The truth behind Hi-Viz

As we all know, High Visibility clothing is seen as a must have safety item for cyclists. With the biggest selling items being jackets and rucksack covers.

High visibility clothing or fabric is made up of a fabric which is bright in colour and often has fluorescent properties, in addition there are reflective strips. The fluorescent properties of the material only work in natural light and the reflective strips only work if a light source is shining on it.

Fluorescent clothing works best during hours of natural light because the clothing ‘converts’ ultra-violet light into visible wavelengths, which makes it appear brighter than other colours and objects. It’s noted that it stands out considerably during poor conditions, such as rain and fog. Light from non-natural sources doesn’t contain much ultra-violet and thus the fluorescent properties of the clothing provide no advantage against non fluorescent clothes.

In most cases, the reflective panels on hi-viz clothing are designed to reflect light back at the source, in a handful of cases the reflective panels reflect light in all directions, this usually weakens the appearance of the reflected light. The more common type of reflective material (known as retro-reflective), reflects light at only a few degrees. So the performance of a reflector can appear very different from the perspective of a lorry driver vs a car driver. As the observation angle increases, the performance of the reflector drops.

So hi-viz is made up of two parts, one being good for day time visibility and one being good for night-time visibility. But they have their drawbacks. With growing numbers for road users being seen wearing fluorescent clothing it can have the effect of making you blend in with others and thus not standing out from the crowd, not the effect you always want. The retro-reflective material only reflects light back at the observer if they shine light at it.

The limits to retro-reflective material can be seen quiet clearly in the pictures below. Due to car headlights shining no higher than the waist of the average person. Any retro-reflective material won’t shine back a strong light because there isn’t much shining on it. In one of the pictures I lower the hi-viz cover into the headlights of the car and quiet clearly there is a difference between the two.

High visibility clothing is obviously great for standing out. After all that is what it is designed for. Cyclists in a busy city have to weigh up the options. At night the Hi-viz jackets and rucksack covers are next to useless unless you have rolling hills. During the day they can help you stand out but if you get into a group of other cyclists you may blend in, which can result in someone miss-reading your speed.

During the day I think it is personal choice about wearing hi-viz jackets, I personally don’t, I would much rather turn my lights on than wear yellow.
During hours of darkness I don’t see the point in wearing hi-viz jackets, it adds limited visibility. You would be much better off wearing retro-reflective on the legs and feet. Not only are these in the headlight zone of a motorised vehicle but they also move as you pedal. Adding in a much more attention grabbing effect.

16 thoughts on “The truth behind Hi-Viz

  1. Interesting points, fluorescent jackets alone are useless after dark, the reflective stripes are what works at night and as you say the more it is in a light source the better it reflects. I am an avid believer in pedal reflectors as they have to be the most noticed reflector on a bike due to their movement and low position.

  2. I think there is also a sense in which hi viz and to an extent reflectors characterize us as cyclists. Now i am not going to say what you think I am going to say!

    What is this big thing some “safety” conscious cyclists have with being “recognised as a cyclist”………. Why??????

    I want to be recognised in a generic sense as a vehicle using the road, not as a cyclist per se. I honestly think that your typical hi viz clad Christmas tree cyclist is the one that is targetted by the cyclist hating motorists that will run you off the road given half a chance.

    Id rather be 100 % black with a massively bright set of NON flashing lights front and rear and NO reflectors. That way I get mistaken for a slow moped, not a fast Christmas tree/sitting duck!

    The above is borne of experience.

    1. “What is this big thing some “safety” conscious cyclists have with being “recognised as a cyclist”…”

      In the dark it’s hard to see shapes, and thus recognize what it is that you’re seeing. “Being recognized as cyclist” means that the other road users notice that there is a cyclist on the road, instead of pedestrian, a tree, parked car or some other street clutter. If they think you’re a bollard, they will ignore you, and not expect you to move, change lanes or turn.

      The movement of reflective straps on the ankles, reflectors on the pedals and spokes make it easy for other road users to notice and recognize you. On the other hand, if you have enough lights to make the others notice you, that’s good. Like you said, they might think you’re a moped, but that’s close enough and they’ve seen you.

      1. To me an extra set of lights set on flash says “cyclist” far better than a flouro reflective top that may or may not be hit in the right light (pardon the pun). A good set of lights gets seen in far more angles than any coat ever will.

        I personally think this works better when approaching waiting traffic at junctions, as their headlamps wont be shining in your direction.

      2. the point I was trying to make was , of course I want to be identified as a vehicle on the road. But a good set of bright lights front and back do that! What I have found is that too many reflectors, blinking lights and fluoro immediately identify you as a cyclist as distinct from other road vehicles. In my book thats not a good thing. Too many motorists exhibit neurotic symtoms as soon as they realise they have a cyclist in front of them. this neurotic behaviour often endangers me.

        1. Well, if you have lots of obsessive-compulsive “must get ahead”, SMIDSYs and others on the road, camouflaging as a moped might be a good choice. ;-P

  3. I don’t agree that hi-vis jackets are useless after dark. Fair enough, they work best if caught in the vehicle headlights. But even if they’re not directly in the headlights, they still improve visibility. Just check out the picture above: the hi-vis doesn’t stand out as much when raised above the beam of the headlights, but it is still a lot easier to see than the dark jumper.

      1. The article states, “At night the Hi-viz jackets and rucksack covers are next to useless unless you have rolling hills.”

        It doesn’t say the fluoro effect is next to useless, it says hi-viz jackets are next to useless.

        In general, I think the article makes a lot of valid and interesting points but, as I said earlier, I would challenge this particular conclusion. In the right hand picture the hi-viz clearly stands out when compared to the other clothing i.e. it improves visibility at night, despite the fact the fluoro effect is not at its highest. It doesn’t really matter if the improvement is down to the colour.

        1. Flouroescent colours stand out more in the day time than others because they reflect UV light back in a wavelength that the human eye can interpret. This has no effect at night as out lighting technology does not emit UV light.

          As has been said, it won’t stand out anymore than another light colour. Perhaps I could have worded it differently or taken the picture whilst wearing a better top. But a red, white or any light colour will stand out just as much as a hi-viz jacket during dark hours.

  4. As it happens, we don’t all know that fluoro is essential.

    In fact, most of the worlds happy people on bikes know much better.

    If fluoro is the answer, then you’re asking a pretty lame question.

    Do Danes wear fluoro? Japanese? Dutch? Germans? Africans? Indians? Chinese? And notably, the countries with the best cycling safety records have no hi viz required. Nope – it’s only in the English speaking world where we adopt such a victim culture as to assume all the responsibility for drivers who can’t be bothered to out for more vulnerable travellers, and governments for not making them take responsibility, as in more enlightened parts of the world. (In the Netherlands and

    Nothing will get better for people on bikes in low cycling modeshare regions, while they are told to suck it up and wear road worker clothing. The ONLY thing that makes cycling safer to any significant degree is more people on bikes. And that only happens when cycling is seen as an normalized, safe activity. Not something for ‘cyclists’ – whoever they are. To achieve that we need both infrastructure and a culture change, a serious repositioning of cycling as an aspirational, comfortable, easy activity. In the english-speaking world (again, I really don’t know why we in particular have screwed it up so badly) – having a little humility and enjoying our inner euro is a great place to start.

    We got to like their coffee, their food, and their damned fine wine, and now its time to find out how uncrap their cycling culture is. There’ll be no looking back.

  5. What I find strange about calls for cyclists to wear hi-vis is that the vast majority of all road accidents are multi-vehicle collisions. If the crashing driver can’t see an entire car (which have lights much more powerful than bike lights), then how on earth can someone think a little bit of fluro on a cyclist will make them more visible than a car or truck?

    Perhaps a better idea would be to make the perpetrator, not the victim of harm take preventative. measures.

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