I recently bought a red and blue flashing light to wear on my helmet when I cycle into work in London.

I abide by road rules, cycle safely, never cycle on footpaths, obey stop signs and traffic lights etc, so my intent here is not to dash through red traffic lights whenever I want.

But it is incredible how much more drivers pay attention to red / blue flashing lights compared to standard white bike lights; I've noticed a measurable increase in how safe motorists drive when they see my red and blue flashing lights, from slowing down, to actually indicating when turning (a rarity in London) and giving ample room on the inside lane to me as a cyclist.

I appreciate that some people may think of this as "trickery" and that I am decieiving motorists into thinking that I am emergency services so that they drive on their "best behaviour". That is not my intention. My intention is to make cycling as safe as possible, which in London, where there aren't very many protected cycle lanes, is crucial to preventing accidents.

I only turn it on when I share a road lane with no protective barrier with motorists (which is about 60% of my commute); as soon as I get into a protected bike lane I turn it off. I don't want to have to use the light, but if its a question of safety or some people confusing me for emergency services, I would rather choose the former.

I have two questions:

  1. Is it legal under UK road law for bicycles to use red / blue flashing lights? I read in a road law handbook that motor vehicles cannot use them for obvious reason, but bicycles...?
  2. Provided it is legal, is it moral to do so? Yes, there is an element of deceiving drivers, which is not the direct intention. But if it makes motorists drive safer, ensuring a safer road expereince for all road users, what is the issue?
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    I'm surprised noone has tried strobing amber lights as used on council vehicles, construction vehicles etc. No legal problem there.
    – Noise
    Commented Dec 14, 2021 at 16:27
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    @ChrisH bleurgh - excellent way for them to ruin a good idea. Perhaps a web-form might work better, from one of the listed google results.
    – Criggie
    Commented Dec 15, 2021 at 7:40
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    The London Ambulance cycle responders have blue/white flashing lights fitted, I don't know whether other ambulance services do as well. I wouldn't want to give people false hope I might be a paramedic.
    – thosphor
    Commented Dec 15, 2021 at 12:23
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    @Criggie If that fails, wear the lights while flashing as you go by a bored looking policeman... if they don't stop you your probably good, if they do you can explain. ;-)
    – Michael
    Commented Dec 15, 2021 at 14:17
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    I'm surprised this hasn't been linked: Can I legally use front facing blue light in the UK? This question is awfully close to duplicating that one. Commented Dec 15, 2021 at 15:00

6 Answers 6


Don't show a red light of any kind on the front unless you want a head-on crash.

Red is for the back only, steady or flashing. In the shadows it will look like you're riding the wrong way down the street and confuse everyone. As a worst case consider narrow roads where any cyclist will be in the middle to avoid the doors of cars parked on both sides. A flashing red light on the back is legal, and a good idea, though probably unhelpful as your only rear light (it's not as easy to track something moving if it's flashing). It should also be set up so as not to dazzle a following cyclist. That can be tricky in cities when you want to show up to cars, but is doable.

The blue is probably illegal (The Road Vehicles Lighting Regulations 1989): "No vehicle, other than an emergency vehicle, shall be fitted with ... a blue warning beacon or special warning lamp". I say "probably" because in some contexts (though not, I believe, this one) bikes are excluded from the definition of "vehicle".

  • 6
    Agreed on both, particularly blue lights based on legislation.gov.uk/uksi/1989/1796/part/II particularly part 16 . The exemptions are clearly spelled out for pedal cycles and for blue lights there is none.
    – eps
    Commented Dec 15, 2021 at 6:14
  • @eps Well found. That would also appear to rule out rear-facing amber lights and indeed rear-facing non-red retro-reflectors unless on pedals or wheels (I'm not sure how that would relate to reflectors on panniers for example, and of course I won't be removing my deep orange extra reflective material from my mudguard
    – Chris H
    Commented Dec 15, 2021 at 9:20
  • The most attention that i've paid to a cyclist was a strong strobing light. white means forwards and red means back. Commented Dec 15, 2021 at 19:39
  • @LifeInTheTrees that's certainly eye-catching, but can cross the line to dazzling very easily. I used to have a narrow-beam headtorch on my helmet, which I could use to make absolutely sure I was noticed, though it normally illuminated the way well ahead (mainly an unlit bike path that had a sharp bend or drop into a lake and people walking dogs off the lead). Strobing rear lights on the seatpost or similar height are horrible for cyclists behind, but on top of a helmet they work well - less in the line of sight of a following cyclist, and even more visible to approaching cars
    – Chris H
    Commented Dec 16, 2021 at 8:50
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    @LifeInTheTrees a significant minority of bike strobes here are far more dazzling than a car headlamp, unless the headlamp is being misused by not being dipped in the presence of other traffic. Partly that's poor aim, which can even be due to road vibrations, but some light are designed so that someone a mile away can see that something's there, but not identify or precisely locate the something. That doesn't help anyone. Very bright things can be very good, used carefully. And I bought several cheap hi-vis jerseys for winter commuting; if I need a jacket that's hi-vis too
    – Chris H
    Commented Dec 16, 2021 at 10:48

Legality aside, this is a bad idea.

The entire point of putting distinctly colored lights on emergency vehicles is to make them instantly recognizable as such, letting people know that they need to make way for the emergency vehicle. By placing them on another vehicle, you are desensitizing people to these important warning indicators. This desensitization could easily lead to slower response times for emergency vehicles, making the road, and all of the surrounding area more dangerous for everyone.

If you'd like to make yourself more visible without using blue lights, check out this answer which focuses on steady state vs. flashing lights.

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    Interestingly, in London road users are so desensitised to emergency sirens that the VIP transport branch of the met (the Special Escort Group) use whistles to get attention.
    – Tim
    Commented Dec 15, 2021 at 1:30
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    @Tim interesting... and when people are desensitized towards whistles I suppose they will use barking dogs!
    – Michael
    Commented Dec 15, 2021 at 14:18

Restrictions on fitting blue warning beacons, special warning lamps and similar devices

16. No vehicle, other than an emergency vehicle, shall be fitted with

(a) a blue warning beacon or special warning lamp, or

(b) a device which resembles a blue warning beacon or a special warning lamp, whether the same is in working order or not.


  • I wonder if police bicycles use blue warning beacons in the UK?
    – gerrit
    Commented Dec 17, 2021 at 8:45
  • There is also the question of whether a light worn on the body of a rider is considered to be "fitted to a vehicle" or not. My understanding is that it isn't but i'm not 100% sure on that. Commented Dec 17, 2021 at 20:05
  • @PeterGreen that was certainly a common reading of the rules before before flashing (red/white) lights were allowed on the bike. It's also logical. But as far as I'm aware it's never been put to the test. Even so it may be enough to get stopped (and given some hassle though probably no more than that) for impersonating the emergency services
    – Chris H
    Commented Dec 20, 2021 at 11:15

Related - I used to have a small flashing LED on my dog's collar when out walking at night, and it was red/white/blue.

Gave it up after a few months because it got all sorts of attention, like yobs and drunks asking if he was a police dog. The end was when one entirely sconsed chap took a kick at the dog for being "a pig" (he missed and fell over, dog was fine)

Perhaps this is not the kind of attention you want to attract while out in public on your bike.

  • 1
    Round here I wish I saw more illuminated collars (ideally the whole collar rather than just a dangly light that can only be seen from in front). Some of our bike paths go through unlit parks, and illumination is better than reflection on something than can approach rapidly from off to the side. Blinking blue may not be the best option, but with people like that around, who knows what will set them off?
    – Chris H
    Commented Dec 15, 2021 at 12:02
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    The best illumination scheme I've ever seen was some dude who covered his entire frame with white LED's. It was quite impressive although I'm not sure if it was legal or not :) Commented Dec 16, 2021 at 3:59
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    @DavidWaterworth probably not (white showing to the rear) but I've got ideas involving electroluminescent wire
    – Chris H
    Commented Dec 16, 2021 at 16:06
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    @DavidWaterworth, the best illumination scheme I've ever seen was a bicyclist wearing a road worker's safety vest. Huge reflective stripes that I could easily see from a quarter-mile away.
    – Mark
    Commented Dec 16, 2021 at 22:36
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    @Mark yes that's true on lit roads or when a car approaches with headlights, in general I agree a good reflective scheme makes you much more visible than any light. But I was mainly replying to the comment regarding illumination on unlit paths, where reflective vests don't work so well. Commented Dec 16, 2021 at 23:07

To contribute an underlying question of your question: how to "stand out" as cyclist in the dark when from the point of view of a driver's mirror (it's a bit too long to be written as comment, and may be of interest).

In some countries (at least France and Belgium), the front light of a bike light can be white or yellow. If yellow lights are legal in the UK, it can also be a solution, as a single yellow light is more likely to be noticed than "another white light".

During my last stay in the Netherlands, I also noticed that a significant amount of bikes have front lamps (white) mounted on the fork, on each side. It also creates a distinct visual signature, that is clearly distinct from a car one.

Fork Mounted Light



I suppose they are thinking that it's a cop bike in an emergency.

In the link above there's an example in Italy, but I suppose it's possible that the same idea could pop up in UK. So as someone has already said it's illegal.

But, on the other hand imagine if a motorist thinks to do the same and basically impersonates an unmarked cop car. People seeing a car with blue flashing lamp are normally going slower and it's going to be safer for the wanna be cop car.

Ask yourself: do you want to impersonate a cop?

Better idea is use a big red light non flashing on the rear, with a big red reflector and a white light on the front, possibly that illuminates the road in front.

  • I would call the police if I saw a cycling impersonating a police officer.
    – gerrit
    Commented Dec 17, 2021 at 8:46

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