Though what you don’t get is the concept of inertia at the train’s scale. You can’t just say “mass cancels out”. The specific energy to stop is the same per given amount of mass, however the amount of mass is not in the same league. Not to mention the CoF differentials between rubber/asphalt to steel/steel.
I'd say the problem with simply saying that uncontrolled railway crossings should be banned is that railroads will understandably say that it will take time to comply, and then stonewall for decades because of funding/whatever. Whereas the standard of liability can be changed atomically after some notice period, and if the railroads haven't upgraded their crossings to be able to maintain the speeds they'd like, that's on them.
Also the framing is different - actively outlawing certain types of crossings is adding government regulation, while eliminating the liability shield is an elimination of corruption.
Doh. Stopping distance is proportional to the square of speed. I knew this was wrong when I was typing it out, but I convinced myself it was right. I must have been thinking of the time. Being the square of the speed actually makes my point stronger, as the speed doesn't need to be reduced nearly as much to obtain a given stopping distance.
Mass cancels out and is irrelevant. "Train is Big" makes for a great red herring though. And "propulsion system", really? I'm pretty sure they both use wheels to accelerate and decelerate, not reaction mass or gravity bending sci-fi tech.
Both trains and cars have stopping distances that are proportional to speed, with the main difference being the constant factor. Therefore, for any desired stopping distance, we can set a maximum speed. This is done with cars, where areas of heavy interactions (cities), speeds are low. Moderate interactions speeds are moderate, and the onus is still on cars to stop even though it doesn't feel that way. And there are controlled access roads where speeds are high and you're not practically expected to stop for pedestrians in the road (though obviously you certainly should try).
Currently train tracks are treated as if they're controlled access, while often having few controls. That's the problem.