Intro3 understanding the SMIDSY

“Sorry Mate, I Didn’t See You”

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What follows is an investigation into the research papers that look at the collisions that happen between powered two-wheelers and other vehicles at junctions, most often when the rider had the legal ‘right-of-way’. In the UK, these collisions are often referred to as ‘SMIDSY’ crashes, from the apology that many drivers offer to the riders – “Sorry Mate, I Didn’t See You’.

To help you track the references back to those papers, I use the standard system known as a ‘citation’ which gives credit to the author(s) and the original paper. The expression ‘et al’ means that more than one person was responsible for the research.

THE BACKGROUND TO SOBS: It’s long been known that riding a powered two-wheeler (or PTW; – ie, a motorcycle, scooter or moped) carries a high risk of death or injury. Helman et al (2012) in a recent literature review produced by the UK’s Transport Research Laboratory (TRL) states:

“…it is far from controversial to say that motorcycling is the most risky form of mainstream transport per kilometre travelled.”

When I was invited to create an ‘accident prevention’ module for the pilot ‘Biker Down’ course by James Sanderson of Kent Fire and Rescue Service in 2011, there were a range of topics that immediately suggested themselves. Cornering crashes was one. Another was group riding, and I actually did create a presentation based on that issue. But I quickly settled on the infamous SMIDSY collision as the basis for what has become known as the ‘Science Of Being Seen’ or SOBS for short.

Why focus on the SMIDSY? Quite simple. It’s long been believed – both by bikers and by road safety authorities that a particular problem for motorcyclists is the collisions at junctions. Most riders tend to assume the SMIDSY happens when a driver pulls out from the rider’s nearside (that would be from the LEFT in the UK and other countries that drive on the left, but on the RIGHT in the US, France and other countries that drive on the right). But is that actually correct? And does it only happen to bikers?

So the first question to ask ourselves is this: “do motorcyclists really suffer more collisions with cars?”

In a recent paper, de Craen et al (2013):

“…tries to unravel whether – acknowledging the differences in exposure – car drivers indeed fail to yield for motorcycles more often than for other cars. For this purpose we compared the causes of crashes on intersections (e.g. failing to give priority, speeding, etc.) between different crash types (car-motorcycle or car-car). In addition, we compared the crash causes of dual drivers (i.e. car drivers who also have their motorcycle licence) with regular car drivers. Our crash analysis suggests that car drivers do not fail to give priority to motorcycles relatively more often than to another car when this car/motorcycle approaches from a perpendicular angle.”

In other words, in this study from the Netherlands, the crash rate with cars that EMERGE from a side turning is much the same whether the approaching vehicle is a car or a PTW. Cars hugely outnumber bikes on the roads, but that is a surprising conclusion. However, they continue:

“There is only one priority situation where motorcycles seem to be at a disadvantage compared to cars. This is when a car makes a left turn, and fails to give priority to an oncoming motorcycle. This specific crash scenario occurs more often when the oncoming vehicle is a motorcycle than when it is a car. We did not find a significant difference between dual drivers and regular car drivers in how often they give priority to motorcycles compared to cars.”

Remembering that the ‘left turn’ referred to is a right turn in the UK, it should be clear that the collisions where motorcycles are over-represented involved another ONCOMING vehicle turning across a motorcycle’s path when the motorcycle is on the priority road.

Clarke et al (2007) investigated a sample of crashes involving motorcycles in the UK:

“A sample of 1790 accident cases was considered, including 1003 in detail, from UK midland police forces, involving motorcyclists of all ages, and covering the years 1997-2002 inclusive. Significant differences were discovered in the sample with respect to types of accidents involving motorcyclists (and their blameworthiness). There seems to be a particular problem surrounding other road users’ perception of motorcycles, particularly at junctions. Such accidents often seem to involve older drivers with relatively high levels of driving experience who nonetheless seem to have problems detecting approaching motorcycles.”

Junction collisions were further described by Helman et al (2012) in the TRL paper:

“It is widely accepted that one key factor in motorcyclist crashes around the world is the difficulty other road users have in detecting an approaching motorcyclist or correctly appraising their speed and position. This is of particular concern at road intersections, when drivers need to detect gaps in oncoming traffic to make turns either across or into traffic flows. If a motorcyclist is not detected by a car driver in this situation (so-called ‘looked but failed to see’) then this can lead to a manoeuvre that violates the motorcyclist’s path, and a potential crash.”

So to sum up, a significant number of collisions between vehicles generally happen at junctions, motorcyclists are most at risk when the other vehicle approaches from the opposite direction and turns across the motorcycle’s path, the collision is usually the result of the other road user’s actions, and when violating the rider’s right-of-way, the problem for the driver appears to be a detection issue.

And that leads us directly to a second question: “why do drivers fail to detect motorcycles?” And quite honestly, we’re still searching for a definite answer. The fact that a paper entitled ‘Sorry, Mate, I Didn’t See You: A Plausible Scientific Explanation’ could be published as recently as 2006 after more than thirty years of research on the issue should serve as a warning – the problem is complex, and we haven’t got to the bottom of it yet! So to make a start on understanding what goes wrong and what we motorcyclists can do about it, some historical perspective on the research into motorcycle crashes is useful.

Driver looking
A still snipped from a UK road safety information film from the early 2000s.

WHERE IT ALL STARTED: In 1975, the Greater London Road Safety Unit identified PTWs as being over-represented in accidents. Detailed analysis followed and the results indicated that a major contributory factor was that other drivers failed to see the motorcycles in the general street scene. Helman et al (2012) suggest that the 1976 Greater London ‘Right Bright’ campaign that followed:

“… may have been the first road safety campaign specifically designed to encourage riders of powered two-wheelers to improve their conspicuity by wearing bright clothing, preferably of fluorescent material, and by switching on their headlights in daytime. The campaign was extensive, running from August to October 1978, and involved radio advertising (on two London-based stations in the UK), a poster campaign, leaflets distributed through a number of routes (including dealers, garages, colleges, businesses and by London’s Metropolitan Police Service) and give-away items such as combs, pens and key-rings.”

In 1977 a US researcher named Harry Hurt co-authored a report with Dupont. They wrote that:

“the most likely comment of an automobile driver involved in a traffic collision with a motorcycle is that he, or she, did not SEE the motorcycle…”

Within a few years Hurt’s name would become synonymous with research into motorcycle crashes when he put his name to a mammoth study that became known as the ‘Hurt Report’ (1981). It has become a seminal work and you can find it easily online. Based on his research in California, what Harry Hurt found (amongst other things) was that:

“Approximately 3/4 of motorcycle accidents involved collision with another vehicle at an intersection. The driver of the other vehicle violated the motorcycle right-of-way and caused the accident in 2/3 of those accidents and did not see the motorcycle or or did not see the motorcycle until too late to avoid the collision. Most involved passenger cars…”

Just a year or two later on our own side of the Big Pond, Keith Booth looked at 10,000 motorcycle crashes in London. Although I cannot find the original research, he released a report called “Characteristics of Urban Motorcycle Accidents” through the Institute of Motorcycling. Booth’s observation was that in London:

“62% of motorcycle accidents were primarily caused by the other road user. In 2/3 of motorcycle accidents where the driver was at fault, the accident was due to the driver failing to anticipate the action of the motorcyclist.”

In other words, the same crashes were happening in big cities on both sides of the Atlantic. The obvious question was: “why?” Hurt drew much the same conclusion as the earlier GLC study in London:

“The origin of this problem seems to be related to the element of conspicuity (or conspicuousness) of the motorcycle; in other words, how easy it is to see the motorcycle. When the motorcycle and the automobile are on collision paths, or when the vehicles are in opposing traffic, the conspicuity due to motion is very low, if it exists at all.

“Consequently, recognition of the motorcycle by the automobile driver will depend entirely upon the conspicuity due to contrast.

“If the approaching motorcycle and rider blend well with the background scene, and if the automobile driver has not developed improved visual search habits which include low-threat targets (such as motorcycles and bicycles, as contrasted with the high-threat targets presented by trucks and buses) the motorcycle will not be recognized as a vehicle and a traffic hazard exists.”

Note that phrase “entirely on the conspicuity”. It’s going to be important. These accidents are often categorised as ‘Looked But Failed To See’ errors (LBFTS), because the driver claims that they looked in the appropriate direction for conflicting traffic, but did not see the approaching motorcycle.

THE ORIGINS OF RIDE BRIGHT & THINK BIKE: Let’s turn to the search for practical solutions to the SMIDSY. If drivers were colliding with motorcycles that they hadn’t seen because the motorcycle had poor conspicuity, what was the answer?

Crane F

Let’s introduce the concept of ‘visual salience’. Some objects have a distinct perceptual quality which draws our eyes – salience. Saliency is relatively easy to measure by looking relative contrast or brightness. It’s been theorised that the human brain has evolved to detect salience and it does this by processing the visual field BELOW THE LEVEL OF CONSCIOUSNESS.

ONLY when our visual processing system detects something with visual salience does a signal goes to the real-time ‘thinking’ brain, and ONLY NOW does the particular area or object pop up into our real-time consciousness. And only NOW can we give it our attention. ONLY at this point do we become aware that our visual system has detected anything. You could say “out of mind, out of sight”.

It is important to understand this unconscious / conscious split between what’s in our visual field what we are aware of seeing, because this is the fundamental concept underpinning the ‘common sense’ answers to rider conspicuity:

  • RIDE BRIGHT – motorcyclists should make themselves more conspicuous and easier to see (that is, increase ‘visual salience’)
  • THINK BIKE – drivers should look harder for motorcycles

Not too surprisingly, road safety bodies the world over have adopted these two strategies.


THE RIDE BRIGHT CAMPAIGNS: Three possible ways of increasing visual conspicuity were proposed:

  • by increasing the profile of the vehicle, in particular the frontal profile via the mounting of a white fairing (which also provides a place to attach other conspicuity-enhancing devices)
  • by using retro-reflective or coloured materials on the motorcycle as well as on for the motorcyclists’ garments and helmet
  • by using active lighting; suggestions have included day running lights, dipped head lights, additional low-beam lights, high-beam lights, strobes, lights with rotating prisms and many others. Dipped head lights are usually seen as the most practical solution as they are already fitted to virtually all motorcycles

From the mid-70s to the current day, conspicuity campaigns have run all over the world and are still running today – I picked up a hi-vis vest handed out by the local road safety body in Auckland whilst I was in New Zealand in February 2018. Here in the UK, the Highway Code advice to motorcyclists has been to “wear light-coloured or reflective and fluorescent clothing” since 1978. The advice to use “dipped headlights on larger machines” was added in 1987, and by 1999 PTW operators were being told that “dipped headlights might make motorcyclists more conspicuous”. In some places the use of conspicuity aids has been enforced via legislation. In the UK, hi-vis clothing has been a legal requirement for on-road basic training since the introduction of Compulsory Basic Training in 1990 and at least some new riders continue to use it voluntarily after passing the test. Several EU countries including France require day-time lights. Canada and many US states have similar compulsory daylight laws, as do other countries around the world. Whilst the UK has no lights-on rules, new motorcycles in the EU now have no way to turn off the headlight’s low (dipped) beam – the switch has been removed.  But there’s no single policy – there is a mish-mash of voluntary use, coercion and legislation regarding the use of conspicuity aids.

DO CONSPICUITY AIDS WORK: So, what was the result? What happened out on the road? If conspicuity aids worked as billed, we would expect to see a reduction in the number of motorcycle crashes happening at junctions.

After the initial ‘Ride Bright’ campaign in London – and set against a background of increasing motorcycle use in the city – Lalani and Holden (1978) concluded that the results of the campaign were positive:

“Total daylight motorcycle casualties increased by 6-8 per cent,while dark accident casualties rose by 14.9 per cent. Had there been no ‘Ride Bright’ campaign, daylight motorcycle casualties would also have increased by 14.9 per cent (this being confirmed by casualty data trends prior to the campaign for the years 1974-1976). A saving of 8.1 per cent daylight casualties can be attributed to the campaign, or alternatively 570 casualties.”

Although an increase in casualties sounds bad, this study took place at a time of rapidly riding PTW use. So the conclusions actually suggest a positive result. More recently, a number – though not all – studies suggest that in general, riders using hi-vis clothing and DRLs have a lower crash risk than riders who have not adopted these measures. Helman et al (2012) stated in their literature review:

“The majority of early evidence (mainly from the 1970s and 1980s) concerned bright clothing and daytime running lights on motorcycles. When considering the weight of evidence, both seem to be capable of improving conspicuity, when this is measured in terms of detection (under search and attention conspicuity conditions), and when measured in terms of a behavioural response (such as size of gap accepted in front of a given motorcycle). The majority of studies covered in this review support this conclusion…”

But there’s a problem. Data from the Department of the Environment, Transport and the Regions (DETR) published in February 1999 showed that in 1998 – twenty years after the ‘Ride Bright’ campaign and Hurt’s work, and well over a decade after Booth – collisions involving a motorcycle and another vehicle STILL accounted for two-thirds of all motorcycle accidents. Let’s move forward to 2004 and a UK-based ‘In-Depth Study of Motorcycle Accidents’. The authors reported that in about 2/3rds of crashes where the rider was not to blame, the driver failed to see a rider who was in clear view and who was often seen by other road users. In about 12% of these cases, the driver failed to see the motorcyclist even though s/he was wearing high visibility garments or using daytime running lights.


If we look outside the UK but still within Europe, the pan-European study ‘Motorcycle Accidents In-Depth Study’ (or MAIDS for short), first released in 2004 then updated in 2009, it was found that just over half of all crashes involving a powered two-wheeler (ie a motorcycle or moped) took place at an intersection. 60% of these collisions were with a car, 72% of the accidents took place in urban areas, and in 50% the car driver was to blame. And the important conclusion was that in over 70% of the collisions that were the result of an error on the part of the other driver, the collision involved a failure to see the a motorcycle.

Whilst we cannot see if there has been a reduction in crash NUMBERS, what those percentage figures – 66%, 66% and 70% – reveal is that in terms of accident DISTRIBUTION, nothing much has changed. We haven’t seen a genuinely significant reduction in the proportion of junction collisions where drivers do not see the motorcycle. I don’t seem to be the only one to have spotted this. In a study involving a simulator, Sager and his colleagues noted in 2014:

“much previous research has focused on motorcycle properties, such as size, shape, and color to explain its inconspicuousness… Much of the motorcycle safety research conducted since has focused on making motorcycles more conspicuous, generally through various lighting treatments such as headlight modulators, additional lights, and bright reflective garments…

“There is some debate, however, regarding the effectiveness of these measures…it has been suggested that the problem may not be one of conspicuity at all…collision statistics remain largely unchanged, suggesting that the issue may not be related solely to the motorcycle’s static properties.”

If collision statistics remain unchanged, it’s hard to see that ‘Ride Bright’ conspicuity aids for riders or ‘Think Bike’ campaigns aimed at drivers have had the results that were proposed for them. Espié in the foreword to the book ‘Increasing Motorcycle Conspicuity – Design and Assessment of Interventions to Enhance Rider Safety’ states that:

“several approaches may be proposed to increase the PTW/rider conspicuity… however many proposed solutions were not supported by scientific evidence.”

NEARLY ALL DRIVERS SEE NEARLY ALL BIKES: This is a good place to make the point that whilst SMIDSY collisions may dominate the accident statistics for motorcyclists, a moment’s thought should tell us that for every ‘Looked But Failed To See’ event that results in a ROWV and a subsequent collision, an untold number of drivers actually successfully spot motorcyclists and do NOT turn in front of them. If that were not true, the average rider would never complete his or her journey! Crundall et al (2012) recognise this. The report says:

“Despite the over-representation of motorcyclists in crash statistics, by far the majority of motorcycle journeys do not result in a crash. Car drivers do not want to have a crash, and it is reasonable to assume… that in the majority of cases drivers will respond appropriately to motorcycles. It is the occasional situation that we are concerned with, where attention might lapse, or judgement is made too hastily, which may result in a crash.”

I personally have been drawing attention to this specific point for a number of years. When considering collisions between motorcycles and cars, it’s important to understand that the vast majority of drivers will NEVER precipitate a ‘Looked But Failed To See’ collision. That has serious implications for ‘Think Bike’ driver education and deterrence programmes.

TERMINOLOGY: Although we’ve now seen three of the terms in common use:

  • SMIDSY (Sorry Mate I Didn’t See You) to describe the collision
  • ROWV (Right Of Way Violation) to assign fault
  • BFTS (‘Looked But Failed To See’) to explain just how the ROWV occurred

…it’s worth noting at this point that despite decades of research and hundreds upon hundreds of studies, there has been little attempt to create a standard lexicon (that is, a specialised vocabulary) to accurately describe these collisions.

What’s more, studies have been performed from both the ‘drive on the left’ (for example, in the UK, Australia and New Zealand) and from the ‘drive on the right’ (eg, the EU and USA) perspectives. When driving on the left, a turning on the nearside is on the motorcyclist’s LEFT. For studies from other countries such as the rest of the EU and the USA, this is reversed and the turning on the nearside is on the motorcyclist’s RIGHT. Whilst the scenarios are a mirror image, few authors make it absolutely clear whether a drive on the left or a drive on the right regime is the subject of their study. If a driver is stated to have ‘turned right’, the actual manoeuvre depends on which side of the road the vehicles are driving. The answer can usually be determined by the location of the study but is rarely explicit.

Another lack of clarity arises when studies use expressions such as the vehicle ‘turned right’ or ‘turned left’. Even when clear which side of the road the driver is driving on, this is an inadequate description of the manoeuvre. From where, to where? Whilst the two collisions we are most concerned about involve EITHER a vehicle that emerges and turns across the rider’s path from an opening at the rider’s nearside OR an oncoming vehicle that turns across the rider’s path towards an opening at the rider’s nearside, a moment’s thought should show us there are four possible ‘turned right’ manoeuvres that could be performed at a crossroads when driving on the left – a driver could:

  • emerge and turn right across the rider’s path from the nearside – the side of the road nearest the rider
  • emerge and turn right into the rider’s path from the offside – the side of the road furthest from the rider
  • slow and turn right into a side turning whilst leading – moving in the same direction ahead of the motorcycle
  • slow and turn right across the rider’s path whilst oncoming – approaching from the opposite direction

Whilst the manoeuvre can usually be inferred from the context, it’s not always the case. I will use the terms ‘nearside’, ‘offside’, ’emerging’, ‘oncoming’ and ‘leading’ be applied to define the manoeuvres more precisely. It’s worth noting that road layouts and priorities exist which have different priority systems, even though the layout is likely to cause specific problems. The roundabout is one example. The four-way stop is another. In much of Europe the system of ‘priority to the right’ exists.

There has been at least one attempt to standardise the understanding of these collisions. In a summary report prepared for the Department for Transport: London, Crundall et al (2008) proposed a framework on which to base understanding of the work that has been carried out on these collisions which related “attitudes, knowledge and skills/strategies to three behaviours”. They proposed three questions that research needed to ask:

  • does the driver look at the motorcyclist?
  • does the driver realise that it is a motorcyclist?
  • does the driver correctly decide whether the motorcyclist poses a hazard?

Over the next dozen pages, I’ll be looking in detail at the research that has been carried out into these questions.


Since you’re here, I’ve a small favour to ask. If you feel able to make a small donation to the upkeep and continued development of SOBS, why

But before you do, I’ve a small favour to ask.

Researching, documenting and constructing the ‘Science Of Being Seen’ site has, as you’ve probably realised, taken many hours of hard work. I believe the information here is of immense value to each and every motorcyclist, to help understand and defend against the most common crash wherever you are in the world.

The content is not hidden behind a paywall; access is entirely free.

But to keep working on the SOBS project, I need your help to continue to improve the content and keep it updated with the latest research. All work on this project is carried out in my own time and I don’t have sponsors. If you feel able, a small donation to the upkeep and continued development of SOBS would be greatly appreciated.


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What to read now…

Now, you have a decision to make. There are two ways forward.

You can work your way through the sequence of pages, in each of which I have investigated in-depth the research on each issue connected with motorcycle conspicuity and visual perception and how the problems uncovered relate to the SMIDSY collision. If you’re interested in the technicalities, this is the way to go…

Continue your journey to the next page…


You can skip the detail and head straight to the discussion page, and then read the posts which suggest  how to use successful conspicuity strategies. If you just want quick answers, this is your best option – and you can always come back to the in-depth investigation later.


Clarke, D. D., Ward, P., Bartle, C. & Truman, W. (2004). “In-Depth Study of Motorcycle Accidents”, Road Safety Research Report 54, Department for Transport.

Clarke, D. D., Ward, P., Bartle, C., Truman, W. (2007). “The role of motorcyclist and other driver behaviour in two types of serious accident in the UK”, Accident Analysis and Prevention, 39, 974-981.

Crundall, D,. Clarke, D., Ward, P. & Bartle C. (2008) “Car Drivers’ Skills and Attitudes to Motorcycle Safety: A Review” Road Safety Research Report No. 85 Department for Transport: London. School of Psychology, University of Nottingham

Crundall, D., Crundall. E., Clarke, D. &Shahar, A. (2012) “Why do car drivers fail to give way to motorcycles at t-junctions?”, Accident Research Unit, School of Psychology, University of Nottingham, Nottingham NG7 2RD, United Kingdom

de Craen, S., Doumen, D. & van Norden, Y. 2013 “A different perspective on conspicuity related motorcycle crashes”, Accident; analysis and prevention 63C:133-137 SWOV Institute for Road Safety Research

Helman, S., Weare, A., Palmer, M. & Fernandez-Medina, K. (2012). “Literature review of interventions to improve the conspicuity of motorcyclists and help avoid ‘looked but failed to see’ accidents”, Published Project Report PPR638, Transport Research Laboratory Road Safety Group.

Hurt, H.H., DuPont, C.J. (1977), “Human Factors in Motorcycle Accidents”, SAE Technical Paper 770103, doi:10.4271/770103.

Hurt Jr., H.H., Ouellet, J.V., Thom, D.R., (1981). “Motorcycle Accident Cause Factors and Identification of Countermeasures, vol. 1”, US Department of Transportation, National Highway Traffic Safety Administration, Washington, DC

“In-Depth Study of Motorcycle Accidents”, (2004), Road Safety Research Report 54, Department for Transport.

Lalani, N & Holden, E. J. (1978) “The Greater Londorn ‘Ride Bright’ campaign; its effect on motorcyclist conspicuity and casualties’ Traffic Engineering and Control, Aug-Sep 1978 pp 404-6

“MAIDS – the Motorcycle Accidents In Depth Study” (2004 updated ‘09). ACEM (European Motorcycle Manufacturers Association).

Sager, Bertrand, Yanko, Matthew R., Spalek, Thomas M., Froc, David J., Bernstein, Daniel M., Dastur, Farhad N., (2014) “Motorcyclist’s Lane Position as a Factor in Right-of-Way Violation Collisions: A Driving Simulator Study,” Accident Analysis and Prevention 72 325-329.

White, M., “Sorry, Mate, I Didn’t See You: A Plausible Scientific Explanation” Safety Strategy Section, SA Department for Transport, Energy and Infrastructure Australasian Road Safety Research, presented at Policing and Education Conference October 2006

Last updated:

Monday 16 August 2021 – minor edit for clarity and structure
Tuesday 30 April 2019 – minor edit for clarity, typos corrected
Friday 14 December 2018 – added dates for advice about conspicuity aids added to the Highway Code, added de Craen et al reference
Friday 23 November 2018 – typos corrected, minor edit for clarity, improved explanation of salience

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