Speed limits are set at the level scientifically determined by experts in engineering to provide safety for the majority of people in a range of conditions. Most of the major roads around Canberra are 80 limit. These roads have frequent braking for lights and intersections, and sections where 2 lanes must merge to become 1. I can confidently say the limit is extremely appropriate.
Putting aside the fact that there has been revision of road speed limits since the 50's, the road toll has also dropped a great deal since the 50's. Perhaps speed limits were relatively too high in the 50's.
Not all vehicles on the road have a raft of safety features. Far from it. When maintenance is neglected, as it so often is, with bald tyres and pads worn flat, any braking advantage of a modern car quickly evaporates.
I don't know the figure for higher speeds or other collisions, but last months motor magazine says that in 3/4 of all nose to tail accidents at <30km/h there is no braking at all.
I think it's a safe assumption that a large proportion of all accidents, at all speeds, occur with zero braking. Drivers just don't pay attention. Increasing the speed limits would only have the effect of giving drivers less time to observe and form a reaction and increasing the speed at which collisions occur.
I don't think it's for the average punter with no background and study of road engineering to be able to say what speed limits should be. Like climate change and brain surgery, I'm happy to defer to expert opinion. I can no better judge what speed limit is appropriate for a given road than I can judge the merits and appropriateness of the engineering in the construction of a new skyscraper.
You are right good sir! it is all hard science! theres no, no politics going on there, is there!
Canberra is a nice city, i go there often but their roads are a bit different to where i live, like you said lots of merging and traffic lights, i would prefer to raise the speed limit on our expressways which have no lights, dual carriageway etc to something half decent like 150 [still a lot lower than many european roads]. Even then, those roads should be able to easily handle 100, depending ofcourse on traffic conditions etc, i very much doubt going at 100 on these roads is more dangerous when theres little traffic i.e at night.
The road toll could have dropped for any number of reasons and have nothing to do with speed, increase in safe driving awareness, changes in licensing, increases in fines, crackdown on drunk driving, IMPROVEMENT in road quality [still shit though, but compare the M5 to old roads and its obvious they are doing something better now] and most imporantly, car safety features.
The majority of accidents have very little to do with going faster than the speed limit, infact there is substantial evidence that suggests going about 10% faster than the speed limit is actually SAFER and yes you are right, some people do not maintain their vehicles correctly, that is going to be true at any speed and they are always going to have a higher chance of crashing, whats your point.
If 3/4 of accidents are occuring at less than 30km than what the fuck is the point in lowering the speed limit? it obviously doesnt effect these types of crashes, its just people following too closely or braking suddenly or losing concentration or whatever, nothing to do with traveling higher than the speed limit.
The last bit is the only thing that makes sense, neither of us are road engineers but that doesnt mean we cant comment and debate on the current situation. The fact is that speed limits are more political than hard science. If the point of speed limits is to save lives why not make a uniform 20kmph speedlimit? after all you said yourself that most accidents occur at less than 30kmph! think of the lives we could save! but that wouldnt be convenient would it? the argument of safety and trying to save lives is a joke.
Speed limits are always going to be political and a balance of human cost vs convenience, in the 50's sombody decided that X amount of lives was acceptable for traveling at Y speed so you can arrive at your destination in an acceptable amount of time, with so many different improvements since then and a huge lowering of the road toll why dont we increase the speed limit on roads than can handle it for increased convenience!
After all, many many other countries do it, they build great roads and have high or no speed limits with a low fatality rate that is obviously acceptable to them, we are such a large country, much larger than most of these other countries and we need to travel in less time than we currently do, so if a higher speed limit works for say germany, why cant we do it here?