simple as wearing a seatbelt, it would clearly be a good idea.
However, unlike seatbelts, helmets are not simply a part of the bike; they are large, unwieldy objects which aren't very easy to carry or store. In my experience, it usually takes more than six extra minutes to wear a helmet, considering that one has to remember to put it on at the beginning, take it off, carry it around with you, find someplace to put it down, remember to go find it and pick it back up, put it back on, and so on for however many destinations you have. Hence, helmets are much less practical than seatbelts.
I do note that it seems like this problem could be solved if there was, like, a securely locking case which could be fixed to the back of the bike, and was large enough to carry a helmet and possibly other bike related objects (lock, repair kit, etc.). However, I don't know if this exists; when I got my bike, I got a basket which could be used for cargo, but it didn't fit on the back and isn't secure anyway. If this does actually exist, then I think it would make sense to wear one; if there is an easy way to acquire this please do let me know :)