SUMMARY – it’s long been recognised that a dipped headlight is not the most effective day-riding light… making the bike stand out has become a more difficult problem now cars also have day running lights… an effective DRL has to work under multiple conditions… DRLs are most effective at dawn and dusk but less effective in daytime conditions of bright sun… single headlights offer poor help to drivers in judging speed and distance… but DRLs also have to provide a ‘visual signature’ so drivers realise they are seeing a motorcycle and drivers are quick to recognise single headlights as belonging to a bike… twin lights may be mistaken for a car… the ‘triangle of lights’ is ineffective in terms of daytime conspicuity but help drivers judge speed and distance more accurately… unusual lights risk not being recognised as being fitted to a PTW… like hi-vis clothing DRLs are not ‘fit and forget’…
Ever since investigators first looked at the role of conspicuity in motorcycle collisions, it’s been assumed that our headlights would perform as an effective day riding light (DRL). But last time we saw that though there is evidence that a proportion of ‘looked but failed to see’ collisions could be prevented by dipped headlights, the benefits are nothing like as clear-cut as motorcyclists have generally been led to believe. Significantly, it’s not just the most up-to-date studies that question the effectiveness of the dipped headlight as a DRL. As long ago as 1985, Donne & Fulton were proposing twin running lights as superior to a single headlight, and in recent years there have been more radical proposals to enhance motorcycle conspicuity with complex lighting schemes. In the TRL literature review for the Motorcycle Safety Advisory Council (MSAC) in New Zealand, Helman et al (2012) concluded:
“the most promising intervention type (and the one on which there is least work in real-world settings) would appear to be physical changes to motorcycle lighting. These could be configurations that lead to greater contrast with the background (especially differentiation of motorcycles from surrounding traffic with lights – for example differently coloured lights that stand out from the white lights typically see on cars).Alternatively they could utilise additional lights to increase the visual ‘surface area’ of the bike and therefore help not only with detection but also with time-to-collision estimation. Such interventions also have the benefit of being preferable to high visibility and reflective clothing to motorcyclists (based on the small amount of work done on this topic) meaning that such interventions are more likely to be used by motorcyclists, and thus have a chance to be effective.”
But before we look at some of those suggestions, let’s try to understand why the standard low beam headlight seems to have been largely ineffective as a DRL.
There are several possible reasons.
- the first research asked the wrong question and tried to solve the wrong problem
In the section on hi-vis clothing and the need to present a sharply-defined shape to aid detection, I suggested that since it’s been broadly assumed bikes are hard to see, research into motorcycle conspicuity has focused on the wrong question and tried to find ways to make a motorcycle and rider stand out. I suggest we should be asking “what makes a motorcycle and rider INCONSPICUOUS?” to gain a fuller understanding of the issue.
- the conspicuity issue is more complex than can be solved with a low beam headlight
As with hi-vis clothing, an effective DRL is trying to satisfy multiple conditions. Drivers have to see the light, realise it’s a bike and work out how far away it is and how fast it’s moving:
- at a range of distances at both urban and rural speeds
- across a wide angle ahead of the motorcycle
- in urban and rural environments
- across a range of daytime lighting conditions from bright noonday sun through gloomy days to dusk
- at night
- and it mustn’t produce undue glare which could hinder the vision of other road users
The primary role of a motorcycle headlight is to light the rider’s path at night, light scattered away from that path is wasted in terms of night riding. In consequence, both high and low beams of the headlight are designed to project light that is tightly-focused ahead of the machine. A secondary consideration is that low beam (sometimes termed a dipped headlight) should avoid dazzling oncoming drivers. In consequence, a motorcycle’s low beam is compromised in the DRL role. Firstly it fails to project a wide-angle beam – the motorcycle’s DRL is only likely to be detected by other motorists when the PTE approaches at an angle of 30 degrees or less to the driver’s line-of-sight. Secondly, the requirement to avoid dazzle means that the beam is angled beam below the line-of-sight of oncoming drivers. In short, low beam headlights were not designed to be used in the DRL role.
Nevertheless, some ‘light scatter’ always escapes the lens and can be seen ahead of the bike, so over what kind of range might a dipped beam be effective? Paine et al (2005) estimated the effective range of a low beam halogen headlight to be approximately 100 metres on a bright, but not necessarily sunny day. As a 1991 road design handbook recommends lines-of-sight at junctions should be 80 metres where the speed is 40 kph (25 mph). If you recall earlier articles, you’ll remember James Ouellet calculated the motorcyclist’s ‘at risk’ zone as being within three seconds of a junction. At 30 mph (50 kph) that’s around 40 metres. So if there’s any link between adequate lines-of-sight and the range of the dipped beam, then it should prove adequate at urban speeds. But if we double our speed, we quadruple our stopping distance. At 60 kph (37 mph), the recommended line-of-sight is tripled to 120 metres, which Paine considers beyond dipped beam’s effective range. Although other evidence suggests that dipped headlight DRLs are more effective out of town, the implication is that we’re soon beyond the limit of dipped beam’s effective range as speeds rise.
There is also evidence that at lower ambient light intensities – for example, as at dawn and dusk – detection, the distance at which the PTW is detected and the size of the gap ahead of the motorcycle into which the other driver is prepared to turn, are all improved by DRLs over 1,600 candela. However, as the ambient light intensity increases to full daylight, the benefit seems to drop off.
- drivers must recognise they are looking at a motorcycle
Once seen, DRLs have to provide a ‘visual signature’ which allows drivers to realise they are looking at a motorcycle rather than another vehicle. One advantage of a single white headlight was that it was likely to be rapidly identified as belonging to a motorcycle.
- drivers must be able to make an accurate time-to-collision calculation
But as we know, it’s not just about seeing a motorcycle to avoid the ‘looked but failed to see’ error. Once an approaching motorcycle has been recognised, a driver still has to correctly judge its speed and distance. So DRLs must also allow an accurate time-to-collision calculation. Single dipped headlights (or a pair of headlights positioned close together) have been implicated in the ‘looked, saw and misjudged’ error. The ‘looked but failed to see’ and the ‘looked, saw and misjudged’ errors are NOT the same, and an effective defence against one may not solve the other. Paine et al (2005) references another study from 2003 by Rumar (which I have not yet been able to track down) and states that:
“Rumar notes that a single headlamp does not provide adequate distance information… This observation by Rumar, combined with the recent studies of motorcycle accidents where most motorcycles had headlights illuminated in the daytime, indicates that single low-beam headlights might not be particularly effective as motorcycle DRLs.”
Some authorities have noted this. The Minnesota Office of Traffic Safety states in a web page of advice that: “the smaller size and single headlight on the motorcycle make it more difficult for other drivers to judge a rider’s speed and distance”.
- the problem has not stood still
One concern is that early work dates from as long ago as the 1970s. With large motorcycles few and far between at the time, those studies tended to focus on small capacity machines. Since then, motorcycles and the environment in which we ride them have both changed significantly. Today, the average motorcycle encountered by a modern driver in the UK is physically larger. Even smaller capacity machines are often more imposing than the kind of machine in use at the time of the early studies. Thanks to the fairings – something virtually unknown when the early research was carried out – the frontal aspect has changed.
Even the headlights are not the same. In early studies a typical headlight on a small bike would have been round and only 5″ (125mm) or 6″ (150mm) in diameter. Only the biggest machines had bigger 7 ” headlights. At the same time, the feeble 6v 25w or 35w bulbs were dim and barely provided enough illumination to see the way ahead on a dark road. The lens design was poor and scattered light all over the road – dazzling oncoming drivers was not an issue on the mid-70s 125cc motorcycle I learned to ride on! Compare the headlight lens of a modern equivalent which could be fitted with a pair of bright and tightly-focused LED lights. In an article exploring the development of retro-reflective materials, Lloyd (2008) explains how the development of improved reflective road signs through the 1980s was driven by:
“…the refinement of car headlight design which now directed more light down onto the road surface but, as a consequence, reduced the light available to illuminate road signs”
If modern low-beam lights are less effective at illuminating road signs, it seems highly likely that they would be less effective in the DRL role. I’d argue that the results of older studies or data sourced from countries with large fleets of relatively small, relatively old-fashioned motorcycles should only be accepted with caution. It would be instructive if a fresh study was to investigate the light output from older machines like my Honda 125 with the low beam lights on modern machines, in order to compare their function as DRLs. Unfortunately, I know of no such study.
At the same time, the riding environment in the UK has changed dramatically. The motorway network has grown and urban areas have expanded into previously rural environments. Vehicle usage has changed. In the UK, the number of cars and the miles they travel have grown significantly whilst motorcycle numbers are way down from their early 1980s peak. Recreational riding on larger capacity motorcycles has grown Larger capacity motorcycles are more frequently for recreational riding, and commuter use has dropped away. One very recent change in the UK is the sudden explosion in fast-food delivery scooters which pose a new problem in urban areas, particularly at night and in poor riding conditions.
And there’s one other highly significant change. Historically, daytime running lights evolved in Sweden, from low levels of ambient light levels in winter and the national switch from driving on the left (as in the UK, Australia, New Zealand etc) to driving on the right to align with rest of the world. That change happened in 1967, and the first car designed with always-on lights was the 1974 Volvo 200 series. Even so, when the ‘Ride Bright’ campaign in London launched a year later, car driving with lights-on in daytime was almost unheard of. And until recently, vehicles with daytime lights were likely to be motorcycles. Only in February 2011 did an EU regulation came into effect requiring all new cars, vans, truck and buses etc to be equipped with automatic-on day running lights (confusingly also termed ‘DRLs’).
Many of the studies finding positive results from the use of motorcycle DRLs were carried out prior to 2011 when any vehicle with lights-on during daytime was highly likely to be a motorcycle. That situation has now changed. Espie et al (2014) stated:
“The main safety measure in the past has been the use of daytime running lights (DRLs) by motorcycles, which became compulsory in the seventies in many countries. This conspicuity advantage of motorcycles as the only vehicles with DRLs is presently getting lost by the growing use of DRLs by cars as well. In a first study we have shown that car DRLs are competing light patterns that create visual noise and decrease the detectability of motorcycles. In addition to detection errors, the misperception of the approaching motorcycle’s speed and time-to-arrival also contributes to accident occurrence and severity.”
Cavello & Pinto (2012) similarly concluded that car day running lights create ‘visual noise’ interfering with the visual perception of motorcycles:
“Photographs representing complex urban traffic scenes were displayed briefly (250 ms) to 24 participants who had to detect vulnerable road users (motorcyclists, cyclists, pedestrians) appearing at different locations and distances. Car DRLs hampered motorcycle perception compared to conditions where car lights were not on, especially when the motorcycle was at a greater distance from the observer and when it was located in the central part of the visual scene.”
In the TRL review of motorcycle conspicuity carried out in New Zealand, Helman et al (2012) addressed this point:
“Jenness et al. recommended that in light of their findings regarding the possible detrimental effects on motorcyclist safety on urban roads, if DRL for the wider vehicle fleet continues to rise then other measures should be taken to increase motorcyclists conspicuity at the same time, and in such a way that motorcyclists are given a ‘visual signature’ that is not reliant simply on lights that may be confusable with the lights used on the majority of other traffic.”
So what might work? Here are some of the alternative strategies that have been used, trialled or proposed:
- high beam in daytime
- bigger headlights
- pairs of running lights
- low wattage, wide angle running light
- LED running lights
- the ‘triangle of lights’
- lights above the head or on the helmet
- headlight modulators
- live light projection
Some riders – perhaps because it’s been recommended by a few rider action groups – use high beam as a DRL. However, as well as annoying other road users with the dazzle, it’s possible it could act as camouflage against a bright background – when silhouetted again a bright backdrop, the bright beam may match the luminance of the background and rather than acting as an attractant, serves to hide what’s behind the light. This was the principle behind the WW2 active camouflage known as ‘Yehudi lighting’.
As early as 1985, it was being proposed that bigger headlights would improve conspicuity (Donne & Fulton, 1985). Field trials by Donne (1990) found that headlights more than 180 mm (7″) in diameter [ie; larger than the standard 6″ or 7″ round headlights commonly fitted to machines at that time], had more impact compared to smaller headlights.
The same studies also found positive results for pairs of lights. “Pairs of running lamps… were found to improve the conspicuity of a motorcyclist” (Fulton & Fulton, 1985). Donne (1990) also proposed two running lights following field-trials.
An alternative was to fit a light using a low-wattage bulb behind a wide-angle lens which ‘sprayed’ the light beam left and right of the bike’s path, as well as up and down. In other words, it would be pretty much the opposite of a conventional tightly-focused dipped beam. It’s no coincidence that some police bikes mounted a single low-powered light on their fairings for many years. So did AA machines. [I believe this information came from a TRRL study – I’ll add the link should I find it.]
Increasingly, modern machines are coming with factory-fit LED DRLs, and some riders are retrofitting car-style LED lights, but unless they have some specific characteristic which distinguishes them from the LEDs fitted to cars and other vehicles, it seems unlikely they’ll provide any significant benefit.
Having fitted an uprated halogen dipped headlight conversion to my 1978 Honda 400-F and discovered the charging system was barely capable of running low beam all day in London, I came up with Plan B. Realising that the wide angle lens mentioned above was – more or less – a bolt-on 21w car reversing light, I fitted a pair either side of and just below the headlight and ran them with the side light bulb in the main headlight.
It seems I unwittingly created a ‘triangle of lights’, a strategy that has recently been evaluated and is gaining favour with riders. It was one of the conspicuity strategies that was mentioned in the BikeSafe course I attended in May 2018. But here’s a question. By creating an unusual triangular pattern of lights, what is the intent? To draw more attention than a standard motorcycle with just one or two dipped headlights, or to assist in better speed / distance calculations? Paine et al (2005) referred to a previous study:
“Rumar notes that a single headlamp does not provide adequate distance information and he suggests that three lamps, mounted in a triangular pattern, may assist in speed and distance estimation. This observation by Rumar, combined with the recent studies of motorcycle accidents where most motorcycles had headlights illuminated in the daytime, indicates that single low-beam headlights might not be particularly effective as motorcycle DRLs.
But does the ‘triangle of light’ work in the conspicuity role? Pinto et al (2014) found positive results, but in showing subjects “…photographs representing complex urban traffic scenes” for 250ms ( one quarter of a second), their subjects were asked to pick out:
“…vulnerable road users (a motorcyclist, bicyclist, or pedestrian) on color photographs displayed on a large screen. If one was detected, they had to identify it.”
Here’s a problem. Success rates in detecting otherwise hard-to-spot objects soar when the subject is primed by being asked to pick out a specific object within a static scene. The fact that the subjects knew roughly what they were looking for means we should treat these positive results with some caution. By contrast, FEMA’s “European Agenda for Motorcycle Safety” states that:
“In countries already having introduced mandatory daytime running lights for all vehicles, studies of… additional motorcycle light arrangements, such as triangular lights, to maintain conspicuity, show little or no effect.”
Do extra lights actually help “with detection”? We’ve seen that the ‘triangle of light’ lighting strategy adopted by many riders, which places two extra running lights lights lower down either side of the machine, appears to offer strictly limited benefit in the role of helping drivers spot the machine in a cluttered urban environment. Positive results seem to be confined to improving judgement of the approaching motorcycle’s speed and distance, and differentiation at night.
I’d suggest results also depends on the supplementary lights. Believing ‘brighter is better’, many riders usually re-purpose lights which are designed for other roles. Many fit spotlights which – just like the headlight – likely to be too tightly focused. Fog lights are wide-angle but when raised to the level of the driver’s line-of-sight, are once again too bright and create problems with glare. As far as I can see, the trials that gave positive results used supplementary lights with a combination of lower output and wider angle.
The TRL 2012 literature review (Helman et al) provides a broad summation of the benefits of lights:
- lights-on generally seem to be least effective at improving detection in a cluttered environment
- lights-on generally seem to be better at improving detection at distance in an uncluttered environment
- the tri-light configuration seems to have relatively little benefit in a cluttered environment
- the tri-light configuration seems to have some positive benefit in terms of speed / distance calculation in an uncluttered environment
- the tri-light configuration seems to confer a benefit at night over a single standard headlamp
If the tri-light strategy isn’t effective in terms of being seen, then believing the ‘triangle of lights’ to be a conspicuity aid seems to be a misunderstanding of the intended function. The triangle of lights may help drivers avoid turning into too-small gaps ahead of PTWs, but the arrangement does not appear to help those drivers see the bike in the first place.
Other, weirder, lighting patterns have also been mooted. Honda trialled a motorcycle with a light bar set high above the rider’s head some years ago – you’ll notice that the light on the bar has actually vanished into the bright background. In 2007, Tsutsumi and Maruyama from Honda’s R&D department in Japan published a paper rather-confusingly entitled “LONG Lighting System for Enhanced Conspicuity of Motorcycles”. Although there is the term ‘enhancing conspicuity’ in the title, the research really looks at how to improve the driver’s ability to detect the bike’s speed and distance correctly – as I have previously stated, they are different problems.
The researchers looked for a lighting system “specifically to enhance the ability of the driver of an oncoming vehicle to judge distance and speed of a motorcycle”. They proposed that, “in order to emphasize the longitudinal size of the body” they would place lights to either side of the bike, from “a low position on the front fork to a high position on the body” with the “same lamp luminous intensity as conventional motorcycle position lamps”. Note the term position lamps – these are NOT bright spotlights. They placed four extra amber lights (which appear to be derived from standard indicators) on the machine, two at mirror level, two down by the front axle.
This, they argued, “prevents the observer from recognizing the size of the body as being small, and aids the observer in more accurately judging the speed of an oncoming motorcycle”. Their results suggested that both at night and in daylight the LONG lighting system improved the driver’s ability to judge the motorcycle’s distance and speed, equal to their judgement of an approaching car.
Pinto et al (2014) found that adding an extra LED on the rider’s helmet had benefit in a laboratory study. It’s not entirely a new idea in a somewhat different context, as this archive video from 1966 shows:
Helmet-mounted lights have practicality issues. The light needs a power source and whilst modern LEDs don’t need the big batteries (see the video) that an incandescent bulb requires, it’s one more thing to (forget to) charge up. More worrying is the potential for compromising safety. Although a rechargeable battery could be fitted to the helmet, anything added to a safety helmet which is not strictly necessary for the helmet’s primary role is an unattractive option. Minimising the weight of a helmet is particularly important in reducing head injuries in a crash.
Another suggestion has been to fit an electrical controller that creates a ‘pulsing’ dipped beam (rather than an on / off / on flashing light) by using a device called a ‘headlight modulator’. Results of trials seem to indicate that whilst they enhance detection at a distance, there’s no benefit to be found close up, at the distance that the final and critical ‘looked but failed to see’ error would occur. They are also illegal in most of the world.
Even stranger is a system reportedly being developed by Suzuki for live light projection technology. The patents filed show a series of LEDs projects light at the ground to as a rider aid, but also to act as a warning system directed at other road users. My guess is that that warning function at least will never see the light of day. I anticipate it will be superceded by wireless vehicle-to-vehicle communication (V2Vcommunication) transmitting position and speed data to one another before it goes into production.
You’ll remember, we don’t just need to be seen, we need to be recognised – we need a ‘visual signature’ that tells a driver the light belongs to a motorcycle. In trials, it’s often claimed unusual lighting patterns help PTWs stand out. However, I recall a study [for which I am currently searching] that suggested otherwise. When motorcycles were fitted with patterns of LEDs intended to enhance conspicuity, subjects quickly spotted the lights, but then fixated for lengthy periods of time before taking appropriate action, because the lighting arrangement failed to provide them with the visual signature needed to rapidly identify a PTW. In the study, although it took the subjects longer to detect a motorcycle with no lights, when they did spot it, they responded much more rapidly. And motorcycles with single headlights produced the quickest response because they had a positive ‘visual signature’. I realise that without the paper to confirm my memories, this is all rather anecdotal, but it is worth considering that:
- if there is a benefit to a single headlight, it’s that when seen, it’s rapidly recognised as a motorcycle
- if there is a disadvantage to alternative lighting systems it is that they do not offer a reliable ‘visual signature’
Until such time as there might be a standard improved lighting scheme fitted to ALL motorcycles and scooters – and that would take many years, even if legislation were enacted to enforce a standard for new machines – there’s a risk that unusual lighting patterns could create driver confusion, not recognition.
There is a second consideration. Safety organisations calling for compulsory DRLs usually envisage fitment to new machines, but alternative lighting systems needs to be practical. As long ago as 1985, the TRRL realised that it was important to look for “simple and cheap options which are effective” – bearing in mind many PTWs are purchased as economical transport, I believe the potential cost is often overlooked. It’s also likely that some schemes – such as mounting lights low down on forks and on the ends of mirrors – would be vulnerable to damage and expensive to replace. For the majority of owners, retro-fitting the more complex lighting arrangements (such as the LONG lighting system) to existing machines is unlikely to be appealing. And remarkably, the safety aspect of helmet-mounted lights was not a consideration in the study that recommended it.
So let’s try to sum up what we’ve discovered.
As we knew already, a standard headlight on low beam has strictly limited effectiveness as a DRL but now we have a better understanding of the compromises the role of night-time light and DRL places on the dipped headlight and how the environment in which DRLs are used has changed since the early research.
We’ve looked at a wide range of alternatives including a low-wattage, wide-angle DRL. We’ve found that the ‘triangle of light’ improves judgement of speed and distance but appears to have limited effect in aiding detection in traffic.
In a recent paper “Improving car drivers’ perception of motorcycles: innovative headlight design as a short-term solution to mitigate accidents”, Espie et al (2014 ) l, conclude that the ultimate solution to car – bike collisions is not to work with the human ability to detect other vehicles, but to institute vehicle-to-vehicle communications systems. The authors see any conspicuity strategies as an interim measure.
My conclusion is that from a practical point-of-view, DRLs of any sort – like hi-vis clothing – are not a ‘fit and forget’ measure. We need to assume that we are NOT seen rather than anticipate that DRLS will have any significant impact on our conspicuity, and be ready to take pro-active action. As Owen Morris, a regular contributor on my Facebook page put it:
“We need to act smarter, not appear brighter”
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Monday 1 May – minor edit for clarity
Monday 14 January 2019 – added BBC archive video of helmet light Friday 21 December – added Helman et al (2012) passage about DRLs Friday 14 December – added source for improved headlight design focusing more light downward – Lloyd J (2018)
Cavallo, V. & Pinto, M (2012) “Are car daytime running lights detrimental to motorcycle conspicuity?” Accident Analysis & Prevention Volume 49, November 2012, Pages 78-85
de Craen, S., Doumen, M., Bos, N. & van Norden, Y. (2011) “The roles of motorcyclists and car drivers in conspicuity-related motorcycle crashes”, Stichting Wetenschappelijk Onderzoek Verkeersveiligheid SWOV, Leiden, Netherlands
Donne, G., L., Fulton, E., J. (1985) “The evaluation of aids to the daytime conspicuity of motorcycles” Transport and Road Research Laboratory report
FEMA (2004), “European Agenda for Motorcycle Safety”
Helman, S., Weare, A., Palmer, M. and Fernandez-Medina, K.(2012) “Literature review of interventions to improve the conspicuity of motorcyclists and help avoid ‘looked but failed to see’ accidents”, Transportation Research Laboratory, Project report No. PPR638
Hole, G., J & Tyrrell, L. (1995) “The influence of perceptual ‘set’ on the detection of motorcyclists using daytime headlights” Journal of Ergonomics Volume 38, 1995 – Issue 7 https://doi.org/10.1080/00140139508925191
Lloyd, J. (2008) “Understanding retroreflectivity – A brief history of retroreflective sign facesheet materials” www.rema.org.uk/pub/pdf/history-retroreflective-materials.pdf
Retrieved 14 December 2018
Paine, M., Paine, D., Haley, J. & Cockfield, S. (2005) “Daytime running lights for motorcycles”, Transport Accident Commission of Victoria Australia
Pintoa, Cavalloa and Saint-Pierre (2014) “Influence of front light configuration on the visual conspicuity of motorcycles”. Accident Analysis and Prevention 62
Espie, S., Cavallo, V., Ranchet, M., Pinto, M., Vienne, F. et al. (2014) “Improving car drivers’ perception of motorcycles: innovative headlight design as a short-term solution to mitigate accidents” 10th International Motorcycle Conference, Sep 2014, COLOGNE, Germany. 11p.
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