By Nick Bell
Over the years I have met several training delegates and auditees who told me a similar story: “Our safety department won’t let us reduce the severity rating on risk assessments”.
These people worked in a host of different industries: Construction, rail, manufacturing and the public sector. They were using risk assessment methodologies that required them to score severity and likelihood.
It happened again recently and I decided it is time to call out the industry on this issue.
I urge readers to think about their own stance: Is it sometimes possible to reduce severity of harm as well as or instead of reducing the likelihood of harm occurring?
Anyone with a reasonable grasp of the principles of prevention, a cornerstone of how we manage risk, will hopefully say “yes” and have a number of examples. I offer just a few of my own.
I once undertook a health and safety survey at a galvanizer which had historically used a strong bleach solution to clean metal work prior to dipping it into molten zinc. In the past, staff had come into frequent contact with the solution and suffered damage to their skin. The galvanizer had redesigned the bath, changed the dipping process and altered the PPE regime to reduce the chance of people getting the solution onto their skin (i.e. reduced likelihood of harm occurring).
The managers trialled different concentrations of bleach solution and found that a much weaker (and much cheaper) concentration was equally effective at cleaning the metal work. In the event that the liquid came into contact with people’s skin it was far less harmful (i.e. severity was reduced). This was supported through improved welfare arrangements enabling operatives to promptly wash off any solution.
We can also tackle energy sources on a number of fronts. For example, I was inspecting a manufacturing site and noticed a very noisy motor (feeding air handling equipment) above a production area. It could not be moved outside (it would cause a nuisance) and it was uneconomic to replace it with an intrinsically quieter motor. A noise assessment was instructed and presented a range of options. The motor could be suitably maintained and have acoustic treatment to reduce the amplitude of noise it produces. .
Duration, frequency or amplitude of noise exposure could be reduced by effective organisation of the workplace (e.g. positioning the motor a suitable distance away from longer duration jobs, such as stacking, wrapping and packing or vice versa). The employer might then consider the use of PPE. Routine monitoring of the arrangements and audiometry testing would identify if controls are slipping. Collectively, these measures will serve to reduce exposure to the hazard, the likelihood of harm resulting from that exposure and the potential extent of that harm (i.e. severity): We would not reasonably foresee rapid and significant hearing loss. 
The whole premise of fall protection systems, such as nets, is that while they do not reduce the likelihood of someone falling, they reduce the consequences of a fall. Someone could obviously still be injured but far less severely than if they fell onto a concrete floor.
Behind this instruction may be a well-meaning sentiment that we should reduce the likelihood of a hazardous event occurring rather than protecting against the consequences. I concede there are situations where the foreseeable outcome will always be dire (e.g. a building catching fire).
However, a dogmatic stance that severity cannot be reduced is more than just a technical inaccuracy: It undermines effective and proportionate risk management. These are some of my concerns.
If you are at loggerheads over this issue, it may be useful to talk with workers and managers to get their views and collect examples. A few photographs, perhaps turned into mini-case studies, could become useful discussion starters and training aides. This will help us adopt the role of credible, solution-focussed enablers and coaches. Potentially, there’s a discussion to be had about how useful it is to numerically score risks but that’s one for another day.
Nick – your bleach example is spurious, as you have not reduced the severity of the original risk that was identified. By changing the substance from the original, more harmful bleach; you’ve simply replaced one for another. the severity of harm from the original, stronger bleach was not reduced. When working at significant height, where falling and hitting the ground could lead to death; stopping someone from falling firstly and hitting the ground secondly is what is required. Stopping them from doing so, does not reduce the severity if the risk controls failed. If a significant hazard is identified and… Read more »
The confusion stems from how the risk is stated. If the risk is stated as fall from height, then the net would reduce severity. However falling does not cause injury, the injury is caused because of a fall from height. Hence the risk should be correctly stated as “hitting the ground after a fall from height”. Hence a net would reduce the likelihood of hitting the ground. However one does want to prevent even the fall from height , hence the harness. So the implementation of sequential controls over time where the probability of the first control failing creates the… Read more »
I agree with Bob regarding the original risk still existing. In many of these examples, the original risk (with the higher hazard exposure level) still exists, and a new risk (with a lower hazard exposure level) has been introduced. Both should be analyzed and controlled appropriately. I agree with Sumita regarding other risks also existing. In many of these examples, the original risk exists, and a separate later risk also exists. Both should be analyzed and controlled appropriately. Underlying both of these comments is the identification of multiple hazardous situations where each of these should have independent analysis, assessment, and… Read more »
Hi John, I totally agree with you on the risk assessment issues, just one thing that most of safety professionals do wrong, especially when you create a Risk Assessment on a product or plant/equipment you manufacture and sell to a customer is to use the terminology “Residual” Risk” In legal terms when you submit that Risk Assessment to a customer means there is still risk remaining on the product you supplied. Rather use the word “Controlled” risk in the document, which means that your risk assessment team has put controls in to as low as reasonably practical. This we had… Read more »
using safety net u simply prevented the fall to the ground. the original risk was falling from height and hitting ground.
If you’re calculating residual risk from the likelihood of controls failing, then all risk assessments should result in extensive severity and frequent likelihood outcomes. For example, I would never allow an operator to use a harness and lanyard if I understood there was a potential for the anchor point, or the PPE to fail. That risk would be captured and mitigated against. Humans also wilfully breach control measures; shall we then say that likelihood can increase due to the unforseeable nature of humas and human factors?
Hi Bob. Thanks for the feedback. I think quantitative risk assessments could be Marmite for our profession! I certainly agree that we need to keep things practical and use the knowledge and experience of the people involved. The point I was making with the bleach is that I believe the company chose to (in the words of the principles of prevention) “replace the dangerous by the non-dangerous or the less dangerous”. COSHH also asks us to consider whether there is a safer form of the product that we can use. My concern is that, despite these principles, people are being… Read more »
I tend to follow the simple mantra, that severity can change, but likelihood is more probable overall when looking at most of the control options over a whole general risk assessment. As long as the 5 steps, suitable and sufficient and principles of prevention (including specific versions in other hazard regulations like COSHH) are adhered to and that the controls work, job done! The rest is academic indulgence… by which time your employees have started to pull out all their remaining teeth! I often find people conflate the meaning of likelihood and severity together.. Unless you have altered the intensity… Read more »
I agree with your comments, particularly the marmite I do feel a lot of people engaged in health and safety bring our profession into question when not engaging a proportion of common sense
Nick, very good article and a well presented argument and could not have out it better myself. An obvious example of a reduction in severity ratings can be seen with car design. The introduction of seat belts in the 1980’s saw an almost overnight reduction in the type of injuries sustained. As a front line medic I witnessed a drastic reduction in major chest and lower limb trauma. Similarly, the air bags now fitted have reduced severity of injury further. Vehicles collisions that previously had the potential for a fatal outcome we now find car occupants walking away from them.… Read more »
HSE themselves have stated in previous guidance, that it’s important not to “get too hung up on the numbers, it’s the process of doing the risk assessment that’s the important thing, not the outputs”. Everyone’s viewpoints differ slightly, so unless one person is doing all the risk assessments (and the person best placed to assess risk is the person doing the job) there will be variance anyway. I’m no fan of the 5×5 matrix (or any odd sum matrix where you have a middle option) because I prefer there to be an active choice to place the assessed risk “above… Read more »
Couldn’t agree more! I have had this same , sometimes heated, discussion with ‘Safety Proffesionals’ and some just don’t seem to get it. Bob, you state, “you’ve simply replaced one for another. the severity of harm from the original, stronger bleach was not reduced.” It was reduced, because it’s not there anymore! The risk asessment is to identify how to make the TASK safer, not the (in this case) substance. Nick has shown that. They looked at a task that HAD to be carried out , improved PPE , methods, first aid provisions etc. etc. But in the end, there… Read more »
100%agree. An even simpler example of reduced severity is the use of a shock absorbing lanyard. The message to managers doing risk assessments should be apply your hierarchy of controls. If you find that you are unable to reduce the likelihood before you get to PPE (which does happen), then choose PPE that will reduce the severity. A shock absorbing lanyard is intended to reduce the consequence of the fall, even if you have been unable to reduce the probability of the fall occurring. Nebosh concede this to be true in their course material.
Nick A good piece and a point always debated, I think the important part here is if we don’t change anything then the outcome remains the same, however if we go back and look at what we can do to change the process or what mitigation’s can be implemented to improve/reduce risk is good. At that point you can then look at the likelihood / severity that was set at the first pass and see what can be changed. What a lot of people tend to do is look at the task without looking at mitigation in place.The bleach example… Read more »
Nick, it is very interesting that in each scenario that you use, you actually reduce the potency of the chemical and the noise of the machine. Now, if you reduce sulphuric acid to vinegar, then yes the severity will of course reduce. If you reduce the noise (by whatever means) to ALARP then again, of course you will reduce the severity.
Here’s one to consider, a engineering firm has a guillotine machine, the staff are protected by state of the art mechanical guarding and robust managerial processes. Does the severity reduce?
Steve I would say of course not.
But I dont think that is what Nick is trying to say. He is making the point that severeity CAN reduce in certain circumstances and with appropriate controls. The old belief (and I’ve heard this uttered by CMIOSH members) is that severity CAN NEVER reduce.
That’s blantantly wrong and such an intransigent position only restricts and stymies the development of control measures.
Safety management is not something set in stone. It changes all the time, is fluid and adapts to different circumstances.
Mechanical guarding will reduce the likelihood of harm through contact with the guillotine. The severity of harm will remain the same if the guard is bypassed or fails. For example: An individual walks across a construction site and is struck on the head by a falling object (no head protection) resulting in serious injury. The person behind them is struck by a similar object (head protection worn) and suffers a less serious injury. We have reduced the severity of harm through the use of personal protective equipment (the last resort) We should have reduced the likelihood of objects falling in… Read more »
Severity remains the same. The control measures reduce the likelihood of persons being exposed to the hazard, but should these fail, they will still be exposed to the same hazard; in this case.
Are we saying that a hard hat will not reduce the severity of harm through exposure to the same hazard? The severity of harm will be lower if the item of PPE is worn correctly; in this case.
It reduces the likelihood of harm, but there is still the possibility that the hard hat fails to sufficiently cushion the impact. Just because it makes it more likely that a less severe outcome is the result of an incident, does not make it impossible that the most severe outcome occurs. It just makes the most severe outcome less likely. The severity would only be changed if the falling material is changed (e.g. if a block of concrete is replaced with a block of foam).
I fully agree with Nick that one can not only reduce the likelihood of an event but also its severity. This is a fundamental principle of safety management – it’s even taught on introductory courses such as the IOSH Managing Safety – so how on earth can a “safety department” argue that the severity cannot be reduced? It seriously calls into question the basic competency of the people running such “safety departments”. If they give the wrong advice on this key topic then what else are they getting wrong? How much damage are they causing to the profession of health… Read more »
If the controls fail, the severity is the same. By implementing controls you are looking at reducing the likelihood of the event occurring
I have to say that the arguments put forward by ‘Bob’ seem to be arguments for the sake of arguments. Even the most basic of risk assessment training courses teach that reduction in overall risk will be achieved in one of three ways: 1. Reduction in likelihood 2. Reduction in severity 3. Reduction in both If a dangerous substance is replaced is replaced by a less dangerous one then the severity has been reduced. while I agree that the severity of the original bleach has not been reduced it is not being used having been replaced by a substance with… Read more »
Health and Safety risk management is a practical subject reflecting the real world of work. We impose theories and their associated definitions in an effort to communicate our ideas about how to create and maintain a workplace that is safe and free from danger. We define risk as severity of outcome multiplied by frequency of exposure. The notion that you can’t alter the “severity” in a given risk scenario is a truism. In the examples given I would say that the risk scenario is changed in the first (chemical) and the frequency of exposure is changed in the remaining two… Read more »
Great points Nick. There is a huge gap in the understanding of risk assessments and they are too often treated as purely documents to be filed away. I have had the experience of what you describe where the safety department of a large infrastructure contract insisted that because I had reduced the risk of electrocution due to contact with 25kV cables, I had to also show a reduced severity in the risk matrix otherwise they would not sign off the risk assessment. Their logic was that before controls, touching the wire would cause death but after the controls to minimise… Read more »
Nick, A tad confused, perhaps? The whole point of asserting — absolutely correctly — that severity cannot be reduced is to oblige the assessor where appropriate to re-address the hazard. Only by eliminating, diminishing or substituting the hazard will severity be reduced. The replacement hazard may or may not have less severe consequences associated with it. But the fact remains that had the original hazard been allowed to persist, reduction in severity would not have been attainable. To be effective the assessment process must be iterative in this way and not lose focus on the hazard. That’s why we assert… Read more »
Nick, I wholeheartedly agree with you. I have had this stance for a number of years and have managed to change many view points over the years among my fellow professionals and new work colleagues at various locations and industries.
This subject for many H&S professionals seems to have been a case of “the emperor’s new clothes”, I’m really glad that you have aired this subject and look forward to seeing the feedback from those who standby the stance that you can’t reduce the severity.
Excellent article!
Regards
Paul
Hi Nick I agree with your observations. Working in engineering construction for many years, its surprising to find that even now I come across many HSE professionals who simply cannot accept that reduction in severity is achievable. When debating the issue I tend to use the ‘fall from height’ scenario. Let’s assume a worker is on a second storey roof. Of course it is always better to prevent the worker falling but let us say that there was no edge protection in place or fall prevention/arrest harness being worn by a worker. The worker trips and goes over the leading… Read more »
I agree partly with Nick’s views, but I am quite surprised to hear that there are some advisors who state that severity cant be reduced. I have always taken the stance that addressing probability is much easier than addressing severity – especially if talking about task-based risk assessments (as opposed to during the earlier design phase – when severity is a bit easier to address. However, when it gets to the task risk assessment, it is really a case of trying to manage aspects that couldn’t be designed out – and often, it is the probability that can be addressed… Read more »
Thanks everyone for the comments/feedback (and for confirming that some health and safety practitioners are adamant that severity cannot be reduced). I can see that in some scenarios, we can’t make the hazard less potent. However, if I take an example like the Foodles Production (UK) Ltd prosecution, I can see how even machinery can be made less dangerous. If I was designing the Millennium Falcon doors I could make sure they came down at a leisurely pace, I’d construct them predominantly from soft wood or aluminium rather than steel, I’d have a rubber pad on the bottom and could… Read more »
I believe the point you are missing is that if you fundamentally change part of the process/machinery/substance as a result of the original risk assessment, then the task will need to be reassessed and your risk assessment updated taking into account the changes that you have introduced. At this point severity in your pre-control measures risk rating will be reduced because you are assessing a different process/machinery/substance.
The principle should still be to always reduce the likelihood to as low as possible regardless of the severity rating.
Totally agree Nick. It would appear that people are concentrating purely on the hazard and whether or not it can be reduced as opposed to the risk i.e. quantifying both the likelihood and severity of harm and applying control measures using the principles of prevention in an attempt to reduce both, as far as is reasonably practicable. As mentioned, in many cases it is much easier to reduce the likelihood of harm than the severity (potential outcomes) Yes, we can reduce the severity of harm of a corrosive chemical (the hazard) to the skin through replacing the dangerous with the… Read more »
Dear Steve,
Sorry to involve in your comment .
Could you please explain the way to reduce the severity of risk in the risk assessment process with use of PPE directly.
If you applying direct PPE there is some clause have to full fill.
e.g The selection,use,maintenance and storage{if anything fails(slips and lapses) the severity won’t change}
Moreover PPE is the last resort in the risk assessment process.
Hi Rajesh, This depends very much on the task itself. For example, wearing cut-proof gloves can reduce the severity. I rarely reduce severity in a risk assessment as in the construction industry the task is almost always decided in advance with no opportunity of reducing severity. I have been working on a task today where a void in the 1st floor was covered by timber which was held in place. To carry out the task the timber had to be removed. It was replaced by a smaller piece which was knocked down the void onto the ground floor, near missing… Read more »
A well considered article. Reducing the severity of the outcome is sometimes possible and professional practitioners will always try to achieve this where possible. I had to smile at some of the comments regarding the bleach, It is so easy to get bogged down in these sort of discussions. In the case study covered the use of a bleach to clean the metal was a component of a wider process and it was this risks associated with this process that were being assessed. Substitution of a substance with a less harmful alternative eliminates the original substance from the process and… Read more »
Nick et al, a thought provoking article and comments even if it is an old chestnut. One of the problems with our industry is that the terms we use are interchangeable which often creates confusion and sometimes nothing more than semantics. I would be very surprised if an experienced h&s practitioner could not rationalise the concept of risk applied to risk assessments i.e. severity, likelihood and frequency. Another confusing aspect of risk assessments is all the different types of templates, some with a matrix and some without. If ever there was an industry good cause it would surely include a… Read more »
Wearing a helmet on a motorbike doesn’t reduce the likelihood of falling off the bike and hitting your head. It reduces the severity of the outcome of hitting your head. If you want to reduce the likelihood of falling off your bike and hitting your head then drive a car.
Hope you don’t have adequate idea about the risk assessment process.
First point is that PPE is the last resort in the risk assessment process.
Helmet only protects the specific part (Head) but not whole part of the body and what about to other part of body when accident happens while driving.
Consider the selection(degree of area covered when selecting the Helmet),use,maintenance and storage of PPE.
Expected your valued comment.
I’d argue that using a water based low VOC paint would be far better for health than using high VOC paints. Reducing severity of harm – sorted!!!
You have changed the task which would then require a new risk assesment, and the severity of that would change. The severity of using high VOC paints cannot change
Everyone on this thread is correct because each is speaking to different way of thinking about risk. Taking a point risk for which the outcome is specified (it’s a constant) means risk control can only reduce likelihood. Taking a population of outcomes means risk control can change the distribution of the outcome population. Overall severity (area under the curve) can be reduced. Those using matrices are sometimes using point outcomes and sometimes population outcomes as this thread shows. Interesting and illuminating thread at so many levels. I don’t use matrices. When I need to quantify I use Monte Carlo methods.
Dear Gents; I am really happy to join this fruitful discussion. Many people insist on severity couldn’t be reduced. It is not correct. Techniques of the hierarchy of control help greatly reducing the severity along with reducing the probability as well. Techniques/Technology of Manufacture helps greatly providing products that share reducing the severity of harm. Adequate Safety Management (Administrative control measures) share reducing the severity of harm, too. Adequate HSE Management system components (Manual, plans, programs, procedures) along with the competency of the adhered key persons will result in adequate safety performance that means reducing both probability of hazard occurs… Read more »
Really enjoyed reading this article and everyone’s stance on this key subject. The debates I get into revolve around this in a different way. People send me RAMS for approval and mark down severity with only likelihood affecting controls or sometimes they mark down both with only likelihood affecting controls. I’m all for reducing severity when it can be achieved (And I believe it can and agree with examples in the comments) but there are a lot of people out there writing RAMS with 5 x 5 assessments that just don’t get it.
I can see the logic in each argument however, from my point of view the severity is exclusively linked to the initial problem statement. The severity of harm from being burnt buy concentrated acid will forever be a 10. to mitigate by using a weak acid is not adjusting the severity of the original concern, it reduces the occurrence/likelihood of the concentrated acid causing harm; in this case to zero. On the next round of risk assessments, that original hazard can be removed. The argument is similar for the person falling; the severity remains the same but occurrence goes down.… Read more »
A hazard always remains a hazard hence the severity. The likelihood of your interaction with it reduces the hazard. A shark for example does not change from being a shark to cotton wool. It remains a shark. So the control measures could be to stay on the esplanade, on the beach or in a cage if you want to swim with them. Basically the closer you get to the hazard the more potential there is to be affected by it. The only way to reduce the hazard completely is to not have the hazard, but then there would be no… Read more »
Although I can argue the same that Nick’s example is not so well put by saying the risk identified is no longer the original risk. I can provide a better example. lets say a man is performing work on a tall structure, considering that this man just matriculated and has no work experience and control measures are non existing at this stage. The chances of this man to fall is high, the consequences are fatal, resulting in a high risk rating. now, after implementing control measures, such lifelines, safety harnesses, training, supervision, safety catch nets, SWP & PTO, etc. In… Read more »
Mr. Max ,
Simple logic,
What ever you are taking the preventive measures while assessing the risk it may only reducing the likelihood but REMEMBER there is the foreseeable risk fall from height still existing so that severity will remains same in these case.Or you have to give value ZERO severity.
Thank you
It is not the fall that is the harm. It is the impact. The risk associated with the fall is injury. The potential harm is fatal, maximum severity. You have reduced the potential for this harm with the net. You have not reduced the cause (fall) but have reduced the occurrence of harm. The severity of the impact harm remains maximum, the likelihood of occurrence has been reduced.
Fall from a different height, while all other conditions remain the same, will change the severity of the risk.
amended version as i was unable to change original one!
As a risk manager, professional and academic i love this debate! The examples you have used above are in relation to the Hazard. The hazard remains the same and cannot change and as such the severity calculation within a standard RA is based on a person coming into contact or being directly affected by the hazard. In regards to the risk assessment process, you are measuring the likelihood of an individual coming into contact with that specific hazard. If you change the hazard you change the assessment, because if you don’t, you are comparing apples with oranges. Some assumptions are… Read more »
Hi, Please clarify? You wrote -“If you are calculating S×L 4×4 and then reducing to 2×1 and claiming you have reduced severity to 2 because you’ve changed the bleach. You haven’t used the hierarchy of control” … – How is the act of changing to a less dangerous substance not the act of applying the “substitution” element of hierarchy of control? And also, let’s consider a different scenario :- When you install a fall-net around a highrise building, you are not reducing the likelihood of an unplanned fall event. You are not reducing the “likelihood of there being a consequence… Read more »
So my reference to not using the hierarchy of control is in relation to the risk assessment form that you would use. If you are using the hierarchy of control prior to the risk assessment form then yes you are substituting the bleach, but the form you are now completing and submitting for final appraisal is on new bleach not old bleach. So the severity is on new bleach or in my example a 2. Using your example of a net is correct in that you have reduced the severity of fall from let’s say 100m to 10m due to… Read more »
Collective fall protection such as netting obviously reduces the likelihood of an injury whilst falling but the bottom line is if that control measure failed (loose netting, worn or frayed netting, supports failure etc.) then the severity would be the same, therefore CANNOT be reduced.
Still changing the design in the wider scheme. A case of what constitutes the design. I would consider all aspects so changing the bleach or drop height is actually changing the design because severity related to the previous design concept.
Tiger is a man eater and the severity is fatal. Once, it is caged, the probability of harm comes down. When we talk of Risk reduction measures, we should never distinguish between an aggressive Tiger and an aged old Tiger to reduce Severity. The same is true for high voltage and low voltage electricity, where Severities are different right in the beginning. The severity does not change in a given situation but only probabilities could be reduced to reduce risk.
If the severity is not reduced and only the probability …Please explain how a fall net (let’s say in good condition) when placed around the edge of a multi-storey building only reduces the probabilitiy of the unwanted event, such as a fall. When we talk about risk reduction we cannot talk about the liklihood of the severity being reduced because then it becomes 100% subjective. We talk about reduction in the probability of the unwanted event occuring OR the reduction in the severity (consequences) of the unwanted event. We can’t state that a fall net is reducing the probability of… Read more »
When we use a fall net, we are introducing a layer of protection against an undesirable event(fatality) and this LOP reduces the Overall Risk by reducing the probability. Risk is a product of Severity and probability. Severity with respect to fatality from fall does not change but the consequential risk gets reduced.
Caging a Tiger reduces the probability of the unplanned event to pretty much zero. That is not the case with a seatbelt or fall net …because the likelihood of the unwanted event ….fall or crash …is still the ssame.
Seat belt and fall net are layers of protection introduced to reduce the risk of fatality from impact. Here again, the Severity remains same but the consequential risk gets reduced as the probability of the undesired event(fatality)gets reduced drastically(probability of failure of the Seat belt snapping or failure of the air bag getting inflated and coming in between the steering and the driver) on a sudden crash scenerio .
Great article Nick and brilliant debate, it’s something we have all likely discussed at some point. My view is you can alter both the severity and likelihood it’s simply a matter of what choice of controls you decide. By keeping the same hazard (chemical) and installing controls or altering the work method you can reduce the likelihood, however, if we change the hazard (chemical) we can also reduce the severity. I don’t think there is any science to this just different mind sets.
A risk assessment can reduce severity of outcome by deploying the heirarchy of control. Once you have established that you have reduced your hazard as low as reasonably practicable (ALARP) and you identify your risk assessment form and method of calculation (e.g. 5×5 matrix) and subsequent mitigations. The severity remains the same on the residual calculation. This is because you have, or should have, already reduced the severity to this lowest point. If this happens to be working at 100m high at the edge of a building for example as there is no othr safe way. Then the controls/mitigations reduce… Read more »
I conducted a case study on a school road in London, which had experienced a few vehicle and child collisions over a few years. In order to further reduce risk, the local authority reduced the speed limit to 20mph. This resulted in reduced risk perception in the children, and more incidents occured as a result, but the overall data of incident severity was much lower than previously recorded. An increase in likelihood, and a reduction in severity.