So in Britain, overtaking is performed using the “outside lane”; in the US it is termed the “inside lane”. In both cases, it is a passing lane farther from the shoulder of the roadway. This video clip is set up today, was recorded on a highway in Bulgaria.
Both single lane and multi-lane overtaking manoeuvres involve risk and require extreme care. In this case, Saab driver was (Saab 9-5) Overtaking on the inside (undertaking) – he did not overtake another vehicle just once, but several times!
It’s clearly a case of dangerous driving which the motoring public in Blugaria would likely be appalled with.
If you have any doubts it is best not to overtake and to wait until it is safer. On the other hand, Driving slowly in the left lane actually causes more accidents than people who drive over the prescribed speed limit. Of course, if someone drives slowly in the left lane, that is no reason that you’re breaking the law. You must overtake on the left (in UK – right) unless a vehicle is waiting to turn left, is stationary, or if you and the other vehicle are travelling in marked lanes.