Flashing bike lights

[simonineaston]

My evening leisure run goes along some unlit lanes, and I often meet riders doing the same, either in groups or singly, so I get a lot of opportunity to review the efficacy of their lights... it seems to me that after dark, flashing lights are hard to pin-point in terms of distance. A fellow who passed me the other day, with 2, maybe 3, bright back lights, all set to flash mode, disappeared into the distance (I'm used to that!) and it seemed to me that it was very hard to judge how far away he was at any one time - the flashing seems to make it hard to judge. Has any research been done on the way we see flashing as opposed to steady lights, while in darkness? I don't to be a victim of the same trick-of-the-light?! I have 2 battery LED lamps and at the mo' I set the bright one to steady, and the cheap one to 'sparkle'. Am I right to do so? What's the legal position?

[ukdodger]

My evening leisure run goes along some unlit lanes, and I often meet riders doing the same, either in groups or singly, so I get a lot of opportunity to review the efficacy of their lights... it seems to me that after dark, flashing lights are hard to pin-point in terms of distance. A fellow who passed me the other day, with 2, maybe 3, bright back lights, all set to flash mode, disappeared into the distance (I'm used to that!) and it seemed to me that it was very hard to judge how far away he was at any one time - the flashing seems to make it hard to judge. Has any research been done on the way we see flashing as opposed to steady lights, while in darkness? I don't to be a victim of the same trick-of-the-light?! I have 2 battery LED lamps and at the mo' I set the bright one to steady, and the cheap one to 'sparkle'. Am I right to do so? What's the legal position?

I dont know the legal position but I dont have a problem judging the 'sparkle' option which I take it you mean the running flash from side to side.

[DavidT]

I can't quote any formal research but I believe that the recognised and accepted understanding is as follows;

Flashing lights are better at attracting the attention of the viewer
Fixed lights are better at allowing the viewer to establish the distance

For that reason, many (and obviously including the OP) on here ride with a flashing and fixed light at night. The actual benefits of one or the other or both together will no doubt vary with the riding environment.

Amongst the personal anecdotal evidence I have for this is someone who is professionally involved with accident investigation (although not roads). I guess there is some research out there somewhere.

[simonineaston]

Flashing lights are better at attracting the attention of the viewer
Fixed lights are better at allowing the viewer to establish the distance

That's certainly my impression - I just wondered if was just me or a recognised characteristic of flashing lights.

[Redvee]

Flashing lights are better at attracting the attention of the viewer
Fixed lights are better at allowing the viewer to establish the distance

That is my understanding too. Magicshine on flash with Fybreflare on my pannier bag and Mars 3.0 on my rack both on constant.

[reohn2]

I always have atleast one rear light on "constant" others are on various flashing modes,unless I'm riding in a group in which case I only use the constant one for the sake of others in the group.

[Russcoles]

Bright front lights should never flash in my opinion. The number of people who have front lights powerful enough to dazzle you set to flash is ridiculous. In the dark this is enough to destroy your night vision, not constant so the light helps you see and doesn't enable you to judge speed or direction of the other cycle. These people and the designers who added a flashing mode to their lights should all be shot!

[De Sisti]

...not constant so the light helps you see and doesn't enable you to judge speed or direction of the other cycle.

You see a flashing light in front of you....it's not
exactly going to be coming from a direction behind you.

[[XAP]Bob]

The flashing mode rear lights make life a bit difficult to judge distance because you don't necessarily get time to focus and monitor motion (which is what gives distance judgement, along with stereoscopic separation)... But it is picked up by peripheral vision much better (as it simulates motion in that part of the eye)...

I run a solid front and rear light powered from my dynamo - the rear is always on, the front is switched.
I also have a rear blinky on the seat by my right shoulder for when it is really dark, or misty or otherwise "icky"

I have red retro reflective tape (a stripe down each of my three mudguards), and patches of 3M diamond grade retro reflective - one on the front face of each mirror as well as my German standard front reflector integrated into my centrally positioned light.

I'm happy (based on my experiences over the last three years) that I am clearly visible to all motorists - with the possible exception of when I'm filtering, so I apply extreme caution when I do so.

[james01]

Flashing lights are better at attracting the attention of the viewer
Fixed lights are better at allowing the viewer to establish the distance

.

I LIKE the idea of drivers having to concentrate because they can't establish how near they are to an upcoming hazard when it has flasing lights. Maybe it'll wake them up a bit and they'll approach with caution.

[[XAP]Bob]

Flashing lights are better at attracting the attention of the viewer
Fixed lights are better at allowing the viewer to establish the distance

.

I LIKE the idea of drivers having to concentrate because they can't establish how near they are to an upcoming hazard when it has flasing lights. Maybe it'll wake them up a bit and they'll approach with caution.

No they'll just hit you and say "but I couldn't tell he was that close"

[thirdcrank]

I think there's something different about the appearance of an LED red light - as compared with a traditional rear bike lamp. Going back to the mid-1990's, I was on nights when I saw a red light which seemed a long way ahead. It seemed uncannily bright. At first, I assumed it was a motorbike, but the movement was wrong. It was a cyclist with a new-fangled LED light. The rider was also nearer than I had first thought.

Based largely on that experience, I suspect that the bits and pieces of experiments carried out around that time - largely eith the intention of supporting the official position that flashing lights should be reserved for emergency vehicles - were not comparing like with like in that even comparisons between steady bulbs and steady LED's would have revealed differences in things like judging distance. I suspect also that this is a learned, rather than an inevitable experience. ie I think people were used to seeing one type of light and were confused by another. Rear lamps with bulbs are now so rare that I suspect the confusion would be in the other direction.

As another example of what I mean, "older readers" will remember the introduction of the bright yellow street lights in the 1950's. Colours were completely transformed and the effects were initially quite startling. People were quickly accustomed to them.

[mrjemm]

Just to add an extra element in this, PDW (Portland Design Works- the US definition of Hipster?) produce rear lights that change flash mode seemingly randomly- http://www.charliethebikemonger.com/pdw ... 1912-p.asp

Hopefully to the chagrin of taxi drivers everywhere. They may remind 'em that there are even flashing lights attached to all four corners of their own cars... Not that they ever use them.

[[XAP]Bob]

Illegal in the UK - flashing must be even and between 0.5 and 2 hertz IIRC.

But who gives a monkeys.

[simonineaston]

The number of people who have front lights powerful enough to dazzle you set to flash is ridiculous. In the dark this is enough to destroy your night vision, not constant so the light helps you see and doesn't enable you to judge speed or direction of the other cycle. These people and the designers who added a flashing mode to their lights should all be shot!

As far as I'm concerned the annoyence extends to front lights on 'steady'... Its bad enough cycling towards 1 rider with his 'military-spec' front light beaming straight into my eyes, but facing a group of like-minded cyclists spoils my night-vision for ages... the same group of cyclists would be rightly indignated if an on-coming car driver failed to dip their headlights...