What is the point of flashing lights?

Bustacapp

I've never understood why cycling lights flash. I always think they are far less visible than a nice, bright and solid 'always on' light. I saw a guy battling through the bleak morning darkness this morning with a constant light on and it was so much easier to spot from the cosy warmth of my car.

Is it to save battery power or what?

adr82

I find the opposite is true. They stand out from most of the other lights you will see which are all solid - traffic lights, vehicle lights, streetlights, building lights, etc. If they weren't highly visible then emergency vehicles wouldn't use them! Anyway every light I've ever bought (even a tiny cheap one) has had both solid and flashing modes, so it's not like you can't pick and choose if you want.

TakeTurns

Constant light should be used to lighten up the road ahead for pot holes etc. A flashing light is mainly used to gain the attention of others as it is more alerting. Due to cyclists being vulnerable road users.

Bustacapp

adr82 wrote:

I find the opposite is true. They stand out from most of the other lights you will see which are all solid - traffic lights, vehicle lights, streetlights, building lights, etc.

I don't see how the light being in 50% darkness can help visibility. And I don't understand with the light not being distinguishable from other solid lights, as long as you see a light then you know there is an obstacle to avoid!!

adr82 wrote:

If they weren't highly visible then emergency vehicles wouldn't use them!

If you could get a bike light that can perfrom like this then I agree:

Pross

TakeTurns wrote:

Constant light should be used to lighten up the road ahead for pot holes etc. A flashing light is mainly used to gain the attention of others as it is more alerting. Due to cyclists being vulnerable road users.

This. Anything moving catches the attention more. I have 3 rear lights one on constant and the other two on different flash modes. Front I have a light to light unlit country lanes and another on flash for catching attention. It does also help that flash mode extends battery life but that's not the main reason. Reflective bands on the ankles are also very good at catching a driver's attention.

richard_farrant

I thought the Highway code says that you have to have a solid light on the rear?

king_jeffers

I normally have a solid on the rear ( :oops: ) + a flasher... Usually a just a cheapo knog light.

Pross

Richard Farrant wrote:

I thought the Highway code says that you have to have a solid light on the rear?

Nope

The Highway Code wrote:

60
At night your cycle MUST have white front and red rear lights lit. It MUST also be fitted with a red rear reflector (and amber pedal reflectors, if manufactured after 1/10/85). White front reflectors and spoke reflectors will also help you to be seen. Flashing lights are permitted but it is recommended that cyclists who are riding in areas without street lighting use a steady front lamp.

Of those it is the reflectors (particularly the pedal reflectors) that most cyclists, including me, don't adhere to. The pedals are a bit of an issue with clipless but I'm hoping to get some orange reflective tape that I can stick onto them and the back of my shoes.

CiB

Bustacapp wrote:

I don't see how the light being in 50% darkness can help visibility. And I don't understand with the light not being distinguishable from other solid lights, as long as you see a light then you know there is an obstacle to avoid!!

But you know that's wrong. Put two lights one flashing and one solid in a busy visual environment and the flashing one will attract your attention. It's not the quantity of the light, it's the intermittent nature that makes it more visible. Being off for lord knows how many hundredths of a second doesn't make it not a light.

And like others have said, you use both anyway. Flashing so that the numpty half-asleep drivers might spot you, and fixed because it's what the HC requires and is also visible. I have three at each end, 2 solid 1 flashing. Sometimes the other way round on the back.

adr82

Bustacapp wrote:

I don't see how the light being in 50% darkness can help visibility. And I don't understand with the light not being distinguishable from other solid lights, as long as you see a light then you know there is an obstacle to avoid!!

It's not like it's dark for 5 seconds! The lights I use flash several times a second, you're not going to miss it even if you just do a quick glance in its direction.

CiB wrote:

Bustacapp wrote:

I don't see how the light being in 50% darkness can help visibility. And I don't understand with the light not being distinguishable from other solid lights, as long as you see a light then you know there is an obstacle to avoid!!

But you know that's wrong. Put two lights one flashing and one solid in a busy visual environment and the flashing one will attract your attention. It's not the quantity of the light, it's the intermittent nature that makes it more visible. Being off for lord knows how many hundredths of a second doesn't make it not a light.

Exactly. Human eyesight is drawn to change/movement in the surrounding environment, so you'd expect that a flashing light would be noticed faster than a solid one. Don't know if anyone has actually done any research to verify this though. In my own experience I find it far easier to pick out a single relatively dim flashing light on a busy street compared to a solid light in a similar situation.

Mr Will

As others have said - sudden changes instinctively draw your eye making a flashing light easier to notice, if not necessarily easier to see.

Flashing is particularly helpful in the presence of lots of other lights - a solid bike light that would be bright and easy to spot on a country lane will blend in dangerously on a wet city street surrounded by traffic; that's where a flashing light comes in to it's own.

Pross

When I use my main front light on flash in an urban environment all the reflective street lights start flashing and you see drivers (and pedestrians) looking about to work out where it is coming from which to me shows it is doing its job.

bompington

Plenty of quality flashing and fixed lights to choose from here

bluedoggy

I use a Exposure Maxx D on Flash slightly dipped so not to blind. I definatley get noticed.....

Peddle Up!

Mr Will wrote:

Flashing is particularly helpful in the presence of lots of other lights - a solid bike light that would be bright and easy to spot on a country lane will blend in dangerously on a wet city street surrounded by traffic; that's where a flashing light comes in to it's own.

The best argument.

Wrath Rob

Solid light to see.
Flashing light to be seen.

simon_masterson

adr82 wrote:

I find the opposite is true. They stand out from most of the other lights you will see which are all solid - traffic lights, vehicle lights, streetlights, building lights, etc. If they weren't highly visible then emergency vehicles wouldn't use them! Anyway every light I've ever bought (even a tiny cheap one) has had both solid and flashing modes, so it's not like you can't pick and choose if you want.

This!

My first LED light had flashing modes, but that was before they were technically legal. I always use a flashing mode on my rear light for the reason given above; never on my front light however. I understand why some people do but I use it to see with!

The one and only gripe I have ever had with flashing modes is that they usually have non-mechanical switches. That first light I had - best part of a decade ago I would think; it broke about this time last year - was very cheap and suffered from the old problem of battery movement. If the battery shifted despite whatever I'd put in there to attempt to stop it, the light would go out (which resulted in one or two near misses!); my trusty Cateye HL500 (which still works but is in retirement!) having a mechanical switch would just switch back on with a good whack!

CubeMark

Why do car indicators flash? Same reason. To be seen.

jameses

Wrath Rob wrote:

Solid light to see.
Flashing light to be seen.

This

geebus

I can't find the image I was looking for, but it was a 'better' (bike more hidden) idea along the lines of this:

(In the picture I was thinking of the bike in front was lined up with the headlights behind fairly well from the viewpoint of the picture and at a glance you would expect there to be two vehicles there with a more vulnerable one in front.)

With daylight running lights motorcycles and of course pedal cycles can easily be hidden in a haze of other single-point light sources out there.
Even worse at night.
A flashing light makes it significantly more noticeable as these aren't used on motor-vehicles apart from for turn signals.

PlymouthSam

I have always said id rather put my light into "disco" mode and annoy people so they see me then normal mode and blend in !

rolf_f

Generally always best two have two entirely separate units on front and back. On the front, I'll either usually have one flashing or both on fixed if I'm on unlit roads. The back ones are generally both flashing which reduces the likelihood of the batteries running out on me. Two Smart half or one watt types are plenty solid or flashing but they look far more noticeable to me in flashing mode.

That said, choice of light is probably more significant than mode - most of the riders I see using Cateyes are effectively almost in stealth mode until you are almost right behind them. I wonder whether some people have ever actually checked how bright their rear lights are.

mobilekat

The best way to be seen is to combine lights and hi-viz.

I do lots of driving and the cyclists I see the earliest are the ones with hi-viz, flashing lights and a steady light too.
I have seen a few people out with a rear flashing light mounted on their helmet and these are the most obvious from behind as it raises it up, and prevents clothing etc masking it.

The Hi-viz also helps, as it gives more movement, and being an irregular movement this is picked up quicker by the eye. They did a study about horse riders wearing hi-viz and no lights and it was found hi-viz get you seen on average 3 seconds sooner!
Having been out both on the bike today, and out driving I do wish more people would think about being seen, as with low early winter/autumn sunlight it can be a real nightmare to see people!

tiredofwhiners

You all missed the point.

The batteries last longer when in flash mode than in steady and it gives you more chance to remember that your batteries need changing

rolf_f

tiredofwhiners wrote:

You all missed the point.

The batteries last longer when in flash mode than in steady and it gives you more chance to remember that your batteries need changing

Rolf F wrote:

The back ones are generally both flashing which reduces the likelihood of the batteries running out on me.

Yep - I missed the point

Pross

Rolf F wrote:

tiredofwhiners wrote:

You all missed the point.

The batteries last longer when in flash mode than in steady and it gives you more chance to remember that your batteries need changing

Rolf F wrote:

The back ones are generally both flashing which reduces the likelihood of the batteries running out on me.

Yep - I missed the point

Pross wrote:

This. Anything moving catches the attention more. I have 3 rear lights one on constant and the other two on different flash modes. Front I have a light to light unlit country lanes and another on flash for catching attention. It does also help that flash mode extends battery life but that's not the main reason. Reflective bands on the ankles are also very good at catching a driver's attention.

Me too!

the_cyclist_of_catan

It's because humans have been hunters for most of our evolution, and our visual system is attuned to spotting movement - or other sudden changes of state. There has been plenty of research done on this. Note that flashing lights can make judging distances trickier, which might be one of the benefits of a combination of rear lights, one flashing, one steady.

saprkzz

JamesEs wrote:

Wrath Rob wrote:

Solid light to see.
Flashing light to be seen.

This

+2

I use exposure maxxd on solid with Diablo on flash mode for the front.

On rear I use Exposure flare on solid on seatpost, and use one of these bad boys flashing on my jersey, these are blooming amazing!



Can be seen from the side and give loads of light to draw attention without dazzeling car drivers and other cyclists drafting like some rear lights do. The battery lasts for ages. They come with straps so can be put down the seat post as well.

saprkzz

Good demo of the fibre flare here:
(the bike one is shorther than the motor cycle like being demonstrated on the helmet but near the end of vid he shows the one i have.

http://www.youtube.com/watch?v=VKGYsiihSkM

h34e0f

Flashing lights save battery life, nothing else. They are incredibly hard to see from both the point of view of motorists, pedestrians and cyclists. If you only glance before pulling out (and most people do) there is a 50/50 chance that you will not see the light. I have walked out in front of cyclists before simply because I did not notice the flashing light as it was OFF at the exact point I looked.

Also, as a driver, you have absolutely no perception of distance or speed of a flashing light.

saprkzz

h34e0f wrote:

Flashing lights save battery life, nothing else. They are incredibly hard to see from both the point of view of motorists, pedestrians and cyclists. If you only glance before pulling out (and most people do) there is a 50/50 chance that you will not see the light. I have walked out in front of cyclists before simply because I did not notice the flashing light as it was OFF at the exact point I looked.

Also, as a driver, you have absolutely no perception of distance or speed of a flashing light.

The high quality lights (like exposure) have the main light stay constant and flash at the same time, in town and junctions I would never ride without them on flash, country roads in a straight line then i keep them without flash.

It has saved me from hitting the deck many times.