In normal driving you should only pass other moving vehicles on their right. There are, however, four basic exceptions to this rule.

	If the vehicle in front is signalling to turn right and you can pass safely to the left without entering a bus lane during its period of operation
	If you are turning left in a lane specifically designated for left turning traffic.
	If traffic is moving slowly in queues and your queue is moving faster than the queue to your right - Note: you should not change lanes to the left simply to overtake in this situation
	In one-way streets where vehicles may pass on either side

In any of the situations listed above, you must take special care. 

The driver that you are passing may not be aware of your presence. Always be ready to give way to drivers who may move to the left, in front of you, without warning!