Is a flashing rear light during the day a good idea?

[PDQ Mobile]

My entirely personal feeling is that I get given more room from passing vehicles when I show a flashing daytime light on fairly narrow Welsh A and B roads.

I can imagine that effect would probably withstand scientific scrutiny. I wonder if anyone's done that sort of research. The trouble is, as has been suggested upthread that the sort of light that's visible in daylight, is also likely to be so bright as to have negative effects on those who may look into it, at night.
I'm at my wit's end to work out what goes through some bike/light users minds that I meet on cycle paths - not so bad on roads as the angle between oncoming bikes is wider. Surely it must have dawned on them that the super-bright light they have sort out has 2 connected properties 1) they are highly visible and 2) they can and often do, dazzle the oncomer, or follower, regardless of the type of vehicle the party is using, thus making it harder for them to see where they are going !! Same is true, but to a lesser degree, when said lights are used in daylight.

i was only referring to rear lights.
I use one "bog standard" 3 LED type.
It's quite bright but not blinding.
Three settings. Constant. All 3 flashing. And an across the light type flashing.

I consider flashing an advantage over constant, for a number of reasons already stated by others in the thread.

I do have a similar type of front light, that is cheap but bright enough to negociate unlit lanes.
I sometimes use a flashing mode in daylight. It is done and decided on the basis of prevailing road conditions.
Otherwise just as a normal light at night.

[rareposter]

I always have a flashing red light displayed, and in wet/poor conditions I have 2 on (I try to make sure they are out of sync).

It doesn't save me from every close pass but I'm sure most drivers give me extra room because of it.

Back in the days when I was doing daily commutes, I always had two rear lights, more for the fact that I had a backup if required. Rarely used both together but knowing that I had two working rear lights was a great peace of mind. The only "failure" I ever had was one running very low on battery as I'd forgotten to take it from the bike shed at work into the office to charge but the other one was near full charge so no actual issues.

Sometimes when my commute was that weird half-light you get at dawn/dusk, I'd use one on constant, one on flashing.

[ChrisP100]

I always have a flashing red light displayed, and in wet/poor conditions I have 2 on (I try to make sure they are out of sync).

It doesn't save me from every close pass but I'm sure most drivers give me extra room because of it.

Back in the days when I was doing daily commutes, I always had two rear lights, more for the fact that I had a backup if required. Rarely used both together but knowing that I had two working rear lights was a great peace of mind. The only "failure" I ever had was one running very low on battery as I'd forgotten to take it from the bike shed at work into the office to charge but the other one was near full charge so no actual issues.

Sometimes when my commute was that weird half-light you get at dawn/dusk, I'd use one on constant, one on flashing.

I used to have one of those old 3v double D-Cell Ever Ready grey boxes on the back. I'd be lucky if the batteries lasted more than a week. I always had at least 2 batteries. As for brightness...

[Bonefishblues]

I always have a flashing red light displayed, and in wet/poor conditions I have 2 on (I try to make sure they are out of sync).

It doesn't save me from every close pass but I'm sure most drivers give me extra room because of it.

Back in the days when I was doing daily commutes, I always had two rear lights, more for the fact that I had a backup if required. Rarely used both together but knowing that I had two working rear lights was a great peace of mind. The only "failure" I ever had was one running very low on battery as I'd forgotten to take it from the bike shed at work into the office to charge but the other one was near full charge so no actual issues.

Sometimes when my commute was that weird half-light you get at dawn/dusk, I'd use one on constant, one on flashing.

I used to have one of those old 3v double D-Cell Ever Ready grey boxes on the back. I'd be lucky if the batteries lasted more than a week. I always had at least 2 batteries. As for brightness...

I was dead hi-tec, I used rechargeables and brighter bulbs so there!

[NUKe]

I would say to the original OP it wont harm, if it makes him feel safer.
However the best way to feel safe is to ride assertively. using your road position and keeping control.
You might want to find a local group and ride with some more experienced riders or see if there is a bikeabilty course in your area.

[mattheus]

They're horrible to ride behind. You can almost ignore them by day, by night the low-power ones twist the eyes out of your head while the high-power ones blind you. For me, until they produce one with built-in radar to switch the thing off when another rider comes up behind they're such bloody bad manners I won't have one.

Unfortunately, not everyone agrees with me.

Well I agree!


I also think they are bad for road-users in general - they fail one of my standard tests:

What if everyone used them?

(bad in an area with a lot of cyclists... but also imagine if the Motons get hold of the idea. Look how much they love using foglights ...

[Jules59]

So best practise for cyclists is eternal vigilance.

Especially at junctions where CBDR means, sometimes, you are always in their blind spot, even as you get nearer. I like to see if we make eye contact.

I do they same thing when I'm driving.

[mjr]

Back in the days when I was doing daily commutes, I always had two rear lights, more for the fact that I had a backup if required. Rarely used both together but knowing that I had two working rear lights was a great peace of mind. [...]

Surely cyclists should mount their primary back light where they can see them (back of the rack, for example) and look around often enough that any failure will be noticed within a minute of occurring?

Failures are pretty rare with modern LED lights with battery indicators. Better one good light than two junk.

[rareposter]

Back in the days when I was doing daily commutes, I always had two rear lights, more for the fact that I had a backup if required. Rarely used both together but knowing that I had two working rear lights was a great peace of mind. [...]

Surely cyclists should mount their primary back light where they can see them (back of the rack, for example) and look around often enough that any failure will be noticed within a minute of occurring?

Failures are pretty rare with modern LED lights with battery indicators. Better one good light than two junk.

I had two good lights - Exposure Flare. Sealed LED light with USB rechargeable battery. Frankly I have better things to do while riding an urban commute than look down at my seatpost every few minutes to check a light is working. They both just work. The one issue, as mentioned, was forgetting to charge one of them up once but that's not a problem with the light, that's an occasional human error and that's the whole point of having a backup.

But that is going off-topic to the original question.

[Psamathe]

I wonder if their effectiveness depends to an extent of the type of roads you are cycling on. In a busy city with loads of other bikes (and thus flashing things everywhere) maybe not as helpful. But on quite bendy country roads where you might be the only cyclist around might they be more effective to highlight your presence to a less attentive driver (I appreciate that responsibility is on drivers to be fully attentive and it's not the responsibility of cyclists to make-up for drivers with their thoughts far away from driving - but they do exist and I'd rather not be the individual who suffers the outcome of such a driver ...).

(nb. I don't use daytime lights n my DF, just on my bent and I'm new to bents so still getting to appreciate driver reactions, etc. and it does seem different).

Ian

[mjr]

Frankly I have better things to do while riding an urban commute than look down at my seatpost every few minutes to check a light is working.

That is one reason why the seatpost is a bad place for a light and it should be where you can see it when you look backwards, which should be often, especially on an urban commute. That was part of a point in my previous post.

There are other reasons seatposts are bad places for lights.

[drossall]

I have a sneaky suspicion that these two questions are not the same, but that people do not differentiate between them:

• If I fit daytime lights, will I be safer? (Probably, yes)
• If everyone fitted daytime lights, would overall safety improve? (Probably no, it would get worse, because of all the distraction)

So I'm not keen on the assumption that we all need daytime lights. But the point above about flashing lights being poor for judging distance (to the light) is probably not relevant in daytime, as you can see the bike anyway. The point is that, at night, the light can be the only thing to which distance can be judged.

[David2504]

Anything that could potentially catch a motorist’s eye and thus increase your visibility is not a bad idea. I imagine 99.99% of the time a flashing back light will make no difference but sooner or later that one occasion when it catches they eye and saves you from serious injury or worse will come around.

[drossall]

Which of my two questions were you addressing?

[mattheus]

Anything that could potentially catch a motorist’s eye and thus increase your visibility is not a bad idea. I imagine 99.99% of the time a flashing back light will make no difference but sooner or later that one occasion when it catches they eye and saves you from serious injury or worse will come around.

An automatic firework array/detonator would satisfy this criteria.