I think the core of the problem is the fact that posted speed limits are not enforced. Instead, an arbitrary number decided by a cop is enforced. For example, in a 55 mph zone, a cop would not stop anyone going 56 mph, and probably won't stop for doing 60 mph. But going any faster, some cops will let you slide up to 70 mph, while others may not. That is why drivers are confused and "playing it safe" when they see a cop, and slow down to get into the "safe" speed. At times, there will be a cop who will pull a driver for doing 60 mph in a 55 mph zone - just to get more money for the county. Very confusing to drivers. So, when they see a cop they do the only logical thing - slow down as quickly as possible.
The issue above is the result of yet another deeper problem - the speed limits on divided highways are too low in the first place - anyone can guess why - in the name of safety of course (and not to generate more revenue for the government, you silly). This other problem has its own set of consequences - slow drivers occupying the left lane because "they have a right", thus slowing everyone down and creating frustration for those who are unable to pass; LEO's are not concerned with making sure the flow of traffic is smooth - they are more concerned about enforcing the speed limit (or adjusted speed limit depending on how they feel on that day).
I think the speed limits can be set a lot higher in most places (not saying all places). I am sure many of us know roads where 55 mph speed limit is ridiculously low. I would say set it to 90 mph, and strictly enforce it. Modern cars, good roads, and ideal conditions can easily sustain such speeds. If someone is doing 91, then pull them over. If they start arguing about there speed being exactly 90 mph, tell them "it's the speed LIMIT - if in doubt don't get close to it - drive at 85 mph and be happy". Then, everyone would know that there is no confusion, that the speed limit is real.
I would also set a separate speed limit for bikes - 50% more than for cars - so 80 mph for cars would mean 120 mph for bikes (part of a motorcycle written test should be testing the ability to add 50% to any posted speed limit, LOL). It is fully justifiable - the bikes accelerate a lot better than 99% of the cars on the road, slow down better then 99% of the cars on the road, and swerver better than 99% of the cars on the road.