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

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oldcycleguy
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Joined: 21 Apr 2012, 10:27am

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

Post by oldcycleguy »

Pensioner returning to cycling for fitness, and afraid of being knocked off, consequently I was thinking of fitting a flashing rear LED to the pannier, and possibly a flashing front LED. However, I was wondering if they do any good and if they annoy drivers? Can they confuse a driver about the speed that a cyclist is traveling at? I remember when I was young, a driver pulled up alongside me and said “do you know you are doing 30 mph”! It’s unlikely that I can cycle that fast now but I expect that I can get up a fair lick.
Rides Raleigh Routier with improved spec.
IanH
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Location: Wellington, Somerset.

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

Post by IanH »

I think it's a good idea, especially on a busy road in poor light conditions. Just like high vis clothing, it improves the chances of a cyclist being spotted early and appropriate action being considered early.
Pete Owens
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Joined: 7 Jul 2008, 12:52am

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

Post by Pete Owens »

A rear light wont make any difference during the day - drivers most certainly can see you and have plenty of time to notice as they approach.

The problem with SMIDSYs is mostly in front of you - drivers trying to spot a gap in busy traffic as they try to join a busy road and having to make quick judgement. A flashing front light conceivably might help for these situations.
freeflow
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Joined: 29 Aug 2011, 1:54pm

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

Post by freeflow »

In poor light conditions you should be using full lights.

The problem with hi Vis gear is that it doesn't eliminate the problem of 'seccades', i.e. drivers not looking long enough to register what is actually visible rather than what their brain is assuming is visible.

So best practise for cyclists is eternal vigilance.
mattsccm
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Re: Is a flashing rear light during the day a good idea?

Post by mattsccm »

Probably in some cases.
ndmbike
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Joined: 1 Oct 2011, 12:45pm

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

Post by ndmbike »

It depends.

There is a stretch of road that I drive and sometimes cycle on.
A steady cycle light looks like a motor vehicle light - but a flasher shows it is a cyclist.
It means at 50 mph in a car I can plan the overtake of a cyclist by moving into the second climbing lane and give the cyclist a wide berth.
As a cyclist it is terrifying to have a big car blast past without enough room.
Some cars seem to do over 80 mph on this stretch.

Other times it feels like the flashing light is unnecessary and even a distraction. Who knows.
If it means a cyclist does not get squished under the wheels of a Chelsea tractor it must be a good thing.
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simonineaston
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Re: Is a flashing rear light during the day a good idea?

Post by simonineaston »

Agree no advantage to daylight lights, at all. Recall too that research indicates flashing lights (regardless of colour) are harder for viewer to assess distance, thus at night, two red lights at rear, one flashing, the other steady, can be beneficial.
(rides: Brompton nano & ever-changing Moultons)
Psamathe
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Re: Is a flashing rear light during the day a good idea?

Post by Psamathe »

I'd be interested in any actual data about the effect of day lights (both front and back). On my DF I don't use them daytime in good weather. On my bent I do and have got myself a particularly bright rear pulse flash one (Lezyne Strip Drive Pro https://ride.lezyne.com/collections/led ... -drive-pro - reviews on internet say don't use full power at night). But I can't say if it helps as early days and I've had no issues but you never know if the light helped or not - need research. i.e. on either bike I have relatively few "incidents", not enough to make any counts useful or indicate anything.

Ian
PDQ Mobile
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Re: Is a flashing rear light during the day a good idea?

Post by 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.
axel_knutt
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Re: Is a flashing rear light during the day a good idea?

Post by axel_knutt »

PDQ Mobile wrote: 25 Sep 2021, 8:21pm 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 did an experiment. Compare flashing and continuous, and count what percentage of cars pull over far enough for the nearside wheels to cross the white line. I can't remember the actual figures now, but there were far more with the light flashing.
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Grandad
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Location: Kent

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

Post by Grandad »

The eyes need to adjust when going from bright sunlight into dark wooded lanes, even more so if wearing sunglasses. A flashing rear light offers some protection against temporarily blinded motorists.
oldtimer99
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Re: Is a flashing rear light during the day a good idea?

Post by oldtimer99 »

Not sure that there's a definitive answer. I don't ride at night and almost all of my rides are on rural roads. Lots of drivers going fast on sometimes quiet roads.
I always ride with flashing lights front and rear. Rechargeable and bright.
I feel happier and that's a big thing as I'm sure that it 'wakes up' a few drivers each ride and that's just fine.
When I'm driving, I can see flashing lights well in advance (not round bends!) and have time to prepare.
Can't think of a reason not to use them
millimole
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Location: Leicester

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

Post by millimole »

PDQ Mobile wrote: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.
This is my impression.
I don't wear hivis, but do use a high powered rear flashing light in daylight.
I'm convinced I get more space on Leicestershire roads (could be confirmation bias)

My opinion is that hivis being 'passive' fades into the background for /some/ drivers, but the 'active' flashing pushes the object into the foreground of consciousness for /all/ drivers.

I don't believe there's any scientific work on daytime lights, so it's all opinion and conjecture. Any opinion - including mine - is as good as the next.
Leicester; Riding my Hetchins since 1971; Audaxing on my Dawes; Riding to work on a Decathlon Hoprider
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Audax67
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Re: Is a flashing rear light during the day a good idea?

Post by Audax67 »

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.
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toontra
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Re: Is a flashing rear light during the day a good idea?

Post by toontra »

I'm pretty sure I'm given more space with a flashing rear. I use a Garmin "Radar" which has the added feature that when a vehicle approaches the rate of flashing increases.

Did 100 miles on the A4 yesterday and not a single close pass, many drivers going to the opposite carriageway when possible.

(NB. The Radar also lets me know when a vehicle is approaching on my computer - handy in some cases).
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