It never really hit me until recently that they are 100% private business in the USA.
Keeping that in mind, what makes them any different then any other business hauling gas or haz mat? nothing really, no trucking companies have their own police, they dont have any obligation and many other RR's dont bother to employ a uniformed police department either, but your point is well taken and I stand corrected on my past statement of obligation to the RR, they are private out to make a buck and based in the USA, they have no obligation, the government bears that responsibility to it's tax payers including private companies