This gets on my tits more than anything on the road. Why are people such arseholes? You get two lanes going into one, and of course the idea is that each car leaves enough room for another to get in, whether from the the left or right. Some understand this but unfortunately many people are so aggressive and territorial that they will purposely drive as close as possible to the car in front so that no one can get in, as this may make them potentially a half a second later than they were.
Are we all supposed to drive in just the one lane (usually the left) leaving the other one empty?

This is a particular pain in the arse on dual carriageways when one lane is signed as being closed in 2 miles, so everyone quickly gets over to the left, creating a queue twice as long as it needs to be, snarling up roundabouts and junctions behind.