Flashing rear light enhances driver perception of cyclist ahead

slideshow bob

Interesting research article, even if the experiments were somewhat simplified.

https://www.sciencedirect.com/science/article/pii/S0001457523004657

In conclusion, flashing rear cycle lights, regardless of reactive technology, enhanced drivers’ perception of a cyclist ahead, notably in terms of their judgements of distance to that cyclist.

tomasrojo

I seem to remember that it was common enough to claim that drivers had trouble perceiving how far away a cyclist was based on just a flashing light (which I think led some people to use one fixed light and one flashing), and that flashing lights were supposed to have an effect of causing some drivers to fixate and bend their trajectory towards the cyclist (can't remember whether there were studies this was based on).

I would definitely believe that a flashing red light is emblematic of a cyclist for just about everyone. I'm not sure drivers behave any better on that basis though. Based on my experience of "dressing like a cyclist" versus "dressing like a normal person", it might be possible that the behaviour of drivers gets worse when they realize who's up ahead.

I like a medium-intensity fixed light, but with a big face, or two lights of medium intensity mounted contiguously, for similar effect. Not sure it works as well as high-intensity or flashing lights, but it's very visible, without sort of pleading to be seen, which I think can set off people who have been listening to Newstalk.

tomasrojo

It doesn't look an amazing difference in how drivers perceive distance but I might be misunderstanding.

beggars_bush

Flashy red light makes you stand out from other traffic though. I don't want to look like a car with dodgy rear lights from behind

Those flashing red strobe lights can be seen from over 1km away, apparently

CramCycle

My reading of the paper is that technically, when pre warned, motorists will react to static lights quicker but are slightly better at depth perception with flashing lights. In reality, it's hard to take anything from it the differences are so minute it can't tell you anything other than if drivers are focused, they will see someone at roughly the same time if paying attention (and at the distance and lighting used for the test).

tomasrojo

https://www.boards.ie/discussion/comment/122685377#Comment_122685377

Reminds me of that Australian hi-viz study, where the participants turned out to be pretty good at seeing the cyclists with no lights and no hi-viz, and the people doing the study assumed the participants were so keen to perform well in the study they were far more vigilant than was usual in the scenario they were trying to recreate.

fat bloke

Garmin rear light is amazing in terms of visibility from way off. I always use it in flashing mode, saves the battery too.

SchrodingersCat

https://www.boards.ie/discussion/comment/122685231#Comment_122685231

flashing lights were supposed to have an effect of causing some drivers to fixate and bend their trajectory towards the cyclist (can't remember whether there were studies this was based on).

I can’t comment on particular with road drivers, but this phenomena is called “target fixation ”. It has been known since WWII where fighter bomber pilots would end up flying into targets instead of bombing them.

It is a lesson why drivers should look at where they want to go, not stare at what they don’t want to hit.

I’ve noticed it while cycling in painted cycle lanes. Cars that are going past will sometimes drift in towards me over the line before correcting their trajectory.

I can vouch on what you say about drivers treating you differently if you are “dressed like a normal person” vs “dressed like a cyclist”. Drivers seem to be more forgiving and respectful if you are dressed more like them than in the full gear. There is something psychological going on there.

magicbastarder

I was always a practitioner of the 'one flashing, one steady' option when I was commuting. Not that I was a true believer of the theory, but I was hedging my bets. Plus, to have two lights for redundancy.

But one context I think flashing lights are probably good in, is rain. A tired or distracted motorist looking in a rain spattered wing mirror might not correctly interpret a steady light reflecting off multiple droplets, where a flashing light will be a more obvious signal of a cyclist.

Nigzcurran

I drive a van for a living on all sorts of roads and for me personally I can see a flashing red light far more easier than a static one, having both is definitely the best option especially now coming into the dark wet mornings. Some of the white front lights can be a bit blinding, could be they are pointing upwards too much but id still prefer that to a cyclist who has no lights

standardg60

I would have thought it's a no brainer, flashing lights are simply more attracting/distracting to the human eye and are noticed sooner. A flashing light in a wing mirror will draw your attention before you even look at it.

It's no different to an indicator, if indicators didn't flash they would be far less noticeable. Same for emergency vehicles.

sudocremegg

No brainer really, coupled with hi visibility reflective clothing you have a better chance of being perceived.

magicbastarder

FWIW, and this only happened once; I was in the clontarf cycle path at the final section near east point, and briefly thought I could see a car heading straight for me, albeit some distance away. Probably took less that a second to cop that it was a cyclist with two steady white lights, but very briefly my brain interpreted them as car headlights. That fed into my decision to go one steady, one flashing.

rflynnr

I used to use two lights - one solid, one flashing - based on the logic outlined above. Last year, I bought a Magicshine SeeMe 300 which does both. A permanent red and a pulsing one (with two different LEDS). Just a bit handier then two (and came with a great under-saddle fitting option along with the standard seat post mount).

Johnners1878

https://www.boards.ie/discussion/comment/122686741#Comment_122686741

That looks impressive & good value too. Is it available locally or just online?

tomasrojo

Thing is, whatever about the fixation theory and judgment of distance theory, I actually think there's a balance between being visible and drawing too much attention to yourself. The worst incidents I've had on the road haven't been from people failing to see me, and in any case I've gotten very good at knowing when someone hasn't seen me (usually because they're not thinking two moves ahead in a manoeuvre) and dealing with it. The worst have been people deciding to punish me or teach me a lesson based on some demented Newstalk logic or just standard bully personalities. So going through estates with bored people hanging around on corners I like to turn down the conspicuity considerably. And once I'm very adequately visible on the main road I don't want to get to the point of demanding or pleading to be seen, because that seems to bring the worst out in some people.

tomasrojo

I suppose part of my problem with a lot of road safety thought is that it's based on the model of rational drivers who are doing their best, but there is a not imperceptible minority that is nothing like that, and though it's impossible to know the extent, these awful people, through punishment passes and prank passes that go wrong, make up part of the tragic "they came out of nowhere" stories that gardaí hear every year.

tomasrojo

I should say that recently on two separate occasions a pedestrian and a driver stopped me to tell me how good my lights were, so I'm pretty sure they're adequate.

tomasrojo

My basic approach (not based on anything more scientific than anyone else's) is that lower-intensity lights should be set to flash, and higher- to steady; though maybe in dense fog it's good to go for broke.

CramCycle

Just not a fan of flashing lights on experience with target fixation (they used to be banned on Audaxes) and my lights are bright enough in rural scenarios that people not paying attention slow down as if I'm a slow moving motorbike or car with only one front light. Like Tomasrojo, I have gotten compliments for my lights. I also think that my lights are bright enough that if flashing would be a decent distraction.

If research comes out showing me conclusively wrong, I'll adapt, I til then it's solid lights for me.

magicbastarder

well, the purpose of flashing and steady can be separated into two - flashing is for others to see you. steady is for others to see you, and for you to see. so i'd agree that a flashing light has done its job once it's noticed.

a clanger

https://www.boards.ie/discussion/comment/122685729#Comment_122685729

I agree and coupled with the radar its the best bit of kit I ever bought. I get a visual and aural warning of approaching traffic reminding me to keep in and pay attention.

rflynnr

https://www.boards.ie/discussion/comment/122686810#Comment_122686810

I bought it direct from Magicshine for US$60. Shipping was free. Apparently it has some class of brake light setting but I've never engaged it.

rflynnr

Incidentally I also bought one of their Alty 1500 front lights with which I'm also very happy. The initial appeal of both was the mounts to the honest. I'd gotten fed up of fiddling with rubberstraps in the dark before the commute home. I used to be kind of sniffy about Magicshine because they were Chinese. Then I reflected that a) this was just a tad racist and b) because VIRTUALLY EVERY OTHER LIGHT I'D EVER BOUGHT WAS ALMOST CERTAINLY MADE IN CHINA.

Seth Brundle

Out of curiosity, the German StVZO (road traffic laws) prohibit flashing lights on bikes (but apparently it goes unenforced). Does anyone know the logic behind this prohibition?

standardg60

https://www.boards.ie/discussion/comment/122688185#Comment_122688185

Germany's StVZO bike light regulations dictate that flashing bike lights are not permitted on either the front or rear of a bike. The regulations state this is because flashing patterns can be distracting to other road users. Flashing bikes are also outlawed in the Netherlands and Austria.5 Oct 2023

Funny, I thought that was the entire point.

Wishbone Ash

https://www.boards.ie/discussion/comment/122688185#Comment_122688185

It may go unenforced but they still aren't available on German online sites.

Flashing lights on a bike were illegal here until about 10/12 years ago IIRC.

khamilton

I turned my lights to solid rather than flashing when cyclepacking around central Europe this summer, and can't recall seeing ANY flashing bike lights in the 4 countries I visited.

beggars_bush

The flashing setting lasts much longer in terms of battery so if I'm out for 3 hours+ it'll be on flashing

secman

Yep on flashing, recently bought the Megane radar rear light and only use it on Flashing mode. The great thing about them is, as soon as they pick up a car they Flash more .

John_Rambo

I'm a bit obsessed with lights on the bike. When the flashing lights came out first I was all over them, got a set in the Netherlands. I'd a few comments from drivers in traffic about the legality of them and how they blinded drivers. I also had a trailer for the kids (15 years ago) and I was accused of child abuse and child endangerment from drivers!

Attitudes are slowly changing.

Paddigol

https://www.boards.ie/discussion/comment/122686977#Comment_122686977

I'm inclined the same way… My set up if I'm commuting solo is; good light set to solid beam on seat post, one cheaper flashing on drivetrain seatstay and one back up cheap & chearful light backup on non-drivetrain side. Logic being - solid beam on good light is for visibility from distance, low flash setting on seatstay is for reminder/ warning to drivers closer in distance. But if I had to have one, it would be solid beam.

Am I right in saying that flash setting lights are banned in Germany? I presume there's a scientific/ safety reason behind it?

I've said it loads of times but I wish there was a good universal standard/ guide to lights here. The options are just crazy, big brand and expensive doesn't necessarily equal quality. Unless you're 'sciency' you just get completely bamboozled by the options out there.

I don't obsess over the lights in my car - the lights are the lights, I know they'll do the job, and all I need to do is replace the buld and get them re-aligned every now and then. I'd love if it was that simple with bikes. Would deflate a lot of the hi-viz guff too.

magicbastarder

IIRC it used to be the case in ireland that flashing lights were banned on all vehicles except emergency services vehicles. they changed the law here to allow it on bikes.

so if they're banned in germany, it may be a similar situation, in that they didn't set out to specifically ban them on bikes; if that is the case, there would have been no scientific/safety investigation first.

Paddigol

https://www.boards.ie/discussion/comment/122692593#Comment_122692593

Here's a bit of info I found… a bit more that just the flashing element of lights, seems to include the type of beam too.

StVZO bike lights: everything you need to know | BikeRadar

Mefistofelino

https://www.boards.ie/discussion/comment/122692593#Comment_122692593

I think it was the case that flashing lights were not permitted as the only source of (rear) illumination. Amber flashing lights have been used as supplementary warning on vehicles for decades.

07Lapierre

I set my rear light to flashing day or night. I set my front like to flashing when in daylight and static when it’s dark.

I’ve never understood the two rear lights (1 set to flashing and 1 static) by all means carry a backup set of lights , but if a driver is looking they will see a red flashing light…if they are not looking they won’t see 20 lights, ( if they are flashing or static)

Paddigol

https://www.boards.ie/discussion/comment/122693718#Comment_122693718

In urban traffic I think a different setting does provide an additional ability to catch the eye of an inattentive driver in a sea of continuous solid beam red lights. Just my personal instinct… a bit of the "what's the harm" logic… A bit like the extra brake lights at the top of rear windows on cars now. Maybe they'll see it that 1/1,000 time that their brain doesn't immediately register the solid beam/ bumper brake lights?

It's not something I'm hung up on, but the fear of a dead battery/ faulty rear light does spook me out on solo commutes from town out the N11 to the sticks.

tomasrojo

https://www.boards.ie/discussion/comment/122692963#Comment_122692963

Yeah, the dynamo front light on the family bakfiets is StVZO-compliant, and so is the Cateye front light that I use on the other two bikes I use. It's a nicely shaped beam with a top cut-off, so you can mount the light horizontally without dazzling anyone and so it doesn't waste energy illuminating the tree tops, as described by BikeRadar.

I'll probably keep getting StVZO-compliant front lights.

tomasrojo

Yes, I think it was just that the 1963 legislation notion of "lit" implicitly didn't include the notion of turning on and off. They updated the law in 2009 to say

In this article, ‘lit’ means the emission of a continuous light or a light that flashes not less than 60 times in each minute.

EDIT: Now I check it, this part under the lighting regulations needed to be changed too to allow flashing lights:

 No lamp (other than direction indicators) fitted to a vehicle shall show or be constructed or adapted so as to be capable of showing a flashing light unless such light is invisible to persons outside the vehicle.

So I assume it actually wasn't technically allowed to have flashing lights until 2009, even as auxiliary lights.

fiacha

99% of my riding is in daylight now, but I still have flashing (strobing-ish) lights front and rear. I find the irregular pattern stands out more (to my eyes!) than a standard on/off flash. They are not overly bright, but I still angle them down to avoid dazzling people. Some of the bike lights out there now are way too bright, even in daylight. I find them distracting.

I have recently noticed a few bikes with long orange reflective stickers on the seat stays. With a flashing light above them on the seatpost, they stood out very well. To me they looked just as effective as a solid light.

I know that hi-viz is a controversial subject here, but I've always thought that passive reflective ankle straps / cuffs are a really good addition. Any time I've seen someone using them, the movement immediately screams "cyclist".

youtheman

Flashing rear lights are great during daylight hours. Not many clubs cycle in groups at night, but if you do, then flashing rear lights will drive you bonkers !.

65535

I'd prefer if the firstly just had lights of any kind which a lot do not and dress in black, and further would prefer if it did not flash.

"Photosensitive epilepsy is when seizures are triggered by flashing lights or contrasting light and dark patterns. Photosensitive epilepsy is not common but it may be diagnosed when you have an EEG test. Flashing or patterned effects can make people with or without epilepsy feel disorientated, uncomfortable or unwell."

cletus

https://www.boards.ie/discussion/comment/122694172#Comment_122694172

People with photosensitive epilepsy are affected by lights that have different flash or flicker rates from as low as 3 to as high as 60 per second. Lights that flash or flicker between 16 and 25 times a second are the most likely to trigger seizures.

Some lights, such as bicycle lights (red and white), are covered by UK law, which says that these lights must not flash at less than one or more than 4 flashes a second. Provided the lights comply with the law, they are unlikely to cause a problem.

From epilepsy.org

https://www.epilepsy.org.uk/info/seizure-triggers/photosensitive-epilepsy#:~:text=Lights%20that%20flash%20or%20flicker,than%204%20flashes%20a%20second.

I'm assuming the lights that people use in the UK are similar or the same as lights that people use here, so it would not seem to be an issue

ARX

I did the Dunwich Dynamo once. Out in rural Essex where there was no street lighting (or moonlight) and people in front of me had strobing rear lights on, it was a pain - I ended up having to pass a lot of people because of their lights.

tomasrojo

https://www.boards.ie/discussion/comment/122694135#Comment_122694135

Funnily enough, one of the takeaway points of the Australian hi-viz study I mentioned at the top was that reflective ankle material was more effective than material on the torso.

Paddigol

Yeah, to echo what a couple of posters above have mentioned… flashing rear lights are a real issue on group spins. Even on commutes in urban areas I'll have my flash on the lowest setting. I do find them migraine-inducing on the high setting. There really isn't a need for them at that intensity IMO. While the powerful front lights are superb on dark nights on quiet, unlit rural roads, I've no interest in blinding oncoming drivers/ cyclists/ walkers either. If I do have them on, I'll dip them to low setting when I can see someone approaching. They do provide excellent full-road visibility though

What most of these posts come back to is the lack of properly researched guidelines for all types of cyclists, and accepted, science-based standards. Just go onto any cycling website (not even talking Amazon here) and you'll be bamboozled by the options.

I'm half tempted by the Garmin rear light/ camera option, but not sure how good the actual light is, which would be the main priority. Considering how much money is spent on cycling globally I'm surprised at the lack of options for this kind of set up.

magicbastarder

https://www.boards.ie/discussion/comment/122694213#Comment_122694213

I'm curious as to whether someone whose epilepsy would be triggered by a cyclist's light would also be triggered by an emergency services flashing light or highway maintenance vehicle, etc.?

Jimbo789

they are illegal in Germany

cletus

https://www.boards.ie/discussion/comment/122694494#Comment_122694494

I'd say they are both equally likely to trigger it (or equally unlikely).

fiacha

https://www.boards.ie/discussion/comment/122694335#Comment_122694335

I'm slow and solo, so there's rarely anyone stuck behind me for long :D

Is it also an issue during daytime or just low light / night ?

standardg60

https://www.boards.ie/discussion/comment/122694162#Comment_122694162

You've just revealed how to get the perennial drafters to take a turn at the front!