The best explination I've seen about speed limits.

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M19
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Re: The best explination I've seen about speed limits.

Post by M19 »

Bryn666 wrote: Wed Sep 15, 2021 22:38
M19 wrote: Wed Sep 15, 2021 22:26 The A43 Moulton Bypass was designed with a 40mph speed limit as the expectation was that this stretch of new dual carriageway would have development frontage with tree planted verges to create a boulevard. Hence the character of the route would make 40mph self enforcing.

The engineers however have ruined the design. There are no verges. Housing areas are fenced off, the central median is tarmac and there are no verges. The heightened degree of segregation between development and the road that you would normally expect for faster dual carriageways makes the 40mph limit feel like a joke and most i.e. a good 90% will drive it at 50mph, if not faster. This is what happens when engineers dismiss place making efforts and stick rigidly to DMRB in a context where Manual for Streets ought to be applied.
Looking at GSV that has all the hallmarks of 1990s mentality - development not managed properly by the council planning team defaulting to DB32 cul-de-sacs facing away from the boulevard, and also... were they building an urban boulevard or a bypass? It's got no motive, it's just bland crap planning that serves nobody.

The aim is for the A43 to be dualled between Northampton and Kettering. Going by the current thinking it will rely on a linear expansion of development along the whole corridor to achieve it. A line of suburbia to fund a road upgrade.

What happened to improving road corridors without expecting developers to pay for it? The current thinking only results in fudged development routes are overwhelmed with traffic from day one, rather than routes that simply need to be improved to do the job of making traffic move smoothly, unhindered by millions of crap junctions.
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Re: The best explination I've seen about speed limits.

Post by Bryn666 »

M19 wrote: Wed Sep 15, 2021 23:04
Bryn666 wrote: Wed Sep 15, 2021 22:38
M19 wrote: Wed Sep 15, 2021 22:26 The A43 Moulton Bypass was designed with a 40mph speed limit as the expectation was that this stretch of new dual carriageway would have development frontage with tree planted verges to create a boulevard. Hence the character of the route would make 40mph self enforcing.

The engineers however have ruined the design. There are no verges. Housing areas are fenced off, the central median is tarmac and there are no verges. The heightened degree of segregation between development and the road that you would normally expect for faster dual carriageways makes the 40mph limit feel like a joke and most i.e. a good 90% will drive it at 50mph, if not faster. This is what happens when engineers dismiss place making efforts and stick rigidly to DMRB in a context where Manual for Streets ought to be applied.
Looking at GSV that has all the hallmarks of 1990s mentality - development not managed properly by the council planning team defaulting to DB32 cul-de-sacs facing away from the boulevard, and also... were they building an urban boulevard or a bypass? It's got no motive, it's just bland crap planning that serves nobody.

The aim is for the A43 to be dualled between Northampton and Kettering. Going by the current thinking it will rely on a linear expansion of development along the whole corridor to achieve it. A line of suburbia to fund a road upgrade.

What happened to improving road corridors without expecting developers to pay for it? The current thinking only results in fudged development routes are overwhelmed with traffic from day one, rather than routes that simply need to be improved to do the job of making traffic move smoothly, unhindered by millions of crap junctions.
Central Government policy unfortunately. All roads have to create car dependent box shed and copy/paste housing hellscapes to get funding these days - the idea that a road exists to connect two points with minimal interference from development seems to have gone out the window.

Even RIS2 is all about how much box shed it can generate, hence the furore about the Oxcam Expressway, which will probably now never happen.
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Re: The best explination I've seen about speed limits.

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Bryn666 wrote: Wed Sep 15, 2021 22:59
fras wrote: Wed Sep 15, 2021 22:46
Bryn666 wrote: Wed Sep 15, 2021 22:42

I give contemptuous opinions the respect they deserve, it's called free speech.
But it seems to me that everybody's opinions apart from your own are contemptuous.
Quite the opposite, when presented with facts and evidence I will re-evaluate my position. The only people who have an issue are those who hold contemptuous opinions unsupported by valid evidence, and then find themselves called out on it, preferring to cry foul that they are somehow being victimised for posting drivel.

Standards on this forum would be much higher if such nonsense was called out and dealt with. We are supposed to be a society for learning, not tedious axe-grinding by people who should have stayed on places like SafeSpeed and uk.rec.driving.

Need I quote the society mission statement, as it appears a good few people have forgotten it?

We are neither a pro-roads nor an anti-roads site. We have no formal links with motorists' organisations or the road construction industry; neither do we have associations with the environmental lobby or road protestors' groups. Rather, we are interested in the history, geography and structure of the British and Irish road networks. Individual members may of course have views on the politics of the network, and we debate the issues from time to time, but SABRE is not primarily intended as a platform for those with an axe to grind.

These continued, and frankly boring, speed limit threads are nothing but axe grinding and it's always by the same few people. So, no, I won't apologise or be courteous about it.
Can I be permitted to grind an axe about a glaring spelling mistake in a thread title?
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Re: The best explination I've seen about speed limits.

Post by ajuk »

Bryn666 wrote: Wed Sep 15, 2021 21:59 You are still determining road safety based on the behaviour of a minority - "15% of drivers will always speed so we should do away with speed limits" is a nonsense argument.
No because that's just another straw-man argument, I've never made that claim. Also worth noting that on average, the 85th percentile speed is only 15% faster than the mean average.
My opinions are mainly based on real world speed data collected on sites where speed limits have been lowered and the sheer scale of levels of discrepancy I've seen between limits and actual traffic speeds depending on whether or not the limit was set based on engineering recommendations or what Helen Lovejoy thinks it should be.
Bryn666 wrote: Wed Sep 15, 2021 21:59 No one intends to crash their car, but humans are prone to errors of judgement that have catastrophic consequences - misjudge the speed of an approaching vehicle turning right - bang, that's someone with a life changing injury. No one intended it to happen but it did happen. Looking in the rear view mirror for an extended period to tell your two children to stop squabbling, missing the child running out into the road for a football - bang, another life changing injury. Fiddling around with the Sat Nav because there's traffic ahead - bang, into the back of a queue.

All these simple errors of judgement, and thousands more, happen every day. Most days there are no consequences, but the days there are someone is dead or disabled for life. Speed limits are part of a wider methodology to mitigate the consequences of mistakes. I would rather we had mandatory retesting of drivers every time a photocard licence was up for renewal, along with intelligent speed detection so that vehicles either prevent speeding or tell you when you are doing so.
That would just encourage people to sit on their limiters rather than using their judgment to better determine their speed, afterall it's meant to be a limit not a target, for example the other day I was going under 20 on a 40 limit road after a Bristol City game ended and road was suddenly pact full of people, also that's why you have dangerous driving laws etc.
You've just done the same thing, you've alluded to poor driving behaviour but then expect those same people to rigidly obey lower posted limits, your alluding to the same thing the guy in the video is.
If you set rules that actively show people contempt you can't then expect those same people to reciprocate that by rigidly obeying them.
Part of the problem is that the way the limits are being set are in and of themselves what drives up the non-compliance and it's being done by people who simultaneously demand that people obey that law, that doesn't make sense. When speed limits are based on the 85th percentile speed it has an enormously beneficial effect on driver compliance and pedestrian expectation on the speed most traffic will be going.
Slightly related, I campaigned to have a limit near me moved closer to a village, removing the arbitrary buffer zone, I was successful the limit now starts where the village starts, this was a speed survey taken in the village before and after.


Speed limits are important, you need people to take them seriously.
Of course that video explains why deliberate disobedience isn't the only issue.
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Re: The best explination I've seen about speed limits.

Post by ajuk »

Bryn666 wrote: Wed Sep 15, 2021 22:59
fras wrote: Wed Sep 15, 2021 22:46
Bryn666 wrote: Wed Sep 15, 2021 22:42

I give contemptuous opinions the respect they deserve, it's called free speech.
But it seems to me that everybody's opinions apart from your own are contemptuous.
Quite the opposite, when presented with facts and evidence I will re-evaluate my position. The only people who have an issue are those who hold contemptuous opinions unsupported by valid evidence, and then find themselves called out on it, preferring to cry foul that they are somehow being victimised for posting drivel.
So have I, I modified my position after seeing this study.
Turns out their sometimes there is a basis to setting speed limits slightly lower than engineering recommendations, however the lack of a 25mph option in the UK starts to become an issue there.

To clarity my main axe to grind is more down to limits set far below engineering recommendations with complete disregard given to the engineering of the road the 85th percentile or even mean average speed.
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Re: The best explination I've seen about speed limits.

Post by DB617 »

ajuk wrote: Wed Sep 15, 2021 23:17 That would just encourage people to sit on their limiters rather than using their judgment to better determine their speed
This is another one of those tropes that comes up regularly - 'sitting on a limiter instead of using judgment' is called 'driving without due care'. It's an offence. Nothing engineers can do will ever change the fact that a speed limit is a limit, not a target. You're almost defeating your own argument, because if we adopt the view as engineers and planners that drivers have to sit on the limiter, and cannot be trusted to perceive emerging and potential hazards and adjust speed accordingly, we must ensure the limiter tops out at so low a speed that the potential for serious injury or death drops. Hence... 20mph limits. Funny old thing.

I will also point out on the subject of hazard perception and risk management, that the DVSA considers these to be core skills required of all drivers, and they are assessed on all tests for a new class of vehicle. If drivers really are that incapable then we don't have a design problem; rather, we are so obsessed with the God-given right to drive a car that we refuse to tighten the training and competency requirements, which would exclude many drivers who are incapable or unwilling to treat driving as an essential skill which requires all their attention. I would argue that implicit design and other speed-perception-reducing methods that engineers are using today have become more and more necessary due to a 'me me me' attitude of many drivers. Sod the pedestrian, sod the cyclist, sod actually looking up from my phone when I'm doing 30mph in a busy shopping street, nobody else matters. So the restrictions get tighter and tighter, because they are within the remit of engineers and planners, whereas driver standards are a Ministerial problem and thus likely to move at a glacial pace. To propose that we give drivers an inch more rope to hang themselves with at present is beyond ludicrous.
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Re: The best explination I've seen about speed limits.

Post by Debaser »

ajuk wrote: Wed Sep 15, 2021 20:02 OK, you don't trust most drivers to drive sensibly, let's say I accept that to be the true.
Every thread talking about smart motorways accepts this to be true; everyone who fears breaking down in a live lane accepts this to be true. They may go on about dangerous design, but the actual danger they fear is being stationary in LBS1 and having another driver go straight into the back of them. Not a fault of the highway, but drivers (and LBS1 isn't usually the home of Audi drivers) unable to do the simplest task asked of them - drive to the conditions - in this case drive at a speed where one can see hazards in enough time to stop (or take avoiding action).
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Re: The best explination I've seen about speed limits.

Post by 2 Sheds »

ajuk wrote: Wed Sep 15, 2021 23:24
Bryn666 wrote: Wed Sep 15, 2021 22:59
fras wrote: Wed Sep 15, 2021 22:46
But it seems to me that everybody's opinions apart from your own are contemptuous.
Quite the opposite, when presented with facts and evidence I will re-evaluate my position. The only people who have an issue are those who hold contemptuous opinions unsupported by valid evidence, and then find themselves called out on it, preferring to cry foul that they are somehow being victimised for posting drivel.
So have I, I modified my position after seeing this study.
Turns out their sometimes there is a basis to setting speed limits slightly lower than engineering recommendations, however the lack of a 25mph option in the UK starts to become an issue there.

To clarity my main axe to grind is more down to limits set far below engineering recommendations with complete disregard given to the engineering of the road the 85th percentile or even mean average speed.
I have ground this axe before. I often cite Nottinghamshire as an example. Almost every time I drive through the county I discover new/lowered limits, most of which are 'political' and not to do with engineering.

Either there's been a tragic accident (where some idiot has been driving way over the previous limit anyway), and a limit is lowered to show some 'action' by highways;
or there's been a pressure group or 'person of influence' asking for a lower limit;
or there's spare money at the end of the financial year, or there's a target to be met.

I get the impression Nottinghamshire politicians would like all roads to be restricted to 20 mph eventually.

In the absence of cameras or police vehicles I find most professional drivers ignore these limits, which risks debasing the justified ones and therefore could be counter-productive to road safety. .
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Re: The best explination I've seen about speed limits.

Post by LoopyUpholland »

Given his aggressive and largely inappropriate reaction to other posts in this thread, I expect this will raise Bryn666's ire further...

I find most speed limits 20 or 30mph too low these days. No rural road should be limited to anything below 50mph, unless the road is of particular poor quality. I do not accept that speed itself is a cause of accidents, and lowering limits as a result of idiots who failed to properly react to road conditions is unacceptable.

It's quite sad that road engineers come out with all kinds of irrelevant drivel to drive limits downwards.

We should be looking at RAISING limits, not lowering them! Motorways in particular have too low a limit. Are German Autobahnen considered that dangerous?
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Re: The best explination I've seen about speed limits.

Post by fras »

LoopyUpholland wrote: Thu Sep 16, 2021 10:11 Given his aggressive and largely inappropriate reaction to other posts in this thread, I expect this will raise Bryn666's ire further...

I find most speed limits 20 or 30mph too low these days. No rural road should be limited to anything below 50mph, unless the road is of particular poor quality. I do not accept that speed itself is a cause of accidents, and lowering limits as a result of idiots who failed to properly react to road conditions is unacceptable.

It's quite sad that road engineers come out with all kinds of irrelevant drivel to drive limits downwards.

We should be looking at RAISING limits, not lowering them! Motorways in particular have too low a limit. Are German Autobahnen considered that dangerous?
Having driven along quite a few of them, no. However just try driving on an Italian autostrada !
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Re: The best explination I've seen about speed limits.

Post by Bryn666 »

LoopyUpholland wrote: Thu Sep 16, 2021 10:11 Given his aggressive and largely inappropriate reaction to other posts in this thread, I expect this will raise Bryn666's ire further...

I find most speed limits 20 or 30mph too low these days. No rural road should be limited to anything below 50mph, unless the road is of particular poor quality. I do not accept that speed itself is a cause of accidents, and lowering limits as a result of idiots who failed to properly react to road conditions is unacceptable.

It's quite sad that road engineers come out with all kinds of irrelevant drivel to drive limits downwards.

We should be looking at RAISING limits, not lowering them! Motorways in particular have too low a limit. Are German Autobahnen considered that dangerous?
Irrelevant drivel, also known as causation and evidence.

What's your evidence to unilaterally raise speed limits everywhere? Do share your working out, you could become a billionaire if you prove road safety engineers wrong.

I'll wait.

Oh, and for what it's worth, I have raised speed limits where appropriate. The fact this has only been done twice in twelve years though suggests it isn't a very common event thanks to evidence based engineering taking priority.

Presumably SABREs armchair experts are also able to fix plumbing and pressurise gas mains on the basis they use taps and gas ovens every day as well.

Whatever, you're the ones who are in an increasingly irrelevant minority group, the days of the tedious pub bore dictating policy based on what they think they know without any evidence are long since past.
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Re: The best explination I've seen about speed limits.

Post by Chris5156 »

LoopyUpholland wrote: Thu Sep 16, 2021 10:11Motorways in particular have too low a limit. Are German Autobahnen considered that dangerous?
Motorways have the limit they were designed for. If you raise the limit you will be saying it’s safe to go faster than the road was designed for, and whoever signs off on that is liable to be in front of the coroner after the first fatal accident. I wouldn’t like to be the one to put my name to it.

German autobahnen have, IIRC, a worse safety record than UK motorways. Being more like Germany won’t make UK roads safer!
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Re: The best explination I've seen about speed limits.

Post by Rob590 »

I Am Not An Expert, but reading this and other threads a lot seems to come down to differing conceptualizations of what causes accidents.

I'd share Bryn's understanding (I think - correct me if I'm wrong Bryn) that the majority of accidents are caused by otherwise-sound drivers hitting moments of bad luck or bad judgement, and so the goal of road enigeering (as well as driver training, setting of speed limits and other measures) is to reduce the liklihood of bad luck or bad judgements resulting in an accident or a severe accident.

It's not about not-trusting drivers, but accepting the law of big numbers: there were 350 billion miles driven in 2019 in the UK, and still 280 billion a year in 2020, noting the effect of covid-19 in reducing numbers. The point is that even if everyone were an excellent driver, when covering 350 billion (that 350,000,000,000) miles there would still be hundreds of thousands of accidents a year because people are not perfect.

The other view seems to be that the majority of accidents are caused by a minority of bad drivers, and that measures which slow down the majority who driving well are therefore a bad idea/unnecessary. We all know that accident rates are higher among poor or inexperienced drivers, but even if it is, that doesn't stop the many accidents between good drivers caused by the big numbers above outweighing those caused by the minority.
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Re: The best explination I've seen about speed limits.

Post by RichardA35 »

I have now locked this thread following reports of axe grinding and you-bombing.
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