[Martin Taylor 2007.04.14.22.40]
[From Bill Powers (2007.04.10.0530 MDT)]
Rick Marken (2007.04.09.1630) --
[Gary Cziko] It appears that people are controlling for a certain degree of safety. So by making the environment a bit less predictable and appear a bit less safe,
drivers slow down and actually make it safer.
So is he saying that you control better for safety without the safety
rules? If so, I'd like to see the evidence for that. My guess is that
safety rules (properly implemented) would improve the feedback
connection between yourself and getting hit by cars (or staying
unhurt if you do get hit). So safety should improve with properly
implemented safety measures. If it doesn't, then the safety department
is probably being run by a libertarian, which is like having the
government run by anti-government conservatives, and you can see how
well _that_ works;-)
I share your skepticism. Control theory would not predict this outcome on the basis of the properties of a single control system. Increasing disturbances or reducing loop gain will lead to more error, not less. Perhaps a multileveled model would suggest a way to believe this proposition, but I'd have to see it (and test it).
It's funny, but I was recalling this Dutch "experiment" when I was driving on an expressway in Victoria State, Australia, last week. I felt it was the most dangerous highway I had ever been on. In Victoria, they enforce the speed limit VERY strictly, and on this six-lane motorway, the speed limit was 100 kph. Almost every car was going within 1 or 2 kph of the limit.
Although I was driving the highway on Easter Friday and Sunday, with very light traffic, I have never felt so nervous. Why? Subjectively, there were three reasons, two of which apply to the more general case.
1. The traffic pattern changed VERY slowly. If I was beside a car, it might take minutes to get past it, or I would have to brake to get behind it to change lanes. Because of the severe enforcement, reminded frequently by signs like "Speeding -- sever fines and loss of licence", I would not dare accelerate to 105 kph. So it would be very hard safely to take emergency action if required. One would need a lot of notice that the emergency would soon appear.
2. Related to the above, in the traffic patterns, NOTHING HAPPENS, except that people join and leave the motorway at interchanges. One is lulled into a false sense of security. Being aware of this (see other thread between Bill and Elizabeth), I tried to be especially attentive, but it's so easy to allow one's attention to wander away from the traffic and to think of other things. On a normal highway, this hardly ever happens.
3. Specific to the multi-lane highway situation: There is VERY poor lane discipline when the speed limit is so rigidly controlled, despite a multitude of signs that say "Keep left unless passing". But if one is driving 99 kph, one feels entitled to use any lane, as nobody should be expected to pass. Nobody can go more tha 100, and most drivers to give their speedometers credit for 1 kph of error (and the highway has places with radar that shows your actual speed, so they know, pretty well, what their speed is.
Paradoxically, or perhaps not, I have always felt safer on an autobahn with no speed limits, at about 170 kph than at home where the speed limit is 100, but most drivers go between 110 and 130; and I feel much safer at home than on that highway in Australia. I'd hate to drive that road in heavy traffic!
...
Obviously, if installing some purported safety device is followed by an increase in the accident rate, AND removing the safety device is followed by a decrease in the accident rate, we can reasonably conclude that something about the design or placement of this device leads to more accidents. Perhaps it is demanding too much attention from the drivers, like a road sign containing 100 words.
Or it removes the need to pay attention. Although "boring" isn't commonly used in a PCT context, it can be important. Think of the Nullabor highwayin South Australia, with 150 km streatches of dead straight rod on one side of a railway line, terminated by a switch to the other side of the line and a ile of wrecked cars. Or, think of the old (1940's to 60's) studies of "vigilance" in which signals that are theoretically very easy to see are completely missed when the person has been watching for more than a few minutes and there have been very few actual signals.
Maybe the "attention" thread might be augmented by some discussion on the PCT-relevant meaning of boredom. It's a real enough experience, when one seems not to have enough consciously aware controlling to do. And I think it relates to the question of whether highways can be too highly controlled -- excess safety precautions apparently making for more danger. It also my relate to the question of whether we do actually control for a certain level of risk, as sometimes is suggested.
My personal view on speed limits is that there is sometimes a need for them, but only in cases where there is a danger that is not obvious to the driver unfamiliar with the road. On severely winding roads in New Zealand, I found the speed cautions on the curves very useful, as they allowed me to judge what kind of a curve lay beyond the part of the road I could see. They weren't speed limts, but I think there would have been justification to make them so. Otherwise, I think mandatory speed limits tend to make people think that the limit speed is safe, when it often isn't. They use the speed limit to set their reference level for driving speed, rather than using their perception of the road conditions.
CSGnet is seldom boring!
Martin