arthurdent wrote:
The above <lines on psychological evidence> strikes me as a rather unscientific approach
To me, psychology is a remarkably inexact science, and opinions on such things as 'natural speeds' are suspect. When I was 17, the natural speed of the local roads was 115 mph, the top speed of my Avenger GT motorcar. When I was 18, the natural speed of the local roads was 90mph, the top speed of my 250cc motorbike. When I was 25, the natural speed of the M56 was 106mph, the top speed of my Ford escort. When I was 26, the natural speed of the German Autobahns was 125 mph, the top speed of my 1000cc BMW. It may have been the death of my parents that made me think, but in any case, shortly afterwards, the 'natural speed' of the roads seemed to be less and less each year, until now I think the speed limits are reasonable or too high in some cases. How can I explain this 'shifting' natural speed? I can't, other than saying that the whole idea is silly and contrived. You could argue that the speed limit is silly and contrived, except that it has the validity of political consensus and the weight of history behind it, so it seems more silly and contrived to scrap it and start over. Better to use it as a starting block and find better methods to fine tune it against the consensus
arthurdent wrote:
Any data, suspect or otherwise, are better than none at all
I'd make an exception for shaky, psychological stuff.
arthurdent wrote:
Data that may ultimately save lives should be sought with vigour, don't you agree? The assumption that certain data are irrelevant because they are not available defies logic.
I'm trying to be logical but ideas about hollywood-style conversations and natural speeds just don't cut it with me either! Your search for the global minimum could be valid, but we have no test-tube to fine tune that. That is why I am in favour of using it as a starting block and find better methods to fine tune it. Nothing is cast in stone, but I really don't think that scrapping it would be good, not would ignoring violations (SafeSpeeds preferred approach), which is a Nelsonian version of the same thing. I am in favour of careful fine turning of the status quo, which I think is getting closer to the minimum for the road system, or would be if people drove 'on protocol' so to speak. How can we do systematic fine tuning of the system when everybody is off-protocol anyway, i.e. speeding and other stupid stuff? You know better than anyone that, to calibrate anything, you need a stable system to compare against. Of course, we could discuss the 'warts and all' political meta-system and include all the mess as it functions. A form of structured anarchy! Oh, let's save it for another day.
arthurdent wrote:
What do you mean by your post, BW? The argument advanced by SS is that the simple accident causation model that does not include driver psychology does not 'make sense', i.e. that this model is 'simpler than is possible' to paraphrase GB's signature. Is your counterargument to this 'we have no data on this so let's carry on with the set of assumptions that do not rely on such data'?
My argument is that psychological data is more
important than the numerical stuff, but it is much less
reliable. It cannot be measured directly, and so cannot be used as an inhibitor on a case by case basis. Speed, on the other hand,
can be and so we should expect it
to be.
arthurdent wrote:
Incidentally I think that the 'black box' transmitters have the potential to clarify considerably the accident causation picture. Provided these are tested on a sufficiently large and representative sample of the driving population, they could reveal the true relationship between 'bending the speed limit' and insurance risk, and hopefully and more importantly - the KSIs. This will be part of the data that we are missing now, I hope
I sincerely hope that they do, although I feel that drivers with lower average speeds will come off with lower risks. I know the 'time and circumstances' arguments are persuasive, but, as well as individual cases, the limits are also a political device to reduce average speeds and increase average safety, and that does not come across on this web site. Only time will tell.