Well, in short, my point was that in the absence of a speed limit (or where the speed limit is utterly unattainable) 90% of drivers do select a safe speed for the conditions (vehicle, other traffic and weather) unprompted. All setting unreasonably low limits achieves is:-

1) Bringing the law into disrepute. Isn't that an offence in itself, at least under UK law?

2) Given sufficiently advanced detection technology, raising revenue from people who's only offence is driving at a safe speed but above an arbitrarily set figure.

OK, over-eager to grind my own axe I may have interpreted faboka and Mute unfairly, apologies for that.

I agree with ScoobyChris that the hen/egg problem is present here and that speed limits can be misinterpreted as "safe speed during any condition". However, the same problem arise with every technical gadget. ABS and EPS can make you over-confident and falsely convince you that electronics will take care of every stupid mistake you make. This, of course, is no reason to stop putting these things intor our cars, and most drivers steer clear of the trap.

That 90 % of the drivers select a safe speed regardless of formal limits is perhaps an exaggeration (80 %?) but in principle Ken's probably right. And for the rest the prospect of fines/points may serve as a restriction. Today drivers may add 10 mph to the limit. But if there were no limits, how fast would they drive?

It might well be that nothing much will change if limits were abandoned. But it's also possible that we will have more fatalities and severe injuries. Are we willing to pay for that experiment?

The 90th Percentile rule is actually pretty well documented; try starting at www.abd.co.uk (may be www.abd.org.uk . I don't fully endorse their views, but they're frequently a good place to start for finding genuinely non-politically controlled research on road safety.

The 90th Percentile rule is actually pretty well documented; try starting at www.abd.co.uk (may be www.abd.org.uk . I don't fully endorse their views, but they're frequently a good place to start for finding genuinely non-politically controlled research on road safety.

Thanks for the link Interesting reading. Full address to relevant site is http://www.abd.org.uk/speed_limits_85th.htm

If I understand the reasoning correctly it means that with no speed limits drivers' different choice of speed will be arranged in the well-known Bell curve pattern (or Gauss curve). Also, accident risk rises sharply at speeds above the 90th percentile, as showed in the diagram (that also shows that extremely low speed is hazarduous):

Consequently, a good rule of thumb is to set speed limit at the 85 - 90 % mark.

The question that arises is: When a speed limit is introduced, what are the conseqences? Will 10 % of the drivers still drive too fast? Fewer (fearing fines)? More? Another possible result is that some (less experienced) drivers that previously drove slower now increase their speed to a level they don't really master, since the signs (falsely) implies that 60 mph is a "safe" speed.

BTW, the strategy mentioned of using "count-down boards" as a warning to drivers of the speed limit ahead (instead of extending a village speed limit for considerable distance in open countryside) has recently been adopted here in Sweden.

I think it's too hard to try and guage safety / crash incidents by only looking at speed. Its neglects the other, more important factor in the equation, space. Just as it's a much harder task to have a crash without a difference in speed between 2 bodies (you'd need to change the course of the bodies to crash them if they both travelled the same speed), it's altogether *impossible* to have a crash without a space differential. Removing the space difference is the crash.

But, i think that's exactly what we've tried to do for too long. Borne out by the fact that (fatal) crashes do occur, well within the speed limits, maybe even most crashes occur within applicable speed limits (i've not checked). Focusing only on speed does not solve the safety problem, but it does bring along a lot of baggage and inconvenience -- it's not a "free" attempted solution it has costs.

We can approach things in a safer way while removing the baggage (lower throughput for a given section of road) associated with the speed focus.

Safety has to take priority over making progress, in my mind. But because safety is not an absolute, and is just a trade-off of various factors, i think the factors can be rearranged to:

* Increase safety

* Increase throughput for a given stretch of road

On top of that, there are minimal down sides. The biggest one i can come up with is reduced mobility for persons who cannot achieve the necessary standard.

EDIT: that reads a bit like i'm saying higher speeds automatically mean higher throughput. They dont. I'm not trying to make that point.

Edited 20 May, 201016 yr by Mute

I think when trying to wrap something as complex and varied as driving in statistics, you inevitably come up with very unreliable results.

For example, if I go and stand on a motorway bridge and measure speeds of cars, I'm going to be influence driver behaviour and most likely risk if there's a bit of emergency braking, which will skew the outcome. In fact, a friend who was once responsible for setting speed limits on roads used to use the 90th percentile rule to find the appropriate speed limit. However, discretely recording speeds of cars was night on impossible, especially with 'elf 'n' safety, and so limits continued to be reduced unless she was devious. Likewise, if I am driving along a 40mph limited road at 35mph, chances are most of the people behind me will too. And conversely if I drive at 45mph the same is probably true.

The other thing missing with statistics is driver competence. It may be quite possible for an experienced/highly trained driver to drive along a 60mph road at 150mph safely and with a minimal accident risk. Yet a brand new driver who's just torn up their L-plates will be a significantly higher risk, even driving within the speed limit.

Unfortunately, like all "politically" motivated sites, ABD, Safespeed, Brake. etc all have an agenda :(

Chris

Edited 20 May, 201016 yr by ScoobyChris

[---]

The other thing missing with statistics is driver competence. It may be quite possible for an experienced/highly trained driver to drive along a 60mph road at 150mph safely and with a minimal accident risk.

[---]

Possible, yes, but only during very special circumstances, e.g. a road more or less empty of other vehicles/drivers since you can never (to 100 %) be sure of what they will do. Just as on some streets with lots of kids about, one of them could suddenly jump out in front of your car from behind a hedge so that the only 100 % safe method would be that old solution having a man with a red flag walk in front of you

Driver competence is a tricky thing too, since you can have good and bad days, being tired, having had a row with boss or SWMBO... OK, here one of course could argue that the really competent driver takes such factors into account. Sadly it's only human to do exactly the opposite, letting out aggression and frustration through your right foot. Must confess that I've done it myself a few times (nothing that I'm proud of)

Edited 20 May, 201016 yr by swedishskoda

It may be quite possible for an experienced/highly trained driver to drive along a 60mph road at 150mph safely and with a minimal accident risk. Yet a brand new driver who's just torn up their L-plates will be a significantly higher risk, even driving within the speed limit.

Chris

I wouldn't agree with experienced but Highly trained yes.

I was experienced before i did a few driving courses i,ve had to do for work and i was utterly shocked at just how bad a driver i was beforehand. I "thought" i was a "good" driver until i did the courses. Now i know it was more down to luck & modern braking, suspension, chassis setups etc that i didn't crash.

Many people think that because they have been driving for years they are experienced enough to drive at high speed. That is definately not the case. Unless you have been trained to drive at high speed safely then im afraid you can't. Yes some people have natural ability but experience only gives you confidence within your ability. It doesn't raise your ability imho.

I did mean "no limit" but it was more a sarcastic comment. But it added to the debate so I won't withdraw it

So if we did raise the motorway speed to 80 or even 90. On your typical day to day drive would that change anything? For me it's pretty impossible to hit 70 safely. So what would raising it solve?

Edited 20 May, 201016 yr by faboka vrs

I did mean "no limit" but it was more a sarcastic comment. But it added to the debate so I won't withdraw it

So if we did raise the motorway speed to 80 or even 90. On your typical day to day drive would that change anything? For me it's pretty impossible to hit 70 safely. So what would raising it solve?

Raising it to 90 would mean you can make progress on a quiet empty night or day when there is little traffic.

I agree it would make little effect day to day, and the police would still be able to pull somebody doing 90 in heavy traffic, for due care and attention or something.

I maintain if you raise it to 90 however that you must also have the poor weather limit to go with it.

Thanks for the link Interesting reading. Full address to relevant site is http://www.abd.org.uk/speed_limits_85th.htm

If I understand the reasoning correctly it means that with no speed limits drivers' different choice of speed will be arranged in the well-known Bell curve pattern (or Gauss curve). Also, accident risk rises sharply at speeds above the 90th percentile, as showed in the diagram (that also shows that extremely low speed is hazarduous):

Consequently, a good rule of thumb is to set speed limit at the 85 - 90 % mark.

The question that arises is: When a speed limit is introduced, what are the conseqences? Will 10 % of the drivers still drive too fast? Fewer (fearing fines)? More? Another possible result is that some (less experienced) drivers that previously drove slower now increase their speed to a level they don't really master, since the signs (falsely) implies that 60 mph is a "safe" speed.

BTW, the strategy mentioned of using "count-down boards" as a warning to drivers of the speed limit ahead (instead of extending a village speed limit for considerable distance in open countryside) has recently been adopted here in Sweden.

If the 85 percentile speed (rounded) is used as a limit it actually has very little effect on driver behaviour. Equally, if an excessively low limit is set, and there is a low fear of prosecution, that has no effect on most drivers behaviour, but a negative effect on road safety, since the 90+ percentile drivers start making dangerous overtaking moves on those drivers who have dropped their speed to the posted limit.

Ref the use of count-down markers, they can actually expose incompetence. I've followed people who've braked sharply to slow to the posted limit at the outer countdown marker. My point here is not about my delayed journey, but about the incompetence that leads them to not see the board in good time, and to treat the countdown board as the start of the limit which it isn't!

Raising it to 90 would mean you can make progress on a quiet empty night or day when there is little traffic.

I agree it would make little effect day to day, and the police would still be able to pull somebody doing 90 in heavy traffic, for due care and attention or something.

I maintain if you raise it to 90 however that you must also have the poor weather limit to go with it.

Define "poor weather". Is it "when it's raining"? If so, then I've got 2 problems with that:-

1) I've been in conditions when it was raining enough to require wipers, but visibility was unimpared and the road surface was remaining dry.

2) I've been in condiitons when there was bright sublight, but the road surface was very wet.

Is it "when it's misty or foggy"? A quick study of the number of vehicles that pass a stationary observer in an hour with front or rear fogs burning on a clear night in Winter should show up the problem with that.

Is it "when it's snowy or icey"?

Define "poor weather". Is it "when it's raining"? If so, then I've got 2 problems with that:-

1) I've been in conditions when it was raining enough to require wipers, but visibility was unimpared and the road surface was remaining dry.

2) I've been in condiitons when there was bright sublight, but the road surface was very wet.

Is it "when it's misty or foggy"? A quick study of the number of vehicles that pass a stationary observer in an hour with front or rear fogs burning on a clear night in Winter should show up the problem with that.

Is it "when it's snowy or icey"?

Works in Germany, so we just use what they use or only allow the higher limit on roads with the capability for variable speed limit signs.

Edited 21 May, 201016 yr by cheezemonkhai

My point here is not about my delayed journey, but about the incompetence that leads them to not see the board in good time, and to treat the countdown board as the start of the limit which it isn't!

Not to mention the nincompoops that keep a perfectly legal speed but brakes at the sight of a speed camera, apparently 'to be on the safe side'

Not to mention the nincompoops that keep a perfectly legal speed but brakes at the sight of a speed camera, apparently 'to be on the safe side'

How about "brakes sharply for a telecoms company van that was visible from 500m away"? NB, I could see the van despite being behind the braker.