Road Safety News

Report calls for ‘evidence-based’ speed interventions

Monday 20th November 2017

A new report, published to coincide with the start of Road Safety Week 2017, sets out to ‘debunk some popular myths’ and calls for ‘evidence-based’ interventions focusing on speed.

The report, Save Lives, Slow Down, is based on contributions from a number of winners of Prince Michael International Road Safety Awards including Highways England, PACTS, RAC Foundation, Road Safety Analysis, Safer Roads Berkshire and TfL.

The report urges ‘restraint’ with regard to the implementation of 20mph schemes, adding that popular interventions ‘may not always work well’, and that ‘initially-unpopular schemes can deliver powerful results’.

‘Key facts’ highlighted in the report include:

  • A 5% reduction in average speed can result in a 30% reduction in fatal traffic crashes
  • 59% of all fatalities in Great Britain occur on country roads where limits are typically 60mph
  • The risk of a pedestrian being killed if hit by the front of a car is estimated to be 1% at an impact speed of 20 mph, 7% at 30 mph and 31% at 40 mph
  • Inappropriate or excessive speed are two of the contributory factors most often recorded by police crash data; but ‘in-depth studies’ say that the true level may be three times higher

20mph limits

Talking about 20mph limits, Richard Owen, director of Road Safety Analysis, urges restraint in the ‘rush to introduce blanket 20mph limits in all towns and cities’.

He says that 20mph zones often already have lower average speed and achieve compliance and safety improvements through engineering and signing measures. Conversely, signed-only 20mph limits often see poor compliance.

Richard Owen added that, ‘early evidence from the latest and most comprehensive study suggests signed-only-limits result in just a 0.7mph reduction in average speeds.

‘Acceptable, affordable and effective’ interventions

Adrian Walsh, director of RoadSafe, said: “If a 5% reduction in average speed can result in a 30% reduction in fatal traffic crashes, it is hard to think of any other low-cost intervention that could deliver such a potentially huge reduction in human suffering and economic loss globally.

“However, the challenge for politicians and road safety professionals is to find interventions that are acceptable, affordable and effective. Popular may not always work well; and initially-unpopular schemes can deliver powerful results.”

‘Highly effective’ average speed cameras

The report recognises resistance to the widespread use of speed humps and cameras in residential streets but acknowledges the effectiveness of average speed cameras strategically placed on some higher-speed roads.

Adrian Walsh added: “Managing speed can never be a one-size-fits-all process.

“Cutting the number of fatal and serious, speed-related road crashes must make use of the wide range of effective, evidence-based speed management solutions available.

“These include…setting appropriate speeds limits suitable for the function of the road, and enforcement to encourage road users to comply with speed limits.”

The report includes a case study of the ‘highly effective’ average speed camera scheme on the A9 in Scotland which, it is claimed, has resulted in a 50% reduction in all casualties and a 33% cut in fatalities.

Adrian Walsh concluded: “With the 2020 Global target to reduce road fatalities by 50% fast approaching, local, regional and national governments are encouraged to implement effective speed management policies as a matter of urgency to further reduce casualties.

“If we want to make a tangible, measurable difference, we must take tough actions that focus on delivering life-saving results.”

Category: Speed.



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The evidence from trauma centres is such that those incidents where the speed is such that participants can avoid a collision never make it to the trauma centre. And whilst the "mechanism" of conflict between soft tissue and hard objects is certainly a factor in injury, not bringing those two into contact is the biggest factor in avoiding injury.

I am not sure what physics you are relying on Duncan. You say :-

"yet the human retina can resolve something moving at 2mph a foot away which equates to the same rate of positional change as something moving at 100mph just a few yards away."

There is a complete difference between "resolving" something moving and having the processing power to work out what speed it is looming. Although they are only "old" units I am sure that last time I looked there were 6 feet in 2 yards. Hence the speed of an object moving 2 yards away to have the same angular movement as one one away foot at 2mph would be surely be 12mph (ie 6 x 2). If that's the "hard evidence" you are using then its rather flawed.

Opinion is supported by evidence and when WHO, SWOV, ETSC, say so then I tend to take this as credible. Other orgs saying that 30km/h is the right speed limit for pedestrians and cyclists mixing with cars include iRAP and the Global Network for Road Safety Legislators. In particular :-
"There is strong evidence that wherever motorised traffic mixes with vulnerable road users, such as pedestrians, cyclists and mopeds, the speed limit should be set at or under 30 km/h."
Rod King, Warrington, 20's Plenty for Us

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Talking of roundabouts, here is an interesting news item seen today
Rod King, Warrington - 20's Plenty for Us

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I thought that was the point I was making Nick! i.e. carelessness and recklessness being at the heart of collisions - however, the illegal actions of road users - particularly the motorised ones - will make it more likely. Spend an hour or so at a mini-roundabout and count the near collisions when the directions are not followed. I recently did 360 degree turn around a mini-roundabout to come back on myself, only to meet side-on, a vehicle who had ignored the directions and tried to go around anti-clockwise...wouldn't have happened if he'd done it properly. Illegal actions on the road don't always result in collisions I agree, but they make it far more likely.
Hugh Jones, Cheshire

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Hugh - it is possible to "break the law" without injuring anyone. Conversely, it is possible to circumnavigate a mini-roundabout in a legal fashion and cause a collision. It is the recklessness, careless behaviours (among other factors) which increase the potential for a collision to occur. Granted I have oversimplified but I think the point still stands.
Nick, Lancashire

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Bit surprised at your question Nick (although directed at Paul) - how could wrong behaviour at mini-roundabouts not cause collisions? Anywhere there's conflict on the highway, with carelessness and recklessness at the root of it, there will be collisions.
Hugh Jones, Cheshire

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Paul, is there any evidence that drivers cutting across mini-roundabouts are causing casualties/collisions? It may be annoying but is it a "problem"?
Nick, Lancashire

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What is it you seek evidence of Duncan, that may be fairly obvious to others? I'm genuinely not sure. Is it the role of speed (which Rod has explained anyway)? Collision prevention generally or... what? These subjects must have been covered countless times on the forum.
Hugh Jones, Cheshire

Agree (3) | Disagree (2)

Physics and engineering do provide clues that's for sure Rod, but they are only clues and cannot be counted as hard evidence. The evidence from the trauma centres for example tells us that "it's mechanism rather than speed that determines the injury outcome" and indeed there is a wealth of empirical data to support that observation. Yes this may also be a clue, but if you want to include clues then you must include them all.

We did evolve in a world with very few ground based bodies moving above 20mph, yet the human retina can resolve something moving at 2mph a foot away which equates to the same rate of positional change as something moving at 100mph just a few yards away. This is the type of hard evidence which should be informing our debate rather than the simplistic opinions which seem to dominate it at the moment.

As to an 'opinion' that 30kmh is the maximum safe speed where pedestrians and cyclists mix with motorised vehicles, it is still just an opinion because it too is not supported by any evidence other than guesswork and crude extrapolation.

I would ask that people don't bring us opinions, opinion polls or cherry picked clues just evidence and then, but only then might we start to believe in the potential effectiveness of various campaigns.
Duncan MacKillop. No surprise - No accident.

Agree (4) | Disagree (5)

Rod, you do not need to remind us that crashes will stop happening if all traffic travels at 0 mph or even that slower traffic is more desirable in some places at some times or even that if traffic speeds never exceeded 20mph there would be fewer road casualties - we all agree with all that, it is common sense, it is the laws of physics and it is incontrovertible, so you do not need to keep repeating it.

However, the notion that poles with 20 mph speed limit signs on them can or do, in any way, shape or form, deliver those speeds or even significantly influence traffic speeds at all is generally disputed. So please stop conflating traffic speeds with with posted limits. That we may need sub-20mph speeds does not imply that we need 20mph speed limits.

We all know urban roads with 30mph limits where traffic speed never exceeds walking pace and we all know urban roads with 20mph limits where the traffic speeds are closer to 30mph. Accept the reality - speed limits are not reflected in road speeds (although the opposite may often be the case). It is time to stop flogging this very dead horse, to stop trying to persuade (even mislead) people that speed limits are the answer, or even part of the answer, to inappropriate speeds. It is time to accept the reality that whatever it is that does influence traffic speeds, it certainly does not come in the form of a number on a road sign.
Charles, England

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Paul Teddington (or is it Paul from Teddington) is right about mini-roundabouts - routinely they are probably the most contravened driving law, with typically one in every two motorists not going around clockwise, going instead, either straight across the raised centre or even worse, going anti-clockwise to cut the corner of a right turn from the roundabout. Ironically, it's more prolific than speeding.
Hugh Jones, Cheshire

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The report is welcomed.

Speed management, speed enforcement, and by proxy road safety / safer roads / safe systems / vision zero and what ever else you'd care to call it are all 9/10ths Politics and politics.

Time for leadership from Politicians.
Nadeem Up North

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The report gives roundabouts as a means of traffic calming and shows a mini-roundabout with a grassy island. In reality mini-roundabouts have painted roundels which are simply ignored. Research on some means of deterring driving over whilst still allowing buses would be welcome.
Paul Teddington

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Interesting comments. A few quick responses:
* RoadSafe led on this. PACTS was pleased to be involved and support it.
* Sorry that the electronic report is hard to read. I will pass on this information. There are (or were) had copies available. Try RoadSafe.
* PACTS agrees that STATS19 has many limitations, particularity on contributory factors, and we are pushing hard for more comprehensive in-depth collision investigation.
* ISA is in the proposed changes to the EU vehicle safety regs (GSR/PSR). Please encourage DfT to get behind them.
David Davies, London

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Physics and engineering provide quite a few clues as to why lower speeds provide so many benefits. The knowledge that for millennia homo sapiens has evolved in a world with very few ground based bodies moving above 20mph is another factor. Add in opinion that 30kmh is the maximum safe speed where pedestrians and cyclists mix with motorised vehicles. Then throw in the visual acuity development of children regarding faster moving objects. It also happens to reduce speeds. Put all this against the minimal benefits of travelling faster than 20mph between congestion and stopping points and you realise that there is very little to be gained from allowing speeds higher than 20mph unless there is specific provision to allow pedestrians and cyclists protected mobility.

And with the support of 70% of those surveyed it would appear to be a "will of the people" that is far more beneficial and popular than one recent proposal in the UK.
Rod King, Warrington - 20's Plenty for Us

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A great pity that the report is practically unreadable in its electronic form and completely unreadable when printed off.

As far as I can tell, however, it doesn't benefit from the input of criminologists, who would caution against the speed camera-type approach to top speed control. This is a serious omission at a time when it is possible gain the level of control necessary without criminalising drivers.

I refer, of course, to Intelligent Speed Assistance - a mature technology of which government seems unaware ...
Andrew Fraser STIRLING

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Observations of behaviour on the roads could be Rod's answer Duncan, as it would be mine. Data not really necessary for what our common sense can tell us in the first place.
Hugh Jones, Cheshire

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If the sparse information on speed in Stats 19 tells us very little about how speed or a limit influences any casualties Rod, on what data are you basing your campaign?
Duncan MacKillop. No surprise - No accident.

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In his first two paragraphs, Rod has neatly outlined the relevance of speed to collisions and few would argue with the physics, but the problem I've found is that many speeders have not grasped this elementary, but fundamental relationship, between their speed and the ability to avoid impact. Slogans like "speed kills" or "slow down - save lives" and the need for speed management is lost on these people and the concept of how their speed relates to their and other road users' safety, therefore needs to be at the heart of any interventions. There are many clips on You Tube which show how real collisions could have been avoided through slower speeds and the understanding of that by the drivers. If that still doesn't get through to them, then further education would seem pointless and for those still in denial, hit them with discreet enforcement... as was said by a panelist at the recent road safety conference "We're too kind to speeders".
Hugh Jones, Cheshire

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No-one that I know of doubts that incidents can be created by distractions and errors of judgement. But what takes those incidents beyond the control of the participants and creates collisions is the ability of participants to cope with the rate at which decisions and actions have to be made in order to avoid the collision.

Here speed is an intrinsic component not only of the time and space available for those decisions and actions to be made, but also the response of the vehicle systems in terms of controls, brakes and handling.

Speed is critical to incidents being turned into collisions regardless of the legal limit that applies. It also increases the severity of any crash consequences including casualties.

Of course, what may be a speed that is "compliant" in one case may only be so because the limit is not set taking due consideration of all the hazards but relies on some unconsidered national limit set in 1934.

A 28mph speed that may be compliant with the default 1934 limit of 30mph would be non-compliant in an authority that had decided to follow DfT guidance and set 20mph as the limit for such a street.

The sparse information on speed in Stats 19 tells us very little about how speed or a limit influences any casualties because it fails to detail the influence of speed in the progress of an incident through to a crash and subsequent casualty.
Rod King, Warrington - 20's Plenty for Us

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My comment would be "How do they know?"

Once again it shows the futility and shortcomings of Stats 19, which I presume is the source of this statistic.

There's no doubt a mix of the reckless and the careless on our roads, but in the context of speeding, whatever the mindset of the perpetrators their actions still need addressing.
Hugh Jones, Cheshire

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Is these any evidence available to suggest that simple errors of perception or judgement by otherwise compliant persons can often be the result of driver distraction or inattention? I would suggest that this statement is no more than the common manifestation of a cognitive bias such as the fundamental attribution error leading to an unsupported conclusion.

The road safety industry tells us that it is 'evidence based' yet far too often we see conclusions reached without any evidence to support those conclusions. Dr Shaun Helman from the TRL stated during the recent conference that there is very little evidence available to support any conclusions and with the ease with which attribution errors are made it's not all that surprising.
Duncan MacKillop. No surprise - No accident.

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Certainly Duncan

However, it does depend on what the authors mean exactly by 'compliant persons'...
But "Simple errors of perception or judgement by otherwise compliant persons" can often be the result of driver distraction or inattention. I'm pretty sure those root causes would not show up in the majority of Stats 19 reports. I don't think many drivers are likely to own up those causes when a fine or insurance claim may be influenced if they did.
Pat, Wales

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Couldn't help but notice the following box-out in the report.

"30% of serious crashes are caused by deliberate violations and risk-taking behaviour. The majority result from simple errors of perception or judgement by otherwise compliant persons."

Maybe one of the road safety professionals on this forum might like to comment on this?
Duncan MacKillop. No surprise - No accident.

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I note that the article above says "The report urges ‘restraint’ with regard to the implementation of 20mph schemes, adding that popular interventions ‘may not always work well’, and that ‘initially-unpopular schemes can deliver powerful results’." (and I accept that this may be the impression given by the Press Release)

Actually, the report does not say this. The words "urge" and "restraint" are not in the report at all and the "popular is not necessarily effective" comment is not in a paragraph on 20mph limits.

Whether Richard Owen ever said that is debatable, but it certainly was not deemed relevant enough to be documented in the report

But the report does quote that "A 1mph reduction typically results in a 6% decrease in casualties" and that "To ensure a 'Safe System' in which serious injury to children is prevented, urban traffic speeds on residential streets and on school routes where traffic and children come into conflict must be kept below 30km/h."

Given the overwhelming opinion and evidence that 30km/h is the right maximum speed shouldn't we be focusing far more on ways to deliver higher compliance through engagement, education, enforcement, and even some engineering.

Our enforcement methods are antiquarian using old technology and based on casualty cluster locations rather than maximising generic compliance.

Its time we ended the pandering to the enforcement sensibilities of those road users who wrap themselves in a ton of steel with high viz sparse camera enforcement and started to use endemic and covert technology. Or to put it into a soundbites our government understands "a speed limit is a speed limit".
Rod King, Warrington - 20's Plenty for Us

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Bob: Further comment - you asked 'what's the problem' when the vast majority are not driving at inappropriate speeds? Well, it's those who are driving at inappropriate speeds that is the problem, I would have thought. I'm only adding this comment because Paul's video clip highlights it: the small red car ahead of the lorry drove past the stationary school bus at a slower, more appropriate speed i.e. ready to slow/stop, whereas the following lorry with the much longer stopping distance didn't, and only through luck was there no impact. As for irresponsible people running out from behind a stationary bus - well it was a child - responsible drivers should anticipate that possibility.
Hugh Jones, Cheshire

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Very disappointed. I already spend too much time in front of a computer screen so I wonder if the authors have a plain text version of this for those of us who prefer to read such reports on paper? Much of the downloaded report is unreadable in printed form as I found out yesterday evening. White text on coloured background just does not work well in print.
Pat, Wales

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We need a total rethink on road safety - looking at all aspects. Think speed and car/truck are responsible for all accidents? Well sometimes it is just irresponsible people as you will see in this video - people running out from behind a stationary bus -

Agree (11) | Disagree (5)

Whilst your well-known concern about too-close following is acknowledged and hopefully supported Bob, with respect, your lack of perception of motorists' too high a speed seems to be alarmingly lacking. The generalisation in your second para is way off the mark and quite removed from the reality of everyday life on the roads. Too high speeds and those who do it are still the biggest problem on the roads - closely followed by too-close following (pun intended).
Hugh Jones, Cheshire

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I am only going to make one comment and that is as follows.

When next out and about take a look at every motorway or every rural road or urban street scene and one can see that vehicles are travelling in the same direction and generally all at or about the same speed. The vast majority are not exceeding or breaking the law on speed and many more are not being driven at inappropriate speeds either so what's the problem? What causes the collisions or incidents? Is it merely speed? Seems not.

What is in fact the main cause of so many collisions or accidents? One which is obviously not speed and that is a total and complete lack of knowledge of the dangers of not keeping sufficent safe following on or sight distances between vehicles. Everything a motorists and even an advanced motorist should know about and be doing but perhaps isn't.

It is that danger that can be seen every time one looks at a road scene and objectively views just how close together some traffic travels. So closely together and in line that they are like like sheep. Further, insufficient space in which to stop in is a common fault and a common lack of knowledge of braking distances and of stopping or slowing distances overall.
Bob Craven Lancs

Agree (14) | Disagree (2)

On the subject of a vehicle's speed just before a collision which has traditionally been difficult, if not impossible to establish with certainty, I recently learnt that if a collision causes an air-bag to be deployed, the control module can be interrogated and data retrieved which gives speeds up to the trigger moment, as well as brake action and other data relevant to crash investigation. Does anyone know if this is routinely done in the UK, as it has been for a while in other parts of the world?
Hugh Jones, Cheshire

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