Ever notice when they stick a camera up at a set of lights, it always faces the direction with the increased change in speed limit? Never any of the other 3 directions.
Take Sturt Rd/Marion Rd for instance. A majority of the vehicle crashes actually occur in the direction not captured by the camera (east-west).
Another famous one is the one crossing on West Tce. Funny how they changed speed limit signs at that intersection to catch people out. 2002, revenue from speed cameras fell by $2M, so what did they do? They introduced the 50kph limit in "built up areas". Our streets were getting safer, its what they CLAIMED they wanted, but then they change the rules and make us all crims for driving at 60! And it made them look good on paper to the Govt to spend more money on trying to catch the law breakers that THEY created!
EDIT: I rarely get caught for speeding .. maybe once every two years for 3-5kph over, so I'm not ranting because I'm sore about getting caught. I'm ranting because it is clearly revenue raising and they think we are stupid.
If we ALL drove at 50 and their revenue went down, they'd just lower other limits all over SA, maybe even lower 50 to 40! Some day in the next 5 years, it might take us days to travel interstate with the speed limit being 80kph, or 70kph even.