In Virginia, in addition to speed limits, another law on the books (and prominently posted on every interstate) is "slower traffic keep right". Regardless of your speed, if someone's going faster than you, you should be in the right lane. If you're only doing 10 miles over the limit and someone else is doing 20, both of you are breaking the first law but, if you don't move to the right, you're also breaking the second.
The idea of "slower traffic keep right" is much more a principle than a law. One I generally agree with, too! But as a law, how are violations even definable? Its thoroughly simple for an enforcement officer to gauge whether a vehicle is exceeding the posted speed limit, within a reasonable degree of accuracy. It's a simple comparison...your vehicles speed versus the posted speed, if A > B, you have a violation. But "slower" traffic keep right? Slower than what? The average speed of all vehicles on the interstate? The average speed of the top 50% of cars on the interstate at the time? Some other arbitrary construct? How about all cars moving slower than the fastest car on the interstate keep to the right? Then one fellow would have a run of the left lane, until someone else overtook him. Of course, this is all completely indeterminable in a practical sense.
So, to make sure I never run afoul of the law in VA, what exactly does the law say would be the offense I would commit in violation of this statute? Would it be driving in the left lane at a rate slower than another vehicle on the highway at the same time? Are many such citations handed out?
I view the left lane as a passing lane, and so I don't cruise down the road in the left lane. Occasionally I'll pass multiple vehicles so I might be in the left lane for 30 seconds or more, but I usually get over soon after, giving the right lane cars a small bit of berth so I don't seem like I'm swerving in front of them or cutting them off. So I'm good with the idea of a passing lane, and not obstructing it to block traffic. But most of the unsafe gits that swoop up on me in the left lane (even in just a few seconds as I pass a slow truck in the right lane) doing 80 or 90, and then park on my bumper to show their displeasure (another principle like "Slower traffic keep right" was to maintain a certain number of car lengths between vehicles per 10mph of speed, something that I've rarely seen aggressive passing lane residents abide by) are breaking the law, endangering lives, and driving unsafely, and then they have the unmitigated gall to blame someone driving with strict observance of traffic laws for being unsafe because they had to apply brakes on the highway while speeding.
EDIT: Found this on a "lane courtesy" website: "This means a driver going the speed limit in the left lane can still be a serious problem. They can cause abrupt lane and speed changes, as well as hostility or road rage." ROFLMAO! They might cause road rage? That's the equivalent of the old "dressing seductively causes rape" chestnut!