Do flashing rear lights make it easier to judge how far away a cyclist is?

[cycle tramp]

Nor me, although there have been a couple of scarily close incidents, and I sincerely hope it never happens to either of us.

Thank you - y'know if there was a single aftermarket product which would prevent bicycle riders from becoming victims of poor or selfish driving I think we would both unanimously support its use...
...in this case even if other road users can see us and predict our speed with 100% accuracy there is no guarantee we would be treated with the respect that all vulnerable road users deserve...
..... ideally I think we're all waiting for some sort of dynamo powered force field...

[Dupont]

I have a fixed solid light and a flasher and run both simultaneously at night.

[Nearholmer]

ideally I think we're all waiting for some sort of dynamo powered force field...

So true.

The most recent nasty I had was from a driver who absolutely, 100% definitely did see me.

I took roughly the green track, and the car directly behind me took the red track, resulting in it passing so close that part of it went below my right handlebar. I followed it until it parked, and asked the woman driving it (genuinely) very politely “What happened back there then?”. She said she thought I was going to turn left, and when I pointed out that I hadn’t signalled left, or done anything except follow the arrow on the road surface, her answer was “I’m really sorry; I don’t usually do that.” ……. Which I suppose is some comfort!

[Colin63]

I took roughly the green track, and the car directly behind me took the red track, resulting in it passing so close that part of it went below my right handlebar. I followed it until it parked, and asked the woman driving it (genuinely) very politely “What happened back there then?”. She said she thought I was going to turn left, and when I pointed out that I hadn’t signalled left, or done anything except follow the arrow on the road surface, her answer was “I’m really sorry; I don’t usually do that.” ……. Which I suppose is some comfort!

Really like that way of approaching a driver. Unassuming

[Nearholmer]

I did expostulate rather loudly and profanely as the incident happened, but she wouldn’t have heard that from inside the car, and I did tell her she’d better be careful not to kill somebody.

[Debs]

Whenever discussing the benefits (or not) of flashing bicycle lights it is important to know; the rate of flashing, the brightness of the flash (lumens?), and the angle of aim in which the lamp is set upon the bicycle in question.

For examples; a rapid strobe-like flash from a very bright daylight type light, at direct eye contact level, and used in the dark or even at dusk, will cause annoyance or worse a danger with dazzling other road users.

However, a slow rate of flash from a less powerful (but sensible) lumen at a dipped angle will still get noticed and will be far easier for other road users to estimate distance and speed.

[brianleach]

When I used to ride large motorcycles I did not use my headlight during the day. No scientific evidence to this but my perception was that more motorists pulled out in front of me from side roads when I had a headlight on than when I didn't.

It seemed that they thought they could judge my speed from the headlight (which most of them couldn't) whereas without the light they took longer by which time of course I was much closer.

When I used to cycle home from the railway station, in the dark during the winter of course, I went really OTT. I had two rear solid lights and one flashing. Unsurprisingly everyone seemed to see me!!

[Pebble]

from my own view point I think rear flashers are fantastic, can't fault them at all. However it is not me that could be passing me. And from all the comments I have read, clearly some people find them difficult to interoperate distances from, So I now use one steady and one flashing if in a town.

same with high vis, for me it sticks out like a sore thumb, see it from outer space, but that's not much use to me if it doesn't register with the driver behind.

Our eyes and perception must vary

[mig]

Whenever discussing the benefits (or not) of flashing bicycle lights it is important to know; the rate of flashing, the brightness of the flash (lumens?), and the angle of aim in which the lamp is set upon the bicycle in question.

For examples; a rapid strobe-like flash from a very bright daylight type light, at direct eye contact level, and used in the dark or even at dusk, will cause annoyance or worse a danger with dazzling other road users.

However, a slow rate of flash from a less powerful (but sensible) lumen at a dipped angle will still get noticed and will be far easier for other road users to estimate distance and speed.

i have seen alot of this over this winter with front lights. makes me avert my gaze even when cycling (when my eyeline is above the light) but is dangerous when dazzling a driver.

[LollyKat]

Some rear lights are now so big and bright that I think that if the light is steady, there is a risk that drivers will identify the cyclist ahead as a motorcyclist, travelling much faster. Personally I use a solid light together with a medium flasher, together with reflective pedals or ankle bands, to identify me as a cyclist. (Though these days I rarely have to ride in the dark.)

[Psamathe]

Whilst I use flashing front and rear daytime lights, I was recently attending a talk at an event (specialist, non-cycling) and the talk raised the issue of Motion Induced Blindness (MIB). The particular talk was in part presenting the results of sufferers response to the test but it affects everybody to different degrees.

Easy to illustrate. Need computer (not phone nor tablet apparently) and view the image https://psamathe.net/temp_images/2024-0 ... dnessf.gif. View the image (it's an animated gif) and stare at the central green flashing dot. After not long, what happens to the yellow dots in a triangle round the outside? (it will happen to one or two or all three).

It's not in the gif - all three yellow dots are constant, just moving background and flashing central green. Each time you try the results might be different.

Although nobody has suggested any impact or raised aspects in relation to flashing cycling lights it did make me wonder.

Ian

[backnotes]

That's an interesting one - thanks! I can still get the yellow dots randomly disappearing if I put a tiny blob of BluTac over the flashing green dot and stare at that instead, so I'm not sure the flashing of the fixation point is making the difference (for me) here?

[mattheus]

Easy to illustrate. Need computer (not phone nor tablet apparently) and view the image https://psamathe.net/temp_images/2024-0 ... dnessf.gif. View the image (it's an animated gif) and stare at the central green flashing dot. After not long, what happens to the yellow dots in a triangle round the outside? (it will happen to one or two or all three).

Reported to Mods.

Reason? Witchcraft.

[james01]

Recently cycled home on a misty drizzly night on a fast local unlit rural B road with dynamo rear plus flashing battery rear, plus flashing helmet light. Cars could be heard to reduce speed and then cross to opposite lane to pass me. I think that my array of lights made it HARDER to judge distance and worked to my advantage. This was a wake-up call to any inattentive motorist. If they'd been able to judge my position easily I would have had more close passes.

[Psamathe]

Recently cycled home on a misty drizzly night on a fast local unlit rural B road with dynamo rear plus flashing battery rear, plus flashing helmet light. Cars could be heard to reduce speed and then cross to opposite lane to pass me. I think that my array of lights made it HARDER to judge distance and worked to my advantage. This was a wake-up call to any inattentive motorist. If they'd been able to judge my position easily I would have had more close passes.

I've often thought that both constant in addition to flashing a good solution, more visible than either on their own. I thus look for rear lights that support a "pulse" mode where some LEDs are always on, others flash (so you in effect have both forms in a single light).

That said, my current rear does not do the "pulse" pattern as I ended-up going for a really bright flasher for the bent as I only use it daytime (rare night use on tour).

Ian