How FPTP Silently Sabotages Fair Union Elections

There seems to be a problem with FPTP voting in that “most votes wins” is a highly intuitive system for a single-winner election, despite the fact that this can result in a winner who would lose in a two-person run-off against every other candidate.
There is also an assumption that the winner under FPTP is genuinely the most popular, while the winner under IRV (Instant Runoff Voting) is merely a compromise. In reality, this isn't true—the winner in a run-off system is much more likely to be the most popular overall.

This phenomenon occurs because of the spoiler effect: several similar candidates can split the vote, while a very different candidate, disliked by the majority, can win by appealing to a large enough minority. Under FPTP, the winner could easily be someone who would lose in a two-person run-off against any other candidate.

The flaws of FPTP are particularly problematic in union elections, where there is no polling data showing who is likely to win and people don’t always see the final results.
It would not surprise me that it’s not entirely uncommon for the vote to be so highly fragmented that the selection of the winner could be considered arbitrary.

Why such a flawed system persists, despite better alternatives, I can only attribute to its simplicity and intuitive appeal.
Allowing people to rank candidates in order of preference and selecting a winner by IRV would mean the winner is never arbitrary and is someone who always has a broad range of support from across the electorate.

3 Fallacies

 3 Fallacies I propose. 

Kitten Stomper
The Kitten Stomper Fallacy refers to a rhetorical device or argumentative approach where the speaker asserts the efficiency or effectiveness of a concept, idea, or device without regard for ethical considerations, practicality, or market viability. The term originates from a satirical example where inventors claim 100% efficiency at killing kittens with a device, highlighting the absurdity of prioritizing efficacy without ethical or real-world constraints.


Psychological Denialism.
Psychological Denialism refers to a cognitive bias or argumentative stance where an individual dismisses or downplays well-established principles and observations related to real-world human behavior. This denial often involves avoiding acknowledgment of psychological phenomena, tendencies, or motivations, hindering a comprehensive understanding of human actions and reactions.

Gorilla in the Mirror Syndrome.
Gorilla in the Mirror Syndrome refers to a cognitive bias or communication pattern where an individual, in the course of disagreement or discussion, assumes that those holding differing opinions harbor nefarious motives or intentions. This syndrome involves a tendency to attack perceived motives with vigor, overlooking nuances in the opposing perspective and hindering constructive dialogue due to an unfounded assumption of ill intent. The term is metaphorically derived from the behavior of gorillas, who, when confronted with their own reflection, may become defensive and attack without recognizing that the image is themselves, symbolizing a failure to appreciate the true nature of differing viewpoints

Unintended Consequences: Examining the Safety Risks of Wales's New 20mph Rule

With the recent implementation of the law setting 20 mph as the default urban speed limit in Wales, I assumed that many higher standard and main roads would still maintain a speed limit of 30 mph.

I have previously highlighted evidence suggesting that 20 mph limits can be effective on roads naturally suited for lower speeds, as setting limits slightly below engineering recommendations can enhance safety.  20 mph limits on specific sections of higher standard and main roads, like implementing part-time limits outside schools, can also be an option. However, it's crucial that these exceptions remain just that—exceptions—so that motorists take them seriously.

Regrettably, the regulations governing exemptions to the new rule are poorly thought out and far more restrictive than my initial expectations. If there are houses lining the road it has to be 20 even if the houses along the road are ribbon development.

The old guidelines stated "20mph speed limits should only be used for individual roads or for a small network of roads. Research indicates that 20mph speed limits should only be used where mean vehicle speeds are 24mph or below or where traffic calming measures are planned as part of the speed management strategy".
The new guidelines state "Decisions on exceptions should not be influenced by existing traffic speeds." Notice the lack of the word 'research' in the second one.


Local authorities are now compelled to include higher standard main roads without considering levels of compliance, traffic speeds or engineering recommendations.
This approach not only undermines the significance of speed limits but also calls into question the broader importance of adhering to the law. It is difficult to comprehend how including such high standard roads aligns with the goal of making exceeding the speed limit less socially acceptable.
People will are likely to see the limit as wrong, irrelevant or even vacuous, and that attitude will carry over to places where a 20mph limit is more justified.

Considering traffic speeds is a well-established practice in the decision-making process. If there's an academic study supporting the approach of completely ignoring them, I would appreciate anyone sharing the link in the comments. I've submitted a Freedom of Information (FOI) request to the Welsh government, specifically asking for evidence supporting this approach. However, their response stated that they 'do not have this information.'

Monmouthshire made the decision to lower the speed limit and subsequently imposed a 20mph restriction on the entire B4245 that passes through Magor, Rogiet, and Caldicot.
Both the sections through Rogiet and the Caldicot bypass showed levels of non-compliance of 99%!
The average speed is now 12mph over the limit and the 85th percentile speed is 39mph.
Despite this, only the bypass will have its speed limit raised back to 30 mph. Both roads appear more suited for 40 mph limits, and I believe the bypass was originally designed for 40mph.
Previously, both roads already had a 97% non-compliance rate with the 30mph limit. Instead of raising the speed limit, it was lowered even further.
I asked Monmouthshire council why the road through through Rogiet won't also be made exempt, the claimed that it can't be. They also claimed that "changing motorists behaviour/mindsets will take some time". 

This decision appears to overlook the historical context of why the previous 20 mph limit was abandoned in 1930. Furthermore, it comes despite the high levels of non-compliance with the existing 30 mph limit, which was well established on that road.
The notion that people just need 'time to get used to it' fails to recognize that most drivers are already focused on avoiding accidents and ensuring the safety of others. It presupposes that the speed limit functions because people become accustomed to it, rather than existing to identify reckless drivers. There's also an assumption that individuals who drive too fast for the conditions do so because the limit allows them or due to a lack of signage instructing them otherwise.
Moreover, there's an underlying assumption that setting rules with an air of contempt will be reciprocated with respect. The concern here is that a significant number of vocal advocates for this change seem to assume that the majority of drivers don't accurately assess their speed and further assume that these drivers will improve their behaviour solely due to a change in signage

I initially assumed that the implementation would include the use of repeaters. However, under the new rules, all repeaters on current 20 mph roads are set to be removed. The updated regulations state that the limit will be 20 mph wherever there are street-lights, while 30 mph limits will require repeaters.
In contrast, in the rest of the UK, 30 mph repeaters on roads with street-lights are forbidden.
This disparity between Wales and the rest of the UK creates a conflict in the systems, likely to lead to confusion.

From my observations in other parts of Wales, it appears that many high standard main roads, which one would assume should be exempt, are being included in the 20 mph limits. For instance, in Newport, roads like Cardiff Road, with its substantial width and clear design for at least a 30mph limit and Chepstow Road, which had a 40 mph limit until recently, are not being made exceptions.
In Cardiff, the situation is even more remarkable, as they have included some roads that would be allowed to be made exceptions.

And here lies the predicament: the new guidelines prohibit local authorities from taking into account average speeds, levels of compliance, or engineering recommendations when establishing speed limits. It appears as if the assumption is that there was never a valid reason to consider these factors in the past.

All too often, both sides of the speed limit debate miss the mark. I've heard opponents of these changes argue about the increase in travel time, but I find this irrelevant when over 90% non-compliance is likely, and free-flowing traffic speeds only decrease by 1-2 mph.

It's crucial to distinguish between speed limits and actual traffic speeds, and that's the real challenge for most people. Traffic speeds are primarily influenced by road design and conditions at the time, not by speed limits. This phenomenon stems from how our brains process information and respond to the driving environment, rather than a deliberate disregard for the law. Therefore, it's essential to consider traffic speeds when setting speed limits.

However, this conclusion, rooted in real-world human behaviour and traffic dynamics, often faces opposition from proponents of lower speed limits, especially in areas advocating for 20 mph limits. It seems that concerns are dismissed regardless of the level of non-compliance or if the average speed exceeds the limit. This dismissal can hinder addressing the root issue, which is the need for improved road design to ensure safer and more efficient traffic flow.

I tried to send a Cardiff councillor Dan De'Ath a link to a video from a road safety organisation on the importance of taking account of real world human behaviour in the setting of speed limits and this is what happened. I he just bocked me, this is argument from ignorance as it's finest.

What's perplexing about this approach is its lack of evidence. There seems to be an assumption that speed limits are something you can set and expect everyone to follow, rather than viewing them as a legal tool to identify reckless drivers. However, there's a significant contingent of people who expect or want them to function in that manner. The problem is, even if you try, they don't. I'm not saying you have to like it.

If non-compliance rates are reaching up to 99%, with over 90% being the new normal, it raises a critical question: what am I missing here? This approach not only poses dangers by normalizing speeding and making it socially acceptable but is also insidious because its proponents claim to want the opposite.

Speed limits are designed to assume ideal conditions; hence, we have other laws such as reckless, dangerous, and careless driving. No one can cause harm at an unsafe speed and use 'I wasn't speeding' as a defence.

Driving significantly slower than the majority of other traffic, causing a tailback, is normally a violation of rule 169 of the highway code and is considered a major fault on a driving test. There's a good reason for this.
Individuals attempting to strictly adhere to the speed limit inadvertently increase their risk of accidents by driving much slower than the flow of traffic. This slower pace can lead to traffic bunching up behind them, introducing distractions and potential hazards on the road.

I encounter a challenge when attempting to delve into great detail to offer a comprehensive explanation of the myriad factors contributing to speed limit non-compliance, particularly when these limits don't align with road engineering. For some individuals, no matter how effectively I articulate these reasons and highlight the exacerbating factors, real-world human behaviour is often met with hasty generalization, appeal to motive, appeal to the law, ad hominem, appeal to the stone, and Bulverism.
This makes engaging in a nuanced discussion about the complexities of traffic behaviour and road safety very challenging.

There is a common belief that if you set the limit lower, people who drive too fast only exceed the posted limit by 5 or 10 mph. I have seen three different councillors make this claim, I normally retort by asking them if that's how they drive or if they could drive safely if their speedo were to brake.
According to DfT Circular Roads 1/80 "It is a common but mistaken belief that drivers allow themselves a set margin over the prevailing speed limit, and that if a limit is raised by 10 mph, they will travel 10 mph faster. In fact, an increase in an unrealistic speed limit rarely brings an increase in traffic speeds.
It is much more likely that there will be no change, or even a fall. It seems that drivers relieved of the frustrations of too low a limit rarely abuse the higher one."
I've seen plenty of more recent data that backs up this and I wrote about it previous.
So, not only is it untrue, the reality is the opposite when the limit is set artificially low.

Far from limits targeting unsafe drivers more effectively, this approach prohibits the behaviour of some of the safest drivers on the road and forces the police to focus on them.
This comes at the expense of addressing the behaviour of motorists who are not only the least likely to slow down when limits are lowered but also the most likely to cause harm.
Moreover, these laws may exist to shift responsibility, as when almost all motorists exceed the speed limit, every accident becomes the driver's fault, and the government is no longer held responsible for poor road design or maintenance.
This is before I even address issues such as vulnerable road users such as pedestrians and cyclists having false expectations of actual traffic speeds, satellite navigation systems no longer considering main roads as faster and people overtaking.

If you complain about this, the assumption seems to be you must be some kind of uncaring petrol head. Nope, I understand how speed limits are meant to function, I genuinely think it's dangerous.
If you really want to make the roads safer you need to spend money on changing the design of the road, and for arterial roads you need to provide safe places for people to cross and be sure pedestrians know realistically what speed traffic is likely to be going.

Do you think you need to prohibit your own behaviour?

Once, the emphasis on responsible driving prevailed over rigid adherence to speed limits. Exceeding the speed limit was reserved for reckless drivers. The term "speeding" implied high speeds and risky behaviour.

In a blog post by Mark McArthur-Christie, he asks “What happens if your speedo breaks”?
If you're speedo breaks and you're forced to concentrate on the road and drive at a speed you feel comfortable driving under the prevailing conditions, could you drive safely?
It's an excellent question to ask people campaigning for very low speed limits because they normally are forced into a corner where they have to say "no".
If you don't think you were capable of judging your speed appropriately for however many years, you shouldn't have been driving in the first place.

That doesn't seem to matter to them because some are openly admitting that they are prohibiting their own driving behaviour.
It's one thing for someone to say their behaviour is a bit wrong, it's another to say it should literally be illegal. Imagine something being so wrong you need to make it illegal, but before you do so, you film yourself doing it.

It's a further step then admitting that you need to use technology to make sure you don't accidentally break a law you introduced. Not only does the law show contempt for other people, but they have to feign a self-contempt for their previous driving behaviour to justify it.

He's right that in Cardiff you do need a limiter to not break the speed limit, that or you need to be concentrating on your speedo as driving at the speed limit on many of the roads is now counter-intuitive.
I'd like to think someone who has likely been driving longer than I have and is also a councillor should already have been driving "safely".
I'm not sure if driving significantly slower than the mean speed of traffic does make you safer.

The first point there is that the vast majority of Cardiff's 20 limits are not "zones" a 20mph zone is a road designed to make speeds over 20mph difficult, they're often lined with speed humps and chicanes and don't require repeaters.

For a 20mph (sign only) limit the nature and/or design of the road should mean that speeds much over 20mph are naturally counter-intuitive.
Think of normal residential streets that are narrow and permanently lined with parked cars, most of these streets will have average speeds in the low 20s.

The old Welsh government guidelines section 5.10 which stated that
"20mph speed limits should only be used for individual roads or for a small network of roads. Research indicates that 20mph speed limits should only be used where mean vehicle speeds are 24mph or below or where traffic calming measures are planned as part of the speed management strategy". 
and that "Speed limits should be evidence led, self-explaining, and seek to reinforce people’s assessment of what is a safe speed to travel. Speed limits should encourage self-compliance and not be seen by drivers as being a target speed at which to drive in all circumstances."

It's intuitive to assume that whatever speed limit is set, it will become a target speed.
There was a time when I also made that assumption. However, I've seen a lot of data that shows just how much disparity there can be between speed limits and actual traffic speeds.

I've seen consistent data that show that average traffic speeds can be either massively over or under the speed limit depending on how the limit was set which shows that assumption to be false.
The lowest average speed I've seen for an urban 40-limit road is lower than the highest I've seen on an urban 20-limit road.
I've seen urban roads with non-compliance rates above 90% and three as high as 97% and many below 10% and as low as 1.1%, that's the level of disparity there is, is there something I'm supposed to be missing in that data?

My concern about many speed limit drops is that don't exist to improve safety either they exist to mislead people into thinking the road is much safer now the council stuck some signs up, or they exist to shift responsibility.
When most people are exceeding the speed limit every accident is the fault of the driver and the council is no longer accountable for poor road design or maintenance.

While I am stating that speed limits should not be seen as traffic calming per se, they're a legal tool.
For what difference, if any, they can make to actual speeds they're most effective when they match the road they're on, make sense and are perceived as reasonable.
Much as my cognitive bias is more towards trusting people and putting the emphasis more on the expectation of better driving behaviour, I can't let facts get in the way of that.
It is possible that 20mph or 25mph speed limits on roads such as ordinary residential streets and High streets may improve safety.
However, most drivers also don't go much faster than that on those streets anyway.
That's why UK limits rely on street lights rather than signs to vary the speed limits constantly as you go from side streets to main roads.
Side streets only ever had 30 limits in the same way narrow back roads have a 60 limit, the limit isn't meant to represent a sensible speed for all conditions or even all roads, far from it.

What I've never seen, is a study that recommends that speed limits should be set far below engineering recommendations and take no account of free-flowing traffic speeds.

Cardiff, unlike most cities with 20mph schemes, has not gone about creating a network of higher standard and main roads that are exempt, they have just gone and made the whole network 20 with little to no regard for differing road standards, even including some roads that seemed under-posted as a 30 limit.
With very few exceptions, the only 30 limits left are roads that used to have 40 limits. They've all gone now, as if they were all some kind of mistake and it only took 50 years to realise.
In Manchester, it was the higher standard roads they included that were the roads that saw speeds increase.
To show the level of disregard I'm seeing sections of the B4245 in and around Caldicot had levels of non-compliance close to 97% with the existing 30mph speed limit and an average speed of 40mph and still they lowered the speed limit to 20mph with zero changes to the road's design.
I've known of 20mph advocates who have spoken out against this practise of including some higher standard roads.

Side note, a road having speeds increase after a limit is lowered or decrease after a limit is raised is not the norm, but it's not as uncommon as you might think.

Portsmouth, which famously was the first city to introduce a city-wide 20 limits, seems to exempt pretty much all higher standard roads. Bristol has a network of roads exempt, but a committee seems to have come along and thrown a big dollop of non-uniformity onto that.
By including wide main roads, it can give pedestrians a false indication of actual traffic speed, Sat-Navs won't assume they are quicker and may direct more traffic through side streets.
There is also money being spent on signs which could otherwise be spent on engineering changes on some roads that can either give people more safe places to cross, or design roads that naturally reduced speeds.

None of those are the worst problem, the worst problem is the effect it has on people's perception of speed laws, it helps to make speeding normal and socially acceptable. On one of the highest standard roads in Bristol, the non-compliance rate was measured at 97.5!

When you have a speed limit like this on roads like the one pictured, you've gone well beyond a speed limit that is slightly below engineering recommendations and into the realm of having the limit set so far beyond what seems reasonable to most drivers, that many may only see the limit as irrelevant.
At that point, there's no point in having a posted limit.

Speed limits are important and this is how you bring them into contempt.
I was shocked that this road wasn't left out, This looks under-posted as a 30 limit.
It's wide, relatively straight, has refuges, excellent forward visibility, no frontages, no traffic calming, no parked cars, etc.
The limit suggested by the road's design is more like 40.
Remember, according to the guidelines, drivers shouldn't even see this as a target speed.

Why does that matter though, now anyone exceeding that speed is breaking the law, so what? It's done get used to it, right?
It could be understandable that he's assuming that he and everyone else just needs time to get used to the lower limit, however that shows a lack of understanding as to how speed limits work, what makes them effective and how we got the 30mph speed limit in the first place.
There was a time I also assumed that speed limits were something that you can just set and everybody goes that speed. However, it's much more nuanced than that.

In the past councils would not have been able to indiscriminately set speed limits low, the limits had to meet guidelines. Currently, the guideline is to use the mean average to set speed limits rather than 85th percentile speeds.
However, as 5mph increments are not allowed, that means for a sign only 20 limit the average speed only has to be 24mph. That means the speed limit can be set as much as 20% lower than the mean speed of traffic. That to me is already risible and even these guidelines are being ignored.
That wouldn't be so bad if there could be consequences, but councillors lack skin in the game.
If they raise or lower a speed limit with complete disregard for the guidelines or engineering recommendations and that causes accidents or even deaths to increase, there are no consequences nor could there be any legal consequences for it.
If it's popular with locals who just want a lower speed limit and automatically assume it will make them safer, they can just do it with impunity.

 

Speed limits VS speeds.

Unfortunately, when it comes to the debate about speed limits, all too often I will see people on both sides of it who don't understand what it's about. People talk about it like dropping the speed limit by 10mph means a drop in speed of 10mph.
In reality, it's much closer to 1mph, often with a colossal increase in non-compliance. Some roads will even see speeds increase. Any speed drop you do achieve is unlikely because those who are most likely to do harm are slowing down.

I understand the intuition behind the popularity of just setting the speed limit lower, lower speed equals safer roads, right? The fact that that contention is highly intuitive is the biggest problem with it.
I'm not talking about speeds; I'm talking about speed limits.
Fully understanding the difference between actual traffic speed and speed limits is the real trick.

Most speed limits, unlike people, can't adjust for the prevailing conditions, that's why they're meant to be set to assume ideal or at least favourable conditions.
When speed limits are set like that, it is possible to be going much too fast for the conditions while not speeding. That's why we have other laws such as reckless, careless and dangerous driving.

There used to be much more emphasis on driving to the prevailing conditions, not by numbers.

Traffic speeds are overwhelmingly dictated by the design of the road and the conditions at the time.
That's not an opinion it's just demonstrably the case, you don't have to like it.
People won't just drive as fast as they like. Contrary to very popular belief if you significantly raise a speed limit it's unlikely to result in a significant increase in actual traffic speeds unless you also change the road's design and vice versa.

This idea of just setting the speed limit really low is not new, that's how speed limits initially were meant to work and it was abandoned because didn't.

Prior to 1930, there was a blanket 20mph on all roads, this was increasingly being disobeyed to the extent that one Lord stated that "The existing speed limit was so universally disobeyed that its maintenance brought the law into contempt".
All limits were then abolished and replaced with the offence of reckless driving.
However, after 4 years it was decided that some sort of upper maximum was needed, and the 30mph limit was introduced for urban areas. 

People didn't get used to it, it was simply the closest round number to the speed most people would drive at, very close to or under with the absence of a speed limit, that's why it works. There may be some truth to people getting used to driving at 30mph as opposed to say 28 or 32mph for example.

If the speed limit is just set very low people won't simply get used to it, it will always be unnaturally slow.
As wrong, as it is, is as wrong as it will ever be. I understand that many people may not initially agree with the notion that you base speed limits on the speed people drive at, that's why it's important to understand why you base limits on speeds.
Setting speed limits too high or too low can reduce safety. Either way, you create a gulf between the speed limit posted and the one implied by the road's design.

Getting more people to drive at a more sensible speed is not a new idea, this sign by a school in Somerset is listed.

Many people in favour of very low limits may agree, even if they don't openly admit it, that people going speeds right down into the low 20s (providing the conditions at the time allow for it) are not genuinely at the level that should qualify as criminal behaviour, it's just that they see doing that as means to an end.
You may have read the statistic that 86% of car drivers on a road with a 20mph speed limit and 52% of drivers on a road with a 30mph speed limit exceed those speeds, however in 20 limits far fewer exceed 30mph.
First off, you shouldn't be setting speed limits low in the hope that many people will only dare drive X amount over it and this data is misleading as 20 limits have up to now mainly been put on roads that meet the guidelines for a 20 limit, so narrower residential streets.

I think it's likely that most people do not genuinely believe that motorists going speeds well under the current 30mph speed limit and all the way down into the low 20s, when conditions at the time are favourable, are serious a problem on the road.
Many would likely admit they're amongst the safer drivers.
It's more often the belief that "People drive unsafe speeds only go 5 or 10mph  over the speed limit" the only problem is, that's demonstrably not true, I wrote about this in a previous blog.

There are plenty of people out there who will drive at a speed that is unsafe for the prevailing conditions.
We all see people driving like idiots all the time.
If you ask a group of people why they want the speed limit lowered, they will often instantly allude to this sort of behaviour, and not people going speeds well below the mean traffic flow.
That behaviour is already illegal, either it's already over the speed limit or it's reckless driving.
However, since time immemorial people have been demanding that the speed limit gets lowered to deal with that problem, it's just naturally assumed to be a solution.

What are you actually prohibiting, when you just set a lower or very low speed limit, is the normal behaviour of ordinary motorists, people going speeds a way down into the low 20s on wide open roads even when there's good forward visibility and a lack of parked cars etc.
If just setting the speed limit really low was thought to be the solution to morons on the road, that would also have been the way you set them.
I've even heard of 20mph speed limits described as an "innovation" as if getting people to drive a sensible speed is a new idea no one had previously thought of, all you had to do was just set the speed limit really low to achieve this.

I once had a girlfriend test me for what sort of speeds I drove around normal residential streets of Shirehampton in Bristol, I'm talking side streets here, not urban main roads.
My speed tended towards 23mph, going as high as 25 and as low as 18mph. It varied according to what sort of line of sight I had in front of me  etc.
I told a 20mph campaigner about this and his first question was "what was the speed limit?".
Why ask that the question rather than asking me why my speed varied, or what was the weather  like, was it raining, was it foggy, how far ahead could I see or was there a one-legged juggler by the side of the road? I'm not interested in my speedo when driving around roads like that, nor should I be.

In 2017, I had two children run out on me on City Road in Cardiff,  I didn't hit them because I was travelling at a speed well below 30mph, the reason I was doing that was because I was on a busy street loaded with parked cars and pedestrians, I likely was going  a speed somewhere down in the low 20s and I was able to stop with plenty of room, had I been going 30mph, I would unlikely have killed them, but I may have hit them. I didn't think to myself "I'd better drive a speed in the low 20s" I just did it.

The answer to this anecdote is normally "you might be a sensible driver, but other people aren't".
Yes, exactly! So, they're not the sort of drivers to slow down because the limit is set very low.
Not just that, they're the least likely to, especially if the limit's set even lower speed than a more sensible person would naturally drive at.

The main point I'm making in this blog post is that the vast, overwhelming majority of people who drive dangerously or too fast for the prevailing conditions are not doing so simply because the speed limit lets them or it's only slightly over the posted speed limit.
That's not my opinion either, it's something that's measurable.
People still make the assumption that dropping the speed limit is the way to deal with these drivers.
It doesn't prohibit them more, in many ways it does the opposite and prohibits the behaviour of some of the most sensible drivers.

Another common reason given for these schemes is that it is to “encourage walking and cycling” and that’s a noble cause. However, the speed limit should not be used to encourage anything, it’s meant to prohibit people who drive like maniacs.
In most towns and cities sign only 20 limits only drop speeds by fewer than 2mph, in Bath for example they dropped by just 0.9mph and Manchester 0.7mph.
Even if  a council's more optimistic expectation for a drop is met it will only be 2mph, so they're expecting average speeds to be over the speed limit. That to me is vacuous.

That's for a 10mph drop in the speed pedestrians and other vulnerable road users are being told to expect the majority of traffic to be going a maxim of, this can cause people to become more complacent.
There may be a small drop in average speed and even 85th percentile speeds.
However, it's the fastest 1-5% of drivers who are some of the; least likely to slow down, the most likely to do harm and they're the drivers properly set speed limits are more efficient at targeting especially in the long term.
This is why, as counter-intuitive as might sound initially, artificially low speed limits can help to make roads more dangerous.

Just look at what the Twitter bio for 20's Plenty for Cornwall states.

They say they want to reduce speed from 30 to 20mph, not speed limits. They either don't know better, or worse, they do but decided to be misleading anyway.

The law is the law.

Why do we need to look at traffic speeds as a basis for setting speed limits, why can't we just set a speed limit, after all, people speeders are criminals, and speeding is bad...
Well yes, it would be if all speed limits were set correctly.

You may find that most people breaking the speed limit on roads where the limit does not match the road standard don't also go robbing old ladies.
You're more likely to find the same people are stopping for red lights, going slowly along narrow residential streets, passing cyclists with plenty of space, slowing down for hazards, waving people across the road or going around offering people free hugs.
It turns out most people generally tend to be agreeable, rational and reasonable and have an aversion to having crashes or running people over.
So, when you find that a road has over 90% non-compliance, what's going on there?
If you look at roads that have seemingly generous speed limits, compliance is normally much higher, but speeds aren't. Either that's just a big coincidence, or there's more going on there.

Not only are you, by artificially dropping the speed limit too low,  making going the speed limit counter-intuitive, but this also makes exceeding it normal and socially acceptable.
Those attempting to do nothing more than obey the speed limit increase their accident risk by driving significantly slower than the mean traffic flow, something that would normally be against the highway code.

For some people, it doesn't seem to matter if there is over 90% non-compliance.
Any argument I can make as to why non-compliance high is not demonstrable of a speed limits being set too low, no matter how well it's articulated it can be dismissed simply because anyone not complying is doing something illegal therefore they're in the wrong.
If there's 90% non-compliance, then 90% of drivers are wrong, therefore they're the only ones to blame.
The crux of this argument is a logical fallacy called appeal to the law and the law is the law.
If very high non-compliance with a law can't be seen as indicative that the law itself is incorrect, then you could, make up any law about anything and say the same thing.
You could set the limit to 2mph or set a law that says you must sit on a chair and eat milk, bread and pine needles for sustenance, that doesn't make it a good law.
If the non-compliance rate is over 90% that should tell you that either the limit is wrong or the design of the road is, chest-beating and shouting "it's the law, shut up and obey" louder and louder isn't going to work. Someone's kicking the can down the road, that's not an adequate counter-argument to someone trying to articulately explain what exacerbates non-compliance with said law, it's just dismissive.
If people are told to do something, but can’t see the reason for it, the reason seems defective or inappropriate for the context of the moment, people are likely to be disobedient.

However, if you don't accept that. I'd also point out that most speeding, if the limit is set too low, is mostly not down to wilful non-compliance, it's more down to how our brains function, people will just automatically default to driving at a speed that feels natural.
I think that contention may need a more detailed explanation which can be found here given by road safety campaigner and traffic engineer from the charity Strong Towns Charles Marohn.
In short, if a road design lends itself to a particular speed, most people will just drive that speed, mostly without even thinking about it.
People may also state that obeying the speed limit is easy, only in the same way driving under 5mph to park is easy or walking sideways like a crab is easy, something being in a literal sense easy initially doesn't make it intuitive to sustain over a long period, this is an example of equivocation.
Similar sentiments came from George Ferguson the Bristol mayor behind its 20mph scheme who was then caught speeding.
He was going 35mph on a road designed for a 40 limit that now has a posted 30 limit.

I'd contend that the speed limit is a legal tool, there to single out the behaviour of the small number of drivers who will drive with a disregard for their own and others' safety, if you've got over 90% non-compliance, this method of singling people out becomes difficult to say the least.

That's why it's important to take into account traffic speeds when you set limits.
You look at real-world behaviour to set real-world prohibitions. As Charles Marohn states the "observation of human behaviour has long been a source of frustration for safety advocates".

I write this not because I want to drive faster, it's because I think speed limits are an important tool for road safety. However, it's easy to just dismiss anyone complaining about this with appeals to motive, appeals to the stone or appeals to the law. 
I don't think the contention that "The normally careful and competent actions of a reasonable person should be considered legal." is controversial.
There is such a thing as concurring opinion. Not everyone against it is a boy racer or white van driver, they're the ones who properly set speed limits are better at targeting.

So, how do we make roads safer?

On faster main roads it's important to give people safe places to cross so investment in crossing or pedestrian refuge island are important.

If you really want to slow people down in areas where high numbers of vehicles and people interact then you need to redesign the roads so you have streets designed for people and that works to create uncertainty in drivers' minds, things such as continuous footpaths and removing traffic controls cause people to naturally drive slower and they're not aggrieved by it. 

 

 In this picture, you have a main road designed for vehicles and side streets designed for people and vehicles to interact and a junction designed to force motorists to slow down.

 

If you set a law that shows people contempt, people are unlikely to reciprocate by respecting it, this is down to the Pygmalion effect, showing people more respect tends to lead to them being more willing to obey rules they perceive as reasonable. This is likely why in some cases raising a speed limit has been known to reduce average speeds.
If the law comes across as unreasonable or arbitrary, people not just then have contempt for that law, but also the people who set that law, the people who enforce that law and even the people who obey that law. Yet these limits are being set by people who claim to want exactly the opposite of that.
The people who are in favour of dropping the speed limits are often the most vocal that speed limits must be obeyed, respected and enforced and yet they're responsible for doing the thing that leads to extremely high non-compliance rates and people thinking the speed limit is a joke. 

Drivers shouldn't see the speed limit as a joke, they should be taking them seriously.