Actually, train systems having its own assigned branches of police is common enough that there's a Wikipedia article[1]. Unique part is that the US doesn't have an umbrella national or state agency that such branches would be part of.
They're not actually "assigned branches" of the police, they're private police. The US/Canadian railway police are not government employees, they're employees of the Class I railways and deputized with general law enforcement powers. They're spiritual successors to the old timey Pinkertons.
Two of the biggest are Canadian National Police and Canadian Pacific Kansas City Police -- and those two are deputized, in both Canada and the US, with Federal, State and Provincial police powers. Despite being railway employees they can cite you for, e.g. speeding if they catch you doing so. Either on or off railway property.
BART exists in 5 counties (San Francisco, San Mateo, Alameda, Contra Costa, and Santa Clara) and multiple cities (SF, Oakland, San Jose, and multiple smaller ones).
Having people who have jurisdiction in any bart station is useful. And for example, consistent foot patrols are valuable to BART but not necessarily valuable to the city of Hayward, or whatever. As a concrete example, BART has more or less a goal to be able to put an officer on the car within a stop or two if you report on the app. That's logistically challenging for like a half dozen reasons if the bart police wasn't it's own org.
That's a good question, any I have no idea of the answer, but the port authority of NY and NJ has it's own police. I always figured it was because it spanned jurisdictions, but perhaps there are other reasons
https://en.wikipedia.org/wiki/Railroad_police are actually a thing! It's not just transit either. Most of the big US railroads have their own private police forces. The officers are deputized by the state, and then by federal law their powers are valid in any state that railroad has track. They even have arrest powers.
Hm, maybe CPD has a CTA detail then? I thought there was (or used to be) a CTA police division that had their own uniforms, cars, etc. I seem to also remember a CHA police for the housing projects, but it's been a long time since I lived there.
Presumably because police usually only have jurisdiction within their employer’s city limits, and sheriffs’ employees only have jurisdiction within their counties, so if mass transit moves between multiple jurisdictions, then their police can have jurisdiction wherever the mass transit goes (even across state lines, because a lot of metropolitan regions served by the same mass transit system span two or more states).
Most city police and sheriffs officers have jurisdiction anywhere in their state, AFAIK. They typically stay in their area, but if they’re pursuing a suspect they don’t break off if they cross the city limits.
It's pretty common around the country. If it isn't a separate entity you end up having a department of the normal local police doing it separately anyway. Also BART goes through several different police jurisdictions and trains... move. I can imagine the mess and disagreements about which police department was responsible for answering a call or riding in a car as it moved between cities/counties.
It's a chain of command (i.e. BART police report to BART, Campus police report to the school, way less messy than BART or the school having to convince the jurisdiction how to police the area) and prioritization thing. Bespoke police agencies exist to police their niche to an extent that would be unjustifiable if it were coming your normal police department and taking resources away from their other tasks.
Transit police, campus police, DEA, ATF, etc, etc, etc. Their entire job is to harass people that the equivalent generalist police couldn't justify allocating resources toward.
Irate homeless? SFPD won't show, but BART Police will.
Drunk college kids shenanigans? Normal cops don't care, but campus police does.
Weirdos making machine guns or huge amounts of LSD? FBI don't care as long as you're not trafficking, they got real crime with real victims to chase. ATF and DEA care though.
Wash rinse repeat this pattern for literally every bespoke police agency.
Yeah, jurisdiction can be a theoretical reason for these agencies but once again it's still a priority thing. When agencies care jurisdiction and coordination isn't a problem. Having one agency span multiple only helps if you're chasing stuff so petty it would get dropped.
Except for the last one in your list, the others are quality of life problems. I have no problem if police interfere with either. Even the last one, is at best borderline. If there is a weirdo making machine guns in my neighborhood and I have kids, I sure as hell want police to interfere.
That works in theory, until the police are overrun with things they don't specialize in and don't have the officers to handle the day to day plus illegal arms dealers.
why does a transit system need its own police force? Aren't municipal and county police enough?