rear cycle light a bit too bright

[eric_james]

Hello. I got my Son a new rear bike light it's a cateye viz150. I think it might annoy car drivers, I couldn't seem to adjust the bracket to point it down unless I'm not doing it right. was thinking of some kind of tape on it a bit like medical tape but black maybe I don't know

 

[foz]

Does it not have various different brightness settings?

 

[novocaine]

no such thing as a rear light that's to bright, it will still be dimmer than a 12v brake light (and considerable dimmer than a high intensity rear light). don't modify it.

 

[Chopper the ex Copper]

It annoys car drivers?

I'll have two!

 

[eric_james]

It just has different flash settings I have seen that light dimming tape. It's just I see these cyclists with very bright lights so I always make sure front lights are set correctly. This light replaced a small old style 3 LED cateye rear light

 

[synchronicity]

It can never be too bright (during the daytime).
You want cars to:
a) notice you, then
b) give you more space when overtaking.
That's the whole point.

Better yet, get the Cateye ViZ450!

 

[novocaine]

It just has different flash settings I have seen that light dimming tape. It's just I see these cyclists with very bright lights so I always make sure front lights are set correctly. This light replaced a small old style 3 LED cateye rear light

Front lights I agree with, rear lights, nope, bright as possible and ss many doing different things at different heights as possible. I have one on the back of my lid, one on the seat post (2 at the moment).

 

[Chopper the ex Copper]

It can never be too bright (during the daytime).

Actually it can, in particular the front light.

Honda, who own one of the world's largest searchlight manufacturer so have first class expertise in optics to draw upon, and Suzuki did research into daytime light usage in thec1980s, just as DRLs started to become a thing with by legislators.

Having analysed thousands of daytime motorcycle collisions they discovered that daytime headlight usage - as opposed to proper DRL's or dim/dip systems - were actually more likely to have a smack, particularly in T bone scenarios where another road user would pull out in front of them.

How can this be when lights are supposed to increase conspicuity?

The observers brain determines an oncoming vehicles speed by the rate at which the outline appears to grow in relation to the static background. It turned out that dipped headlights in the daytime were sufficient to break up that outline and thus deprive the observers brain of the necessary datum required to make an accurate calculation of another vehicles speed. Remember that this was the 1980s when 55w headlamps were pretty feeble compared to the computer optimised LED and xenon lights of today, so in 2023 the effect of dip beams would be far worse.

Once you're aware of this phenomenon you can see it at work first hand. You will see motorbikes with their headlamps on during the day (as opposed to just the DRLs) and you can watch for yourself how the light obliterates the silhouette. Increasingly I'm starting to see cyclists with plutonium powered lights on during the day and the phenomenon can be seen with them too.

Another example of how perceived wisdom rarely actually translates positively to matters of safety, and can even have a detrimental effect. Lights by all means during the day, but something akin to sunrise over Hiroshima is actually placing riders in greater danger by making it harder to judge their speed, movement, and in some extreme cases even the nature of the vehicle.

For my next safety lesson we'll talk about the use of fluorescent clothing outside of urban areas...

 

[synchronicity]

Actually it can, in particular the front light.

I meant the rear light.
Many drivers claim to have never even seen the cyclist at all! Apparently we just blend into the background (or something).
More likely is that car drivers are simply not making an effort to look out for other road users, in particular cyclists and motorcyclists.
In those situations, bright [rear] lights help us to stand out on the road ahead. Drivers get more notice that we're there.

I drive too and I've noticed that a cyclist with a super bright light is visible far earlier in the distance than one without (or with a dimmer light).

Speaking from personal anecdotal experience, cars have smacked into me twice now during the daytime when I wasn't using any lights.
Both were approaching from the rear.

For the front light, I am just using a Bontrager ion, which is only one or two hundred lumens at most. Not very bright.

 

[Chopper the ex Copper]

I would guess - and it is just a guess as I have no expertise - that rear lights don't pose quite such an issue as they would generally be travelling away from the observer.

Nevertheless, the same optical principles apply so I could foresee problems in a traffic rich environment where the rider might be manoeuvring or changing direction - anything that compromises a close-by motorists ability to judge speed and direction quickly and without extra effort is probably not good.

Multiple decent lights rather than one almighty great CERN powered job is the way forward, spaced as far apart as possible (3 in a triangle is ideal, but 2 is better than one) is the prime arrangement. Not only does it provide 2 or 3 light sources (and a backup in place in case one should fail while oj the move) but as a following driver approaches the apparent increase in distance between the lights as the riders visual size grows in their field of view helps give the brain additional datum to make a decent speed and direction calculation.

It's an interesting and very unintuitive mix of physics, optics, human mental processing and behavior.