SUMMARY – to be conspicuous, we need to present a recognisable shape… although motion draws attention, we still need to recognise what moved… disruptive camouflage breaks down shapes to hinder recognition… clothing and bikes with multiple colours create a form of disruptive camouflage… many garments sold as ‘hi-vis’ are disruptive patterning… single colours produce a strong silhouette and are likely to be more rapidly recognised by drivers…

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Previously, I pointed out that if hi-vis clothing is to make motorcyclists more conspicuous, then it has to be able to do two things:

• to create a strong colour / brightness CONTRAST against the background behind the bike and rider
• to create a SHAPE that is instantly recognisable

You might be wondering why shape is important – after all, the way hi-vis clothing has been promoted suggests that wearing something bright is enough. Unfortunately, the answer is – as you have probably guessed – more complicated than that.

I also pointed out that outside of trials, there’s limited evidence for its real-world success. Why might that be? Possibly we’re asking the wrong question. Research into motorcycle conspicuity virtually always starts from the assumption that PTWs are hard to see, but a moment’s thought will demonstrate that this an almost entirely faulty assumption. The vast majority of motorcyclists ARE SEEN by the vast majority of drivers. If that were NOT the case, we’d never make it past the end of our street!

Unfortunately, thanks to that faulty starting point, research has focussed almost entirely on asking “how can we make a motorcycle and rider stand out?” Given the limited success of conspicuity aids to date, I think a pair of far better questions to start with would be: “what makes a motorcycle and rider INCONSPICUOUS?” And “why is it that PTWs OCCASIONALLY turn out to be invisible?”

Why are these better questions? Because understanding why something DOESN’T happen is often a better route to solving the problem.

Let’s review what we know and start by thinking about camouflage. Camouflage is widely used in the natural world. It breaks down shapes to avoid detection by predators and prey alike. And of course it’s used on the battlefield. The simplest camouflage strategy is simply to make the animal or object in the foreground match the background so that they blend. ‘Background matching’ was described as long ago as the 1890s and was in use well before that – in contrast to the red tunics and white crossbelts of the conventional infantry uniform, the Rifle regiments at the time of the Napoleonic wars wore an olive green outfit. This is to all intents and purposes the contrast issue I talked about previously.

However, simply matching the background often leaves an object’s outline unbroken and detectable, so much camouflage is more complex and relies on visual disruption. Even when movement or light attract our attention to look in the right place, we still have to make sense of what we’re looking at. We have to detect recognisable objects in the visual field… and sometimes we don’t see objects that are clearly capable of being seen. So that is what’s so important about a recognisable shape. The side-on profile below is unmistakably a motorcycle.

Let’s quickly review how the brain processes incoming data from our senses – eyes, ears, touch (but not smell – that is processed in the brain’s emotional centre). Without some kind of filtering, this flow of data would be overwhelming – far more than our conscious brain could cope with.

So there’s a ‘gatekeeping’ mechanism – the ‘reticular activating system’ (RAS) – which decides which pieces of information can be stripped out of the data stream and safely discarded and which are important and should be passed to the real-time part of our brain. The important point to understand is that it’s this stripped-down data fed to our conscious brain which provides our awareness and creates our ‘world view’.

So an obvious question is “what gets through the filters?” Sexual signals and anything that threatens harm always get through. Evolution has wired us to respond to these. Information that is relevant also gets through – our name in conversation on the far side of a noisy room passes the filters. Movement, flashes of light and bright colours are ‘visual attractants’ which draw our attention.

Now, back to shape. Once movement or light have drawn our attention, the brain relies heavily on a ‘shape-detection’ system. How do we know that? Because camouflage which breaks up shape is so effective at hiding things that don’t want to be seen.

Many fish and animals employ ‘countershading’ where the brightly-lit upper surfaces of the body are more darkly pigmented than the less well lit lower areas. Deer are good examples (you can also see it in the tiger and giraffe) and the result is a ‘flatter’, more uniform body colour which creates a lack of depth.

More complex is ‘disruptive colouration’. In essence, the animal’s pattern of colours does not coincide with the contours and outline of the animal’s body creating false corners and edges not corresponding to any identifiable feature of the animal. This ‘surface disruption’ is extremely common. Zebras, which are herd animals, present a highly confusing visual image when together, which may prevent the predator from singling out one particular animal within the herd. Giraffes not only blend well with their environment, but break up their outline with patches. Tabby cats are another example of disruptive colouration. What’s not so obvious – at least, until you look at a tiger with its hi-vis bright orange stripes – is that the visual disruption can be created by colour patterns that do NOT match the background.  Out in the open, a tiger is relatively easy to see, but in its natural habitat where the light intensity varies from bright sunlight patches to deep shade, it will still vanish. Where apparently conspicuous markings create camouflage, this is termed ‘disruptive contrast’.

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Another approach is to employ patches at the visible edge of the body to reduce the likelihood of it being detected. This is known as ‘marginal patterning’. The random spots on the giraffe help achieve this regardless of viewing angle. Many moths have marginal patterns on the wings. You might be thinking that moths on trees aren’t motorcycles on the street, but the basic task of identifying a shape is the same. Fraser et al (2007) looked at how the edge disruption created by marginal patterning affected the ability of human subjects to detect the moths:

“…we conducted controlled trials in which human subjects searched for computer-generated moth images presented against images of oak trees. Moths with edge-extended disruptive markings survived at higher rates, and took longer to find, than all other moth types, whether presented sequentially or simultaneously.

In short, moths with edge-extended disruptive markings took longer to find because the markings at the edges of the wings ‘break up’ the silhouette. A few years on and another team revisited the problem, but used eye-tracking hardware. Looking at moths that had both marginal patterning AND a colour that created a contrast with the background, they found that:

“the number of edge-intersecting patches on a target reduces the likelihood of it being detected, even at the expense of reduced background matching. Crucially, eye-tracking data show that targets with more edge-intersecting patches were looked at for longer periods prior to attack, and passed-over more frequently during search tasks. We therefore show directly that edge patches enhance survivorship by impairing recognition, confirming that disruptive coloration is a distinct camouflage strategy, not simply an artefact of background matching.”

Once again, we have to remember that ‘survivorship’ implies that the moths with the edge patterns were not detected. The eye-tracking showed that the subjects looked at moths with a distinctive background colour but thanks to the marginal patterning, they couldn’t determine easily if what they were looking at was indeed a moth, and often decided it wasn’t and passed onto the next object.

So we do know that there are a range of strategies that animals employ to evade detection and of course disruptive patterns work as camouflage for the military too. Dazzle camouflage was used in WW1, and was first proposed to the Royal Navy by a zoologist! The illustrations of the ship are taken from the 1922 edition of the Encyclopedia Britannica, published just after the end of the war.

The principles were further described by Hugh Cott in a 1940 book called ‘Adaptive Colouration in Animals’. He introduced ideas such as ‘maximum disruptive contrast’ where streaks of boldly contrasting colour will – counter-intuitively – make animals or military vehicles less visible by breaking up their surfaces and outlines:

“…for effective concealment, it is essential that the tell-tale appearance of form should be destroyed… the function of a disruptive pattern is to prevent, or to delay as long as possible, the first recognition of an object by sight… irregular patches of contrasted colours and tones … tend to catch the eye of the observer and to draw his attention away from the shape which bears them.”

He criticised attempts at camouflage early in WW2 for failing to grasp the principles:

“…at close range objects properly treated will appear glaringly conspicuous. But they are not painted for deception at close range.”

Perhaps surprisingly, I’m not aware* of research focusing on the difficulties of detecting motorcycles, just research that assumes they are hard to see and proposes solutions. But once we apply these principles of animal and military camouflage, and knowing human vision can be confused by the markings on a moth then it’s a reasonable assumption that colours on motorcycles and clothing also need to avoid edge patterning and disruptive colouration. The implication is that use of patches and stripes of bright colours on jackets and bikes are likely to make it harder rather than easier for the driver to detect the motorcycle. Finnish motorcycle police use blue jackets with white helmets on a white machine with blue flashes. Could this act as disruptive camouflage?

(* if you do know of any, please let me know and I’ll update this section.)

Here’s an extreme example. It’s the Kent Fire and Rescue ‘FireBike’, used for road safety engagement purposes. The red and yellow ‘Battenburg’ colour scheme appears vibrant in the photo, but the small blocks of contrasting colour add extra edges and corners, and potentially serve to break up the outline of the bike. In essence, we’re creating a picture puzzle that the brain has to reassemble from the parts.

You might argue that recognising the bike is easy enough, despite the disruptive camouflage. But when riding, the background behind us is constantly changing and just as the tiger and giraffe are camouflaged, so multi-coloured stripes and patches of colour are likely to make us harder – not easier – to spot. Ironically, a lot of the research on the effectiveness of hi-vis colour schemes like this ‘Battenburg’ pattern has been carried out by the emergency services themselves!

The same applies to clothing. Here’s a side-on view of my track leathers – stripy red, white and black – and blue/grey helmet. Even if the bike is a solid colour, the leathers break out my own outline.

Of course, it’s not just track leathers that are multi-coloured. Take a look at the typical range of garments offered for sale as conspicuity aids for motorcyclists, and think about them in the context of what we now know about disruptive camouflage patterns. Here’s the front-on view of a typical jacket.

Notice the disruptive edge patterns where patches of yellow and black alternate along the sleeves up to the shoulders. Notice the the disruptive colouration of the yellow stripes down the otherwise black chest. If the research on moths does hold true for motorcycles, it’s likely we can achieve a better detection rate by avoiding clothing that produces different patches of colour at the edges. The more solid our silhouette, the more help we give the driver, and – in theory at least – the more effective our conspicuity aids are likely to be.

Here’s another hi-vis garment to look at. Aside from the fact that most of the hi-vis material is obscured by the top case, in effect what is visible are two horizontal yellow stripes either side of a black stripe, with vertical silver stripes. Will our visual processing system make any sense of them?

Now, you might be saying “but I can see this bike perfectly clearly”. Remember the words of Cott; “at close range objects properly treated will appear glaringly conspicuous. But they are not painted for deception at close range”. Remember too that you’re looking at a static scene in a photo – the motorcycle isn’t moving and you have plenty of time to study it. In real life, the motorcycle be moving across a constantly-changing background, at a changing distance. And rather than staring at it, we’ll be monitoring events happening right across our riding or driving environment – we’ll only be looking in the right direction for brief moments.

The failure to consider camouflage techniques may account for the relative lack of success of ‘anti-background matching’ hi-vis clothing in preventing ‘looked but failed to see’ collisions. It’s possible the disruptive camouflage effect created by multi-coloured bikes and bright patches on clothing explains some incidents where the rider reported: “the driver looked right at me and still pulled out”. They looked, the RAS tried to make sense of the incoming visual data, failed to recognise anything, then passed on to other more recognisable vehicles. A personal observation is that nearly all vehicles around us are a single colour and present a much stronger silhouette with minimal disruptive patterning.

It’s not just visual perception that affects motorcycle detection. Hills, back in 1980, noted that most conspicuity research to that date had neglected to consider the EXPECTATIONS of the observer. Our expectations are at least partly based on what we encounter most frequently (the ‘prevalence’ effect mentioned previously) and ‘semantic meaning (what we’re interested in) In the UK at least, PTWs are outnumbered significantly by cars and most drivers are not motorcyclists and not interested in motorcycles. Here’s a second consideration. When tasked with drawing a motorcycle, the vast majority of us will draw a side-on view. Yet that’s NOT the aspect of the bike that a road user will see when a bike is approaching their viewpoint at a junction – what they’ll see is the head-on view illustrated below. So it could well be that a disconnect exists between a driver’s mental image of a motorcycle, the picture that’s held in mind for shape recognition, and what they actually see. Although I haven’t found any research evidence for this theory, it seems plausible.

But we are all pedestrians. Although it’s well-known that our brains are quick to perceive human faces, we’re usually too far off (and hidden within a helmet) so it seems unlikely we can exploit this, but it appears humans are also quick to perceive the top half of the human torso. Take a look at the two silhouettes below.

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Note how similar the frontal outline of ‘bike and rider’ is to that of a person. If we ‘fill in’ the rider’s silhouette in a single colour and avoid disruptive marginal patterns, it creates a human-like shape. It’s plausible that a rider using clothing that matches the machine’s colour and creates a solid human shape will be more reliably detected than a rider relying on clothing with hi-vis flashes. Have we any evidence for this? You’ll recall that on a bright sunny day, research has shown that a black-clad rider on a black motorcycle turns out to be most conspicuous. Knowing what we do about camouflage and human perception, it may be that the single black colour – with no edge patterning or internal disruption to break up the silhouette – also produces a strong human-like shape. It’s no coincidence my own fair-weather, daytime-riding kit for my black motorcycle is black too!

It’s likely that a SINGLE matching colour – not necessarily a hi-vis colour – for bike and rider (ideally including helmet) will also give a solid frontal silhouette and emphasise our human shape. The motorcycle in the photo is a plain red, and matched reasonably well by the orange hi-vis vest. There are still disruptive edge effects from the jacket sleeves (a hi-vis jacket would have been better) and the black helmet, mirrors exhaust and tyres, but it’s a much more coherent and human-looking colour scheme than most! That’s why when I switch to my red motorcycle, I have a red over-jacket. (Unfortunately, I don’t have an outfit for the blue bike!)

If you have a grey bike, then consider a grey riding suit. Take a look at the bike below – the riding suit, top case, side case lids and fairing (seen from the front) are all a similar shade of grey and the helmet is white. Although not hi-vis colours, and a shade that suffers some background matching with the road surface and the rocks at the side of the road, the single colour preserves the distinctive shape of ‘bike plus rider’.

If you want to use hi-vis, apply the same thinking. Steer clear of jackets with hi-vis flashes but aim for solid colours. And why spend cash on a tabard when a sleeved over-jacket costs barely more money? Have another look at that rear view of the BMW and notice how the top case hides most of the vest. Had the rider been wearing a sleeved hi-vis jacket, the full sleeve would be visible. Sleeves not only avoid the disruptive edge pattern effect but can be see from angled and side-on views, as well as around fairings, passengers and top boxes. Compare the side-on effectiveness of the sleeved hi-vis and the tabard worn by the two riders. It’s no contest – the jacket with the sleeves stands out. (The rider in orange is Keith Wheeler, who’s one of the Biker Down presenters in Buckinghamshire, practicing what we’re preaching.)

In particular, avoid clothing with multiple-coloured hi-vis elements. It’s not ‘hi-vis for all environments’, you should now see it acting as disruptive camouflage. Have another look at this MCN article promoting hi-vis clothing. Notice how the mismatch of bike and garments not only blends with the background but serves to break up a solid silhouette.

And last, and in some ways most important of all, never forget that conspicuity varies on a metre-by-metre basis and is only ever a passive aid. Whether we show up depends on the background, and even if we do pop into the driver’s consciousness, we still rely entirely on the other road user making a decision to keep us safe.

Do you really want to rely 100% on that? I certainly don’t.

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References:

Fraser, S., Callahan, A., Klassen, D. and Sherratt, T., N. (2007); “Empirical tests of the role of disruptive coloration in reducing detectability” Proceeding of the Royal Society biological sciences 22 May 2007.DOI: 10.1098/rspb.2007.0153

Hills B.L., (1980) “Vision, visibility and perception in driving”, Perception 3: 434–467

Tyrrell R.A, Wood J.M., Owens D.A., Borzendowski S.W. & Sewall A.S,, (2016) “The conspicuity of pedestrians at night: a review”, https://doi.org/10.1111/cxo.12447

Webster, R., J., Hassall, C., Herdman, C., M., Godin, J-G., J. & Sherratt T., N. (2013) “Disruptive camouflage impairs object recognition” Royal Society biology letters DOI: 10.1098/rsbl.2013.0501

Last updated: 

Monday 1 May – minor edit for clarity
Thursday 17 January 2019 – added photo of rider in orange sleeved hi-vis jacket
Sunday 18 November 2018 – added information about human silhouette and frontal aspect of motorcycle

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Photo credit Paul Townsend
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