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Comment by bquinlan | Hacker News Reader

In my social circle there is a perception that the BART is increasingly unsafe and some people who previously used the BART to commute from East Bay to SF are now driving.

Their perception seems to be born out by the data:

From the Bay Area Rapid Transit Police Department [1]

Aggravated Assault (2019): 112

Aggravated Assault (2022): 114

Relative increase (2019 -> 2022) adjusted for ridership:

114/112/0.3 = 3.39x

[1] https://www.bart.gov/sites/default/files/docs/2023-01%20Mont...

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This follows a general trend of roads becoming unsafer since COVID.

Traffic Fatalities in CA:

2019 -> 2020: +3.4%

2020 -> 2021: +7.6%

Unclear about 2021 -> 2022, I'd have to run the SWITRS data myself. Keep in mind these are just fatalities. I'm guessing crash data will show an even larger effect.

Source: https://www.ots.ca.gov/ots-and-traffic-safety/score-card/ and other OTS resources.

Is it possible that the amount of assault is relatively unrelated to total ridership? Like the number of criminal assholes in the community is about the same regardless of how many people use mass transit?

The point is that with a constant amount of assaults, and fewer potential victims, you are more likely to be a victim.

Only if you assume random victims of assault. That’s a pretty big assumption

How is this not probabilistic victim blaming?

I don't think it's victim blaming, it's a valid point.

Are you more likely to be shot on the streets of Chicago compared to Boise? Probably, yes, however you're MUCH more likely to get shot on the streets of Chicago if you're involved in gang related activities.

There are probably similar qualifiers for assault on the BART.

> There are probably similar qualifiers for assault on the BART.

No, not really. Unless you have data to back that up. Source: I was assaulted outside a BART station randomly.

One more data point:

> Rojas added, "It looks like it was an unprovoked, unwarranted, vicious attack."

https://abc7news.com/bart-stabbing-arrest-john-cowell-lee-oa...

One more

https://www.bart.gov/news/articles/2018/news20180408

Nobody is saying that there are no random assaults, they are saying that without data on what percentage of the attacks were completely random, we can't make assumptions that an increase in total number of assaults equates to an increase in total number of random assaults.

> Are you more likely to be shot on the streets of Chicago compared to Boise? Probably, yes, however you're MUCH more likely to get shot on the streets of Chicago if you're involved in gang related activities.

You made the argument that attacks are targeted using an analogy without having data.

I am not arguing that the increase of assaults on the BART are targeted. I am arguing that that without data to prove it, we are making an assumption by saying that an increase in the number of assaults on the BART means that you are more likely to be a victim of assault as a random commuter on the BART. I used an analogy of Chicago shootings because these numbers are well understood, I suspect the BART numbers are not as well understood (most of what either of us can find are anecdotes).

The logical fallacy here is the fallacy of composition. We've only been given the statistics as they relate to ALL riders of the BART (of which "random commuters" only comprise some portion of ALL riders of the BART). We can't draw conclusions about the likelihood of assault against commuters based on this data alone.

I rode BART for 16 years. It's not a big assumption.

Right, people with small statures who look like pushovers will face a disproportionate amount of the abuse. Big mean looking guys like me usually don't have much to fear, but why should anybody have to put up with it just because they're small and meek?

I guess criminals and insane people don't wfh.

I suspect so. I think in large part (but not all) the perception that San Francisco has gotten more unsafe since the pandemic is because our horrific social problems are now even more visible with fewer crowds around.

I suspect this is exactly the phenomena in action. You've got a relatively constant-sized population of deranged individuals who ride the trains a lot. When there's a lot of people on the train, they disappear into t.

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