Failure to yield the left lane is often caused by nothing more sinister than someone not paying attention. This can still be dangerous, which is why it’s a good idea to merge right if you are not passing anyone.

Unfortunately, there are also people who deliberately refuse to practice lane courtesy. These "left-lane hogs" have all sorts of excuses for their inappropriate and unsafe behavior. They say the left lane is smoother or that it’s easier to see from. Some even claim they are doing faster drivers a favor because faster cars can stay in the right lane and don’t have to pull out to pass them.

The granddaddy of all "left-lane hog" excuses is "I’m driving the speed limit, I shouldn’t have to move over." Of course, anyone who honestly looks at speed limits on our roads know they rarely reflect actual travel speeds. Instead they are arbitrary, politically generated numbers that have no relationship to real engineering standards.

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. Even if our speed limits were more realistic, there is no good reason to remain in the left lane if a faster vehicle wishes to pass you. It only creates friction and makes our roads more dangerous.

That’s why most states have laws that regulate driving in the left lane. Some allow it only for passing, others require slower traffic to yield the left lane if a faster vehicle is approaching. To find out the law in your state, click here.