So I called the SA Police today to report an incident. They were extremely helpful and it was a very worthwhile exercise.
In the course of that conversation, they said:
If a vehicle is turning left from one road to another (for example turning from Frome St onto Flinders St, heading south) and pedestrians have not yet started crossing the other road (in this example, Flinders Street) then they must wait to let you turn, provided that you're indicating and otherwise behaving legally. They're not in the road. They can't cut you off by entering the road.
However, cyclists on the left-hand-most part of the road are 'on the road'. Even if you're in your vehicle, indicating, you must wait to let them pass. Cutting them off if illegal. The rules of the road apply.
Furthermore, cutting them off without indicating in an deliberately aggressive manner could potentially constitute assault with a deadly weapon or a similar serious charge.
However, riding along on your bike, if a car is indicating to turn, you may not overtake them on the inside. It's just as illegal. So don't do it.
Please ride safe.
I cannot believe that Derek is right and Aaron wrong.
I too cycle south along Stephens Terrace and believe it is 'driving with undue car' at least when, drivers in the process of overtaking, cut across my path to turn left. A driver is required by law to give sufficient notice of changing lanes and indicate for several seconds. When these vehicles cut across my path, have not been in front of me long enough to give the required indication.
The MUARC recently did a study where cyclists wore helmet cameras. Found that in the majority of bicycle-vehicle incidents, majority of drivers in the wrong, the most common incident was turning left across a cyclist's path, and most drivers did not indicate or indicate long enough.
For what it's worth a commuter cyclist friend sent me this link:
Cars shouldn't overtake to immediately turn left across you but if they are ahead and indicating they appear to have the right of way. As noted earlier, self preservation is a good approach here.