> It’s not just “undesirable groups”. It’s people stealing your stuff if you aren’t paying attention, stalking women, creating messes, or just harassing people who want to be left alone.

This seems to be a symptom, not a cause. The free zone, let me guess, more densely populated, city center area, and the not free zone, a bit less urban? Smells like income disparity zoning.

I mean if you think about, doesn't it seem a bit off to suggest that the prevalence of crime would be affected by whether a bus is free or not? My instinct is to get further into why there's crime happening at all, on or off bus. Why does it happen there, and not e.g. here in Taipei? Or other places with tons of public transit going on and very low crime, like Japan? The PRC?