[biophysboy]

Coming from a bio background, I’ve always been confused why auto fatality stats are normalized per miles driven. Epidemiological metrics like incidence or prevalence seem like they would work fine? Town A would be “safer” than town B if people’s commutes are 20% shorter, even if accidents occur w same frequency

[andrepd]

Because it yields a simple corollary that to make travelling safer you can reduce the number of miles driven. Mostly by giving people viable alternatives to driving, be it long-distance rail or bike lanes to move around quicker and safer in the city.

[Aloisius]

Pretty sure I've seen exposure-adjusted incidence rates used in clinical trials.

Miles is simply a proxy for exposure.

Given risk here does vary by exposure time and trip length varies so much, it seems reasonable to use - at least in combination with crude rates.

[biophysboy]

Fair point - a combo might be the best approach.. I understand the idea of accidents correlating w/ miles driven, but it seems to be optimizing for driving safety rather than human life? Does that make sense?

[_vertigo]

What are some other better ways to normalize?

[gsnedders]

Other common approaches:

1. Per capita

2. Per registered vehicle

3. Per trip

All of these have upsides and downsides (as does “per vehicle km”), and all will paint different pictures with different distortions.

[biophysboy]

Honestly, just per 1M person per year. If this normal incidence went up while the exposure incidence rate went down over 20 years, I'd wanna know.

[cozzyd]

Per trip?