It is not their duty to prevent crime, nor to protect the citizenry. They only try to catch the law breakers after the fact.
I realize we have nothing requiring the police to 'serve and protect' but if they see a crime about to happen the supposition will be they will do what they can to prevent it.
If a cop sees someone about to rape a woman .... are they going to hide and let it happen or will they try to prevent it? Knowing they aren't legally duty bound I still think they would work to prevent it.
If a cop wants to prevent speeding, in most cases simply being visible does the trick. Hell, I have travelled through many states where funding was down and they simply parked empty cruisers in the median to slow traffic. But in most cases the cops will find a nice little hidey hole to wait for the evil time savers known as speeders.
I admit, I speed regularly. I'm a safe driver but if I'm caught I pay my fine and go on my way. I know I'm breaking the law but for me it is civil disobedience. I don't agree with the speed laws. I will tell you I definitely slow down when I see cops around so it still begs the question; Why not prevent the crime (because they all say it is a killer) rather than write the ticket? If the answer is anything but revenue I'll be shocked.
KC