There are lots of examples of people doing silly manouvres on the roads, mostly because they are oblivious of other vehicles around them, but this is one that people seem to do intentionally, as if it's a legitimate tactic. It isn't, and it's pretty annoying and dangerous, what's everyone else's opinions on it?
Imagine a large roundabout, with several exits, each to a dual carriageway. A car on the roundabout, perhaps on the outside lane or maybe moving into that lane from the inside lane, is passing one exit/entrance on the roundabout and is intending to leave the roundabout at the next exit. I've labelled this car as "X" on the picture below.
A vehicle is approaching this same roundabout from the exit/approach that car X is passing, I've labelled this as "Y". Y is supposed to give way to vehicles on the roundabout approaching from the right, (in the UK, anyway). Instead of stopping and letting X pass, Y decides to enter the roundabout straight away - intentionally - because he thinks X can move across to the right hand lane and still exit the roundabout.
So in my diagram below, car X was on the course shown by the red broken line, instead he has to swerve to the right, as shown by the blue line.
Yes, there are 2 lanes exiting the roundabout at each junction, but if car X is in the left lane (as he's supposed to be, as he was taught to do when he learnt to drive), then vehicle Y has to stop and give way. Is it not entirely wrong that Y pulls out - wrong because if X doesn't swerve or rapidly alter course, there will be a collision. So, IF someone chooses to do a manouvre that will cause a collision unless someone else takes avoiding action, isn't that 100% wrong? And yet many people do this, almost as if they no longer have to give way to traffic approaching from the right on a roundabout, as if they magically have equal priority to the cars coming from the right.