A 2006 study showed that “280,000 people in the U.S. receive a motor vehicle induced traumatic brain injury every year” so you would think that wearing a helmet while driving would be commonplace. Race car drivers wear helmets. But since almost no one wears a helmet while driving a regular car, you probably fear that if you wore one you would look silly, attract the notice of the police for driving while weird, or the attention of another driver who took your safety attire as a challenge. (Car drivers are more likely to hit bicyclists who wear helmets.)
The $30+shipping Crasche hat is designed for people who should wear a helmet but don’t. It looks like a ski cap, but contains concealed lightweight protective material. People who have signed up for cryonics, such as myself, would get an especially high expected benefit from using a driving helmet because we very much want our brains to “survive” even a “fatal” crash. I have been using a Crasche hat for about a week.
OK, so 42k injuries/9k deaths is sobering, but does it justify wearing a driving helmet? I've been curious about this topic and also walking helmets for a while and now that I have my own car again (ironically, given the datasets here, an old 2000 car), the topic of reducing car risks is also of some personal relevance. I'm going to give a stab at a quick and dirty decision analysis here to get an idea of how the case for driving helmets look.
First, we want to convert the absolute numbers to a probability of injury/death per mile driven:
in 2001, the American population was 284,970,000 (note that injuries/deaths also happen to people who are not the driver, and most people spend a fair amount of time in a car, one way or another), so that's an average annual mileage of 9,018 which sounds pretty reasonable So:
deaths:
8819 / 2569980000000
= mortality risk of 3.431544214e-09 per mile driven42000 / 2569980000000
= injury risk of 1.634253963e-08 per mile -total risk of either mortality or injury of3.431544214e-09 + 1.634253963e-08 = 1.977408384e-08
(we just sum, since the CDC numbers seem to be mutually exclusive)So if you drive 5000 miles (roughly what I currently drive per year), then you have a risk of death or injury of
5000 * 1.977408384e-08 = 9.88704192e-05
.For mortality, we could say the expected loss this year for our 5k driver who is 30 years old is ~50 years at the usual \$50k/QALY, without discounting, would be
5000 * 3.431544214e-09 * (50 * 50000)
= \$42. That's just the first year, while 30yo, and each year the loss shrinks since you get closer to death; a quick hack to sum the series to get a total expected loss with discounting at the usual 3%:Injuries is more difficult. Browsing through a few papers on TBI and QALYs, I find QALY/life-expectancy losses from TBI in juveniles: "Measuring the Cost-Effectiveness of Technologic Change in the Treatment of Pediatric Traumatic Brain Injury", Tilford 2007 The estimates are kind of shocking - TBI is a very serious problem. (Not too surprising after looking at "Quality of Life After Traumatic Brain Injury: A Review of Research Approaches and Findings" and some of the citations in "Is aggressive treatment of traumatic brain injury cost-effective?" Whitmore et al 2012, or when I remember that a lot of military veteran dysfunctionality is probably due to TBI.)
Whitmore et al 2012 reports similar QALY estimates for adults; for example, QALY drops from 1 at #5 (healthy) to 0.63 at #4 on the Glasgow Coma Scale (concussion-like: "Opens eyes spontaneously / Confused, disoriented / Flexion/withdrawal to painful stimuli"), and 0.26 at #3. Details on estimates:
So Whitmore et al 2012 finds that a healthy 20 year old's expected (discounted) QALYs of 28.21 drops to 17.77 if he is hit hard enough to trigger a #4, which at \$50k again is a huge lifetime loss of \$522,000. For the 40yo, the same calculation is \$436,500. Splitting the difference gives me a \$479,250. The losses get worse with more severe Glasgow Coma Scales, where #1 effectively equals death. Since I'm not sure how TBIs break down by Glasgow rating, I can't do an overall expected value but whatever it is, it must be >\$479,250 since that was the least damaging scenario Whitmore considered. So the expected loss from a TBI injury but not death is \$479k (ignoring the immediate medical costs since those will generally be paid by other people like insurers or the government); now we again need to compute the probability of a TBI injury each year and sum the series:
So a quick estimate of the net present expected loss caused by TBI death or injury while in a car over a lifetime for a 30yo is -\$685. Or to put it the other way, we should be willing to pay up to \$685 to reduce our car TBI risk to zero.
For injuries
Rate should be 1.634253963e-08, yielding about $1261.78 lifetime loss.