When can you legally pass on the right?

Answer 1

IN COUNTRIES WHERE THEY DRIVE ON THE RIGHT:

When there are three or more lanes of traffic going the same direction it is usually considered legal to pass on the right. Also, when the car to the left is making a left turn and you have a lane to pass. IN COUNTRIES WHERE THEY DRIVE ON THE LEFT: ... it is normal to pass on the right.

In such situations, such as in the UK, the rules for overtaking on the left are:

* only overtake on the left if the vehicle in front is signalling to turn right, and there is room to do so * stay in your lane if traffic is moving slowly in queues. If the queue on your right is moving more slowly than you are, you may pass on the left. * On motorways, ... in congested conditions, where adjacent lanes of traffic are moving at similar speeds, traffic in left-hand lanes may sometimes be moving faster than traffic to the right. In these conditions you may keep up with the traffic in your lane even if this means passing traffic in the lane to your right.