Obviously the risk of injury increases with increased speed, but first you have to have the crash.I haven't had a serious crash in over 30 year of driving, yet I have received a few speeding tickets during that same period. I have NEVER been involved in a crash that had any element of excessive or inappropriate speed. In fact, the 2 most recent collisions I was basically stationary! (1 was in a shopping centre car park, the other I was stationary waiting the car in front to do a right turn).
In a disproof of the arguments, there were 2 incidents in recent times. Firstly, top cop Ken Lay was nailed by a speed camera, but wasn't involved in any collisions. And secondly, (former) police minister Cameron was involved in a collision where he wasn't speeding (by his own admission, just not paying attention).
All these arguments for cameras are based on statistics. There is a saying about statistics - "there are lies, damned lies, and there are statistics".
I will admit to having generally slowed down on the roads, but not because I believe the arguments in favour of cameras. I have slowed down because I no longer wish to contribute to the coffers of Victoria.