Top speed 156mph

[Janik]

Top speed 156mph

WOM wrote: b) you'd be much better off if you'd do as they do.

Ah, no. Not unilaterally. We are worse off if you act unilaterally. That is my point here.

If you can affect a general change in behaviour, then it's true. But only then.

[WOM]

Top speed 156mph

Again, I think your thinking is flawed. If we all drove the posted limit, accidents would reach a baseline. Maybe 1 death per 100,000 miles driven, say. If we lower the posted limit and all drove the new lower limit, we would expect to (and actually would) see a drop in death to, say, .75 per 100,000 miles driven.

What I think you're saying is that some of us driving the posted limit and some of us driving faster is the cause of higher deaths. ie, it's the differential and not the speed itself. Or, if we all drove the higher speed, we'd see fewer crashes/deaths.

Which is, of course, coocoobananas.

[Janik]

Top speed 156mph

Nope. I would expect fewer collisions in certain circumstances (i.e. Motorways and the like). But more deaths overall, even on those roads.

Back to likelihood vs severity, with severity increasing with increasing speed.

[Janik]

Top speed 156mph

Again, to dial it back to the starting point, I'm also saying that the British driving test is right to penalise people for driving below the speed limit when the conditions would permit reaching that speed.

Basically that the British driving test is not being utopian. It's testing on the world as it actually exists, and is down marking behaviour that will reduce the overall safety levels in practice rather than against an ideal.

Speeding isn't necessarily a major mark and an instant fail, but it could and often will be, rightly enough.

[Glass Half Empty]

Top speed 156mph

Again, I think your thinking is flawed. If we all drove the posted limit, accidents would reach a baseline. Maybe 1 death per 100,000 miles driven, say. If we lower the posted limit and all drove the new lower limit, we would expect to (and actually would) see a drop in death to, say, .75 per 100,000 miles driven.

I'm not sure I wholly agree with this - bear with me as I've probably not thought this fully through but... A consequence of reducing speed limits would be to reduce the capacity of the road system as fewer vehicles would be able to pass any given point within any given unit of time, therefore congestion would increase and journey times would also increase, leading to an increase in driving time. I would expect that if people are spending a longer time driving they will have more accidents.

[Fussbudget]

Top speed 156mph

Glass Half Empty wrote: A consequence of reducing speed limits would be to reduce the capacity of the road system as fewer vehicles would be able to pass any given point within any given unit of time, therefore congestion would increase

Not necessarily.

[Glass Half Empty]

Top speed 156mph

Ok so not so logical then, but surely any "accordion effect" must come as a result of speed differentials not speed per se.

[WOM]

Top speed 156mph

Exactly. The faster you go, the more space you leave between vehicles. Hence, lower speeds actually increases capacity.

However, that not being either the goal or a likely side effect, it would simply moderate the accordion effect.

[Janik]

Top speed 156mph

Some thoughts on traffic jam physics, which give jumping off points of possible causes for the "accordion effect".
http://www.smartmotorist.com/traffic-and-safety-guideline/traffic-jams.html

One thing that is implicit, but not mentioned on his 'Merging-lane Traffic Jams, A Simple Cure' is that a good proportion of queue jumpers who go shooting down the empty lane help ease congestion. They exploit the 'gaps' left by considerate motorists, and pack the cars into the space better. Absolutely the worst thing drivers can do is merge before the merge point. That simply extends the length of the shut lane! Obvious if you think about it, but against all ingrained British principles of queuing and fairness.
From the Federal Highways Agency:- http://ops.fhwa.dot.gov/publications/fhwahop12012/sec2.htm#sec24
(am I going to highlight this line It is repeatedly shown that traffic is inherently safer when all vehicles are traveling at or near the same speed. - ah, go on, then.)

There is also this, which feels like diametrically the opposite effect, on escalators.

[Janik]

Top speed 156mph

I guess I should note that the Federal Highways Agency must be using the word 'safer' in a slightly different meaning to me.

A stream of traffic all moving with speeds within 1% of each other at 55mph is clearly safer than the same 1% variation at 60mph. However if the average speed is the same of two distributions, then the one with a lower the standard deviation is the safer the situation.

WOM wrote:

Mostly I'm bucking against the idea that slowing down automatically make things safer, and is therefore a straightforward answer. Unless you can get everyone to do it, it doesn't.

But slowing down automatically makes things safer. It's been studied for decades and has been proved beyond a shadow of a doubt. I guess the question is, why are you bucking against it? Do you suspect some shadowy 'drive slower' cabal is promoting it to make money? The point of speed limits is - specifically - to get everyone to do it.

I've remember my argument now, having got lost in the woods last night.

It runs like this:-
Everyone slowing down makes things safer. This is what has been studied for decades and proved to be the case.
Some people slowing down to take the moral lead makes things more dangerous. This has also been long studied and repeatedly shown.

So the person looking to increase everyone's safety should speed up/maintain speed in the short term, and campaign for lower speed limits in the long.

[Evariste Euler Gauss]

Top speed 156mph

http://www.bbc.co.uk/news/uk-england-sussex-35667449

54 in a 30, what an absolute wanker.

Really disappointing when people whose work you hugely enjoy and admire turn out to have feet of clay.

[WOM]

Top speed 156mph

Janik wrote: Some people slowing down to take the moral lead makes things more dangerous. This has also been long studied and repeatedly shown.

I'd like to see the science on this one. Surely you're referring to people who drive beneath the speed limit / absurdly slow for the situation. Because I can't imagine a scenario whereby someone travelling the posted limit is considered (or measurably even) a danger to those speeding around him. The presumption is that people travel the posted limit or below a threshold of 15% above it. How are these people considered a danger to one another?

The overall point, though, is to lower the threshold and see a commensurate reduction in accidents and deaths. And the decline isn't linear either.

[anton pulisov]

Top speed 156mph

The Autobahn is ridiculously dangerous, especially the two lane stretches with no speed limit. It makes no sense. When you only have two lanes, you have trucks doing 80-90 km/hr in the right lane and you have maniacs doing anywhere between 160 and 220 km/hr in the left lane. The speed differential is huge. Any car driver wanting to overtake a truck is looking at trying to judge the speed of distant specks in the rearview mirror. And if a driver pulls out to overtake and gets rammed from behind by a Merc doing 220 km/hr (because the overtaking driver mistakenly judged the Merc to be doing, say, 140 km/hr), the German police are likely going to be equally critical of both drivers.

All other motorway systems in western Europe have a lower fatality rate than the Autobahn, but point this out to a German and they will come up with a ridiculous explanation such as, "there is a lot of traffic in Germany."

Whenever I cross the border and leave Germany I immediately feel much calmer. Germans tell me it's because I don't drive on the Autobahn enough, but I drive there regularly. I have no problems with it and am able to cope. I just find the whole thing unnecessarily dangerous. Maybe it's the other way around, maybe they don't drive on normal motorways enough to appreciate the increased safety.

Of course, the politicians know it is dangerous not having a speed limit, but you won't get elected in Germany by promising to introduce a speed limit.

[Evariste Euler Gauss]

Top speed 156mph

A good friend of mine, US guy name of Andrew Tauber who's now a lawyer but used to be a journalist, did a very nice little piece in the Economist in the early '90s comparing the US populace's sense of entitlement to carry lethal fireams with the Germans' sense of entitlement to drive at lethal speed.

[Janik]

Top speed 156mph

WOM wrote:

Some people slowing down to take the moral lead makes things more dangerous. This has also been long studied and repeatedly shown.

I'd like to see the science on this one. Surely you're referring to people who drive beneath the speed limit / absurdly slow for the situation. Because I can't imagine a scenario whereby someone travelling the posted limit is considered (or measurably even) a danger to those speeding around him. The presumption is that people travel the posted limit or below a threshold of 15% above it. How are these people considered a danger to one another?

Well, there is this dating from back in 1964. That seems to have been the first attempt to perform this kind of research:-



The literature review section of this article provides a pretty good summary. The Soloman research that the above graph comes from, and subsequent studies that replicated it, are quite strongly criticised. However other, better studies have also shown a distribution which has 15.5 mph in relation to the median speed.

Of course, I repeat the stuff of a number of pages ago on the risk matrix. These studies are all talking about collisions. Their evidence says relative speed is a good indicator of the likelihood of a collision, both for drivers above AND below the median. But the associated risk from lower speed collisions is not as large as high speed collisions due to the greater consequences.

So argue for the lower speed limits. But in the meantime go with the traffic flow. That is why this tends to be the attitude of national driving tests and some road safety campaigns (those that will allow nuance into their world, at least).

[Fussbudget]

Top speed 156mph

I'm not sure the argument is so much for lower speed limits, as for better enforcement of the existing ones.

[anton pulisov]

Top speed 156mph

Evariste Euler Gauss wrote: A good friend of mine, US guy name of Andrew Tauber who's now a lawyer but used to be a journalist, did a very nice little piece in the Economist in the early '90s comparing the US populace's sense of entitlement to carry lethal fireams with the Germans' sense of entitlement to drive at lethal speed.

It's a good comparison, I think I mentioned something similar on here before. You often meet very well educated Germans who seem to have a blind spot (pun perhaps intended) in their brain when it comes to the dangers of speeding.

It's simple really. Accidents are gonna happen and F=ma. The faster you are going, the more the damage there is going to be.

[anton pulisov]

Top speed 156mph

Janik wrote: So argue for the lower speed limits. But in the meantime go with the traffic flow. That is why this tends to be the attitude of national driving tests and some road safety campaigns (those that will allow nuance into their world, at least).

Indeed, to reduce the chances of collision there should be more uniform speed. So there needs to be a maximum and minimum speed limit. There is a minimum speed limit of 70 km/hr on Dutch motorways for this reason.

The autobahn is ridiculous because there is no maximum speed limit on a road that is used by trucks and buses which are going along at 90 km/hr. Then you have people in fast cars overtaking at 180 km/hr. The speed differential there is 60 mph. It goes off the scale on the graph you posted.

[Janik]

Top speed 156mph

antoine polus wrote:

A good friend of mine, US guy name of Andrew Tauber who's now a lawyer but used to be a journalist, did a very nice little piece in the Economist in the early '90s comparing the US populace's sense of entitlement to carry lethal fireams with the Germans' sense of entitlement to drive at lethal speed.

It's a good comparison, I think I mentioned something similar on here before. You often meet very well educated Germans who seem to have a blind spot (pun perhaps intended) in their brain when it comes to the dangers of speeding.

It's simple really. Accidents are gonna happen and F=ma. The faster you are going, the more the damage there is going to be.

And K = 1/2 m v²
So exponentially worse with increased speed.

[Kevin S]

Top speed 156mph

antoine polus wrote: Accidents are gonna happen and F=ma. The faster you are going, the more the damage there is going to be.

'a' in this formula is acceleration and not velocity.

[Janik]

Top speed 156mph

If one comes to a sudden standstill from 60 mph the acceleration is necessarily greater than if one does so from 45 mph. So its still relevant to the situation.

Fussbudget wrote: I'm not sure the argument is so much for lower speed limits, as for better enforcement of the existing ones.

The argument is for both, isn't it?
Stage 1 - police the current rules properly and get people used to that being the case
Stage 2 - reduce the limits where politically possible

WOM is unquestionably right in his basic point that speed kills, and reducing average speeds would save lives.

[Evariste Euler Gauss]

Top speed 156mph

So exponentially worse with increased speed.

Errm, quadratically actually. But hey, you're very patient and polite with my daft comments and questions on tennis, so I won't go off on one! [insert smiley]