As I said, the posts to this thread are a good example - the bridge crashes are due to stupid drivers, for example. Might be true. Might not. No-one knows.
I have to say that I'd need some very convincing evidence before I contemplated any other reason. Measure load, see sign, don't go - it doesn't get any simpler.
On the subject of road toll, it's one of my pet beefs that Licences are far too easy to get. Driving must be the only discipline in which the incompetent are allowed to teach the innocent. The instructor's bad habits are learnt by the pupil and so it goes on.
The kid sees and hears dad abusing other road users and blaring the horn and learns that selfishness and impatience are the norm.
Then we see mummy teaching little Jane to drive - in the big SUV at 90 km/h in the extreme right lane of a freeway ( don't laugh; I see it often enough) and little Jane learns to stay as far to the right as possible and go slowly whilst ignoring the signs that say "Keep left unless overtaking." I have actually had a conversation with one such driver who admitted quite candidly that she can't drive in any other lane; that's how she was taught.
In short, the bad habits are passed on from generation to generation. Any official solution is well buried in the Too Hard basket.
On top of this, we are burdened with this "speed kills" nonsense. It's not speed that kills; it's driver incompetence that kills. Notwithstanding this, the official version is that if you stick to speed limits everything will be OK. To emphasize this, we put speed cameras ( sorry; "Road Safety Cameras") all over the place and ping people for being 5 km/h over the limit. Increased safety nil, angry motorists 1. Worse, many believe that all they have to worry about is the speed limit, to the detriment of everything else they should be aware of.
I exempt the 40 km/h school zone limit from criticism, due entirely to the unpredictability of kids. Enforce limits where they're vital, and ignore them where they're not.
Hoons, alcohol, drugs, and distractions like phones, GPS etc are another kettle of fish altogether.
As Historian has pointed out, we have safer cars, compulsory seat belts et al, but the problem is that these are all based upon the belief that you will crash. You're not taught how to avoid crashing.
Unfortunately, my gloomy conclusion is that it will never get better until there are radical changes in driver education and licensing. I'm not hanging by my thumbs, waiting.