Quick examination of miles per micromort for US drivers, with adjustments for safety-increasing behavior

by Josh Jacobson1 min read19th Apr 202114 comments

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This post links to a Google Sheet containing a quick investigation into the accuracy of Wikipedia's figure for miles per micromort (230) for US drivers, when accounting for preventative behaviors.

The following are the main outcome estimates:

Miles per micromort, no adjustments, in US (2019)91
-- If excluding motorcycles105
-- If excluding motorcycles and pedestrians, pedalcyclists, and other nonoccupants137
-- Amongst passenger vehicle occupants only132
-- Amongst passenger vehicle occupants only, if setting single-car crashes to 0235
-- Amongst passenger vehicle occupants only, if approximating the seatbelt-wearing only rate245
-- Amongst passenger vehicle occupants only, if setting single-car crashes to 0 and approximating the seatbelt-wearing only rate442
-- Amongst passenger vehicle occupants only, if setting single-car crashes to 0 and approximating the seatbelt-wearing only rate and if setting alcohol-impaired, drowsiness-associated, and distraction-associated deaths to 50% of current level (as an approximation of controlling one driver's behavior in two driver crashes)548

This rapid (~1.5 hrs including documentation) investigation was funded by Ruby Bloom via the Bountied Rationality FB group.

14 comments, sorted by Highlighting new comments since Today at 6:30 PM
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The quick examination didn't get into this in the final numbers, but I feel confident that time of day (day vs night) is a big deal. Deaths during the nighttime were roughly the same as daytime deaths, but I'd assume most of the driving happens during the day, and disproportionately deaths are at night, both for visibility or sleepiness reasons.

I would advise people against driving through the middle of the night. Even if you don't feel tired, it's not good to go against your circadian rhythms. 

Driving at night is not just about your own tiredness/circadian rhythm, there are other people driving tired and drunk. 

In my college town, there's a 1/4 mile long plastic-fenced in road, leading to rental houses. Every Thursday-Sunday night, someone will run their car into this fence, leaving broken fence marks the next morning. 

A dialogue between myself and Ruby that may be of interest (shared with permission): 

Ruby: A question: why do you set single-car crashes to zero? 

My response: It seemed you were interested in something like "if you're a safe person, how safe is driving", and I thought single-car accidents may be particular indicators of being 'unsafe' in some ways. I'd be happy to add calculations that include single-car accidents as well. 

Ruby: Maybe, but there are reasons why a safe driver might be a single-car crash too: 
- hit a pot hole, 
- lost traction in bad weather (rain, snow) 
- swerved out of the way of a another car (is that 1 car or 2 car crash?) or out of a pedestrian/animal/whatever. 
- general car malfunction (tire blown, steering, breaks) 

My response: Yeah I think what constitutes a 'safe' driver is pretty unknown, and I wasn't ultimately sure what adjustment to make. A perfectly safe driver, for instance, could arguably prevent each of these examples. Additionally, it's likely an oversimplification to remove all of a single driver's share of distracted and drowsy driving crashes, as there's likely some percentage of those that are unavoidable.

A perfectly safe driver, for instance, could arguably prevent each of these examples. 

A perfectly safe driver, hopefully could. My motivation for wanting to estimate micrmorts was trying to estimate the conversion between microCovids and micromorts for people in the Rationality community. Hence, I'm most interested in the level of safety Rationalists typically have (e.g. seatbelts, not drunk driving) vs population average, so this is pretty good.

If I could, I'd get every Rationalist driver to drive vigilantly ("defensively"), take a car-control/defensive-driving course (e.g. this one), keep their car well-maintained (e.g. tires inflated adequately,  inspected at least once a year). But most people's miles are in Uber/Lyft, which is maybe pretty good since those drivers are mostly (a) very practiced, (b) forced to service their cars more reguarly.

Additionally, it's likely an oversimplification to remove all of a single driver's share of distracted and drowsy driving crashes, as there's likely some percentage of those that are unavoidable.

I wish I could say I never drove when tired. 

My personal experience in Uber/Lyfts (pre-covid, I used them multiple times a week for several years) is that they're probably more dangerous than driving myself (>80% of rides are very safe / normal, but the 1-20% where I think they're driving too fast or recklessly seem like most of the risk). I personally would be happy to pay 10% more to guarantee a safer driver, especially on e.g. a rainy day. I think I probably have more experience driving than most Berkeley EA's though / feel more confident in my driving skills.

But most people's miles are in Uber/Lyft

This is interesting to me, as every time I've looked at Uber/Lyft prices in my area it has seemed a bit high for it to be my go-to option. Can you link me to a good discussion regarding why this is the typical Rationalist choice? (I've read a lot of the sequences, etc. but really don't spend hardly any time on the blog itself)

Nothing fancy. In the Bay Area it's lots of people's choice:

  • Rail (BART) usually won't take you the last mile or two.
  • Car ownership is expensive (just having somewhere to park is either expensive or your car is likely to get broken into), plus many people never learned to drive, and parking when you go places is a pain.
  • The buses are awful.
  • Uber/Lyft aren't that expensive in this area, or weren't when pooling with other random people.
  • People are too lazy to cycle. :P (also bikes getting stolen all the time)
     

I think I underestimated how much of the Rationalist community was in the bay area. That fact alone resolves most of my confusion, thank you.

Do you have a car? Most rationalists in Berkeley don't, so unless it's nearby or you're doing one of a small set of public-transit compatible routes, Uber/Lyft are the only option.

Also note that the amortized cost of owning cars vs Lyft are moderately comparable, and if you’re not doing that much tracking Lyft / Uber comes out a lot cheaper

Unfortunately, a car is an unavoidable cost for me, I expect that is a large part of the difference.

For sure if you have a car it doesn’t make nearly as much sense to Uber places

I do have a car, but I don't even live in the bay area and didn't realize how many of you were in Berkeley. Makes sense now.

So a micromort is one millionth of a fatality, so there has been one fatality every 91 million miles