Ok, I didn't claim it's legal to make a pass at 200mph in a 35mph zone. I am not about to look up the statutes, especially as they are different in every state,

Ok, I didn't claim it's legal to make a pass at 200mph in a 35mph zone. I am not about to look up the statutes, especially as they are different in every state, but my memory is that at the end of the day speed is legally up to your judgement and the officer's judgement. 95% of the time the posted speed limit is treated as "The Limit", but in circumstances like passing we continue to use "judgement" as the metric, both on part of us and the officer. So if you pass at 70mph in a 35mph, an officer can say "That is reckless", and if you pass at 40mph he can say "That is reasonable". Remember, it behooves no-one for passing speeds to be +0.5mph. If you want to overtake someone and you cannot have an appreciable speed differential, the pass will take a very long time which is more risky.