SOBS October 21 Could a new motorcycle lighting design ‘save lives’?

That’s the claim being put forward by press reports of a new study published in the journal Transportation Research Part F: Traffic Psychology and Behaviour earlier this month. The press release from Rice University’s News and Media Relations department was headlined:

“New motorcycle lighting design could save lives… Alternative to one-headlight setup helps other motorists see bikes almost a second sooner.”

Not surprisingly, it’s already been republished in several locations where motorcyclists are likely to read it.

The press release refers to a new research paper, entitled ‘Effect of Motorcycle Lighting Configurations on Drivers’ Perceptions of Closing’ and authored by Bradley W. Weaver and Patricia R. DeLucia from Rice University, Houston, in Texas is based on Weaver’s PhD dissertation.

The study looked at motorcycles at night. Weaver said in a press release:

“Because motorcycles are smaller than many other vehicles, it is more difficult for other drivers to accurately judge their motion on the roadway. It is particularly difficult at night when a motorcycle has only a single headlight because other drivers can’t see the motorcycle’s full height or width.”

The aim of the study was: “to better understand how drivers perceive an approaching set of motorcycle headlights during nighttime driving and to determine whether alternative motorcycle headlight configurations improve drivers’ perceptual judgments of closing for an oncoming motorcycle”.

In other words, the scenario they were investigating was the one where a vehicle is planning to turn across the path of one coming the other way, rather than the classic ‘SMIDSY’ collision where a vehicle pulls out from a side road.

And to do this, they set up a simulator study in which a ‘driver’ saw approaching lights in various configurations of lights including a standard car light configuration, plus a variety of arrangements of lights representing motorcycles. The participants – all drivers, and most with no experience of riding motorcycles – had to press a key on the keyboard when they detected that the light was actually moving towards them.

Illustration from ‘Effect of motorcycle lighting configurations on drivers’ perceptions of closing during nighttime driving’
Bradley W.Weaver, Patricia R.DeLucia
Transportation Research Part F: Traffic Psychology and Behaviour Volume 90, October 2022, Pages 333-346

I managed to get hold of the PDF of the paper, and I’ve now had a chance to read it.

There are some interesting conclusions.

Firstly, the standard car headlight configuration was most rapidly detected as moving towards the participant. None of the motorcycle lighting configurations were detected as moving as rapidly.

Secondly, drivers find it easier to detect this ‘looming’ movement when a single motorcycle headlight is ‘big’ rather than ‘small’. As far as I remember, this is consistent with a study done here in the UK back in the 1960s.

Thirdly, they also looked at the popular ‘tri-light’ configuration where the single headlight is supplemented with two additional lights. I’ve previously reported studies have suggested positive benefits for the tri-light arrangement at night, and their results also suggest this light configuration that helps accentuate both a motorcycle’s height and width is superior to a single headlight when it comes to detecting movement towards a driver.

Four, they also looked at ‘fully accentuated’ lighting systems that were either:

:: horizontal – a flat row of lights going right across the front of the machine
:: vertical – a row of lights from the bottom of the bike to the top of the rider’s helmet
:: combined – both horizontal and vertical lights

They compared these arrangements against a standard single headlight, a motorcycle with a tri-headlight configuration, and a car’s headlights.

Their results indicated that the headlight configuration that accentuated BOTH a motorcycle’s height and width, or the configuration that accentuated ONLY the motorcycle’s HEIGHT were better than the single headlight or the motorcycle with a tri-headlight configuration.

Of the two, the vertical light arrangement was detected as moving toward the observer sooner.

And so the authors concluded:

“…the fully accentuated vertical motorcycle headlight configuration may be better in terms of practicality because it requires fewer headlights and therefore costs less.”

And they also pointed out that “…motorcyclists would need to wear a helmet-mounted headlight” admitting that it wasn’t a “very common practice” and that “buy-in from motorcyclists would be needed”.

The paper also flagged up a potential problem, although they didn’t identify the real issue. The authors said that “motorcyclists turning their head would change how the oncoming motorcycle appears”, but that’s not actually the problem.

Although the lights in the diagram of the experimental configuration are smaller, there’s no information on BRIGHTNESS – or if there is, I missed it.

If these additional lights actually produce as much light output as the bike’s standard headlight from a smaller lens – as do many of the auxiliary lights currently used by motorcyclists – then a rider with a helmet mounted light turning his or her head to look directly AT a vehicle will actually dazzle the driver. We have low-beam lights for a reason.

I’ve had precisely this problem with cyclists, using powerful helmet-mounted lights. One blinded me completely in the middle of a left-hand bend on a narrow road – I could neither see the cyclist, nor the hedge on the inside of the bend. This is not a trivial problem, and in my opinion precludes the use of bright lights on the helmet.

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Of course, the biggest question of the lot is how much ‘time’ does the vertical light configuration buy the rider?

The answer is that the study found that other motorists were able to see motorcycles “up to 0.8 seconds sooner”.

“Just under a second might not seem like a lot, but reducing a driver’s response time to a potential collision can make a difference between life and death” said DeLucia.

Well, it depends on how far away the bike is, and whether or not the lighting configuration actually stops drivers initiating a turn.

So let’s put the 0.8 second gain in context. The simulation had the motorcycle travelling at 30 mph. That’s 13.4 metres per second. So the maximum extra distance was just 10.7 metres. And you’ll note that the study said ‘up to’ 0.8 seconds.

The study says “when the scene started, the oncoming motorcycle was 750 to 850 ft (228.60 to 259.08 m) from the participant”, but the important point is where was the bike when the driver actually detected the moving motorcycle?

IF I’ve read the results correctly – and to be honest I’m not entirely sure that I have so I’m happy to be corrected – the ‘bumper to bumper’ distances at the moment the lighting configurations were detected as moving ranged from an average of 209 feet for the car lights configuration, to an average of 185 feet for the single motorcycle headlight configuration.

But remember where the bike first became visible – well over 200 metres away.

If my interpretation is correct, and assuming the worst case scenario where the bike first appeared 750 ft or 228.6 metres away, the bike had moved 56 metres before it was spotted. That means it was detected as moving when over 170 metres away.

To put that in perspective, that’s still well over TWELVE SECONDS from the time the bike would reach the observer’s position. And crucially, the study did NOT look at whether the driver would have actually initiated a turn across the motorcycle’s path. The fact is that at that distance, there’s no threat to the rider anyway – the car would clear the rider’s path with time to spare.

And so I’m not sure what the practical benefit of being seen 0.8 seconds – or eleven metres – sooner actually is.

There are also several practical problems which weren’t considered. As I’ve previously stated when helmet-mounted lights have been proposed, there are the problems of:

:: attaching them to a helmet
:: powering them
:: ensuring that the lights, plus any batteries, do not compromise the primary role of the helmet, which is to protect the head in a crash – you’ll probably remember that the latest ECE helmet standard requires that a helmet be tested with options like cameras and radios already attached

Finally, it’s worth pointing out that this was a simulator study. More importantly, the description of the method says “participants downloaded the needed experimental files” and that participants were required to “measure the width of their screens, which the experimenter would then use to calculate the correct viewing distance”. This implies that the study wasn’t run on standardised equipment in a controlled environment, but run on participants’ own computers and screens in their own home. There seems to have been no test to confirm that the various participants got comparable results with each other. The weakness of the study should be obvious.

My conclusion is that it’s an interesting study, but I’m far from convinced that the proposed vertical lights actually create any significant benefit to the rider, that claims that the ‘design could save lives’ are unproven and exaggerated, and compared with conventional lights, there’s little consideration of the practical issues, including the potential for significant inconvenience to other road users being dazzled by a helmet-mounted light.

If you want to make yourself more visible in night-time traffic I’m still of the belief that different-coloured lights are a sound choice.


Each investigation of a research article like
this one takes hours of my time. I give that time
freely to the SOBS project because I believe it
can make a difference by helping riders achieve
a better understanding of the SMIDSY collision.

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