The Science of Staying Visible to Other Road Users

In Cycling, Outdoor, Running, Tech / Gear, Performance

Anyone who has taken a primary school cycling proficiency test will know the importance of staying visible to traffic while out on a bike. The uniform of an over-sized hi-vis yellow vest with reflective stripes is a major fashion embarrassment for kids, which puts a real dampener on the otherwise joyful experience of riding a bike.

But dressing and accessorising appropriately when you are exercising in public spaces is crucial and it is as important to be aware of how visible you are during the day as it is after dark, because low sunshine, fog and driving rain can impair a motorist’s vision almost as much as the darkness.

The market is now awash with clothing and accessories for cyclists, runners, outdoor enthusiasts and even walkers and their four-legged friends, claiming to increase their visibility (and therefore keep them safer) while out and about, but do you know the science behind the lingo? Do you know your hi-vis from your electroluminescent, your reflective from your retro-reflective and your lux from your lumens?

Inspired by the complete lack of decent, visibility-enhancing kit available for their cycle commutes in London, brothers Anthony and Rupert Langly-Smith started Proviz in 2009. Their aim was to create a range of clothing and accessories that not only made cyclists more visible to motorists during rush hour, but also looked good and performed well as sports kit too.

Filling a clear gap in the market, their core REFLECT360 collection is now synonymous with safety, but also with style and sporting performance. With well over a decade’s experience of creating and improving such specialised kit, the Proviz team now has a wealth of knowledge about the science of enhanced visibility. Given that this is a bit too niche to give us a competitive edge at any pub quizzes, we thought we’d share some of it with you, to help inform your decision when purchasing your next bit of enhanced visibility gear.

How does fluorescent material work?

Unlike conventional colours (which reflect and equal or lower amount of energy), fluorescent colours can reflect more than 100% of the light energy falling on them. This means that they appear to glow under ultraviolet light, such as the ultraviolet rays present in sunlight, and stand out from their surroundings immediately. Fluorescent garments are less effective in cloudy, foggy and drizzly daytime conditions and at dawn and dusk, when natural light levels are low, but they are still more eye-catching than non-fluorescent colours in the same conditions (and a hundred times better than black).

worker in hi-vis jacket at London Bridge Station

Which is the most visible fluorescent colour?

To complicate matters further, some fluorescent colours work better than others for safety gear. The most common fluorescent colour worn by construction workers, refuse collectors, police officers and HGV drivers is yellow, although orange is also used, especially in maritime safety clothing, as it stands out most prominently against the blue-grey colour that our eyes perceive the sea to be.

Horse riders often wear fluorescent pink, as they are usually out and about in rural environments and bright pink is a colour rarely found in nature. By wearing fluorescent pink they can rest assured that they will clash with their surroundings and stand out to motorists and other road users.

Fluorescent blue clashes least with the natural environment and its short wavelength means that it emits less light. If your favourite cycling shorts or running leggings are blue, be sure to add a more standout fluorescent to your outfit, especially in poor conditions, to increase your chances of being spotted by everyone else on the road, in plenty of time to react safely and appropriately.

What is hi-vis clothing?

Hi-vis (or high-vis, high-viz or hi-viz, depending on your spelling preferences) garments combine the power of brightly coloured fluorescence and reflectivity to make the wearer as visible as possible when out and about. The fluorescent element makes you more visible in daylight and the reflective part helps to make you more visible at night.

Traditionally, hi-vis clothing has been made from fluorescent material with reflective elements sewn or printed on to it that are grey during normal daytime light conditions. These days it is possible to create fully retro-reflective material in a range of bright colours, such as those used in the Proviz CRS Plus Cycling Jacket. Whilst these jackets for cycling are not fluorescent, their bright colour schemes make you easier to spot in daylight hours, while the fully reflective fabric is perfect for night riding. 

What is the difference between reflective and retro-reflective material?

If you wore a white, light-coloured or shiny garment while out and about at night, a certain degree of light, would be reflected if you encountered a light source, such as car headlights or a torch beam. However, the light would be scattered in all directions, meaning less light is returned directly towards the light source. Retro-reflective materials are specially designed to reflect the majority of light back towards the source. Wearing retro-reflective kit could help a driver to see you three seconds sooner, giving them more time to react, slow down and pass you safely.

Diagram illustrating how reflective material works

How is retro-reflective fabric made?

Retro-reflective fabric is constructed using tiny glass beads that have a high refractive index, so that the material can reflect the source of light at wider-than-normal angles. To create the fabric used in retro-reflective tape and material for reflective garments, these tiny glass beads are embedded into PE/PET film using electrostatic suction, which ensures that they are distributed evenly. The beads are then coated with adhesive and heated to fix them in place. They are then plated with aluminium, treated with more adhesive and then applied to a backing fabric before the PE/PET film is removed.

When do I need electroluminescent or LED kit?

Both electroluminescent and LED kit enhances visibility by emitting light even when there is no external light to reflect back to its source. Add LED or electroluminescent elements to your kit if you know that you will be exercising in a busy area where you will benefit from the additional attention generated by light-up kit. It’s also useful in really rural areas where there is little in the way of street lights and there may be other road users who do not have their own lights to illuminate any reflectivity on your kit. The most eye-catching setting for lights is flash mode, so it's worth investing in kit that has at least one flash setting.

Things to consider when carrying your own light source

It is illegal to ride a bike after dark without front and rear lights and you may want to have them during the day too, as inclement weather or even low sunshine can make cyclists without lights hard to spot. There is no legal requirement for runners to run with their own light source after dark, but if you are venturing away from street lights you may find it useful to run with a head-torch or to add illuminated elements to your kit, such as trainer lights, an electroluminescent vest or arm lights. All of these accessories will help you stay visible to people who do not have a light source to illuminate retro-reflective elements on your kit and a head torch will help you see where you are going.

If you are shopping for bike lights or a head torch be aware of the angle and brightness of your light. The lumens rating on a light refers to the amount of light it emits and the lux rating is a measure of the intensity of illumination. Higher lux ratings indicate a narrower, more intense beam and the highest lux-rated lights may be counter-productive, dazzling on-coming traffic in the same way that undipped headlights on a car do. These high lux lights are great for off road adventures after dark but not advisable for commuting in high traffic areas.

Read more about finding the right bike lights in our Buyers Guide to Bike Lights

Proviz Nightrider Yellow Jacket UGC and Model Shot

What is the best daytime visibility cycling kit?

Cycling gear is a multi-billion pound industry and many cyclists are as keen to be at the forefront of fashion on their bike, as they are to break away from the peloton in a cycle race and cross the finish line first. Many cyclists are therefore reluctant to dress up like Christmas trees in order to be noticed by other road users, especially as much of the premium cycling gear in the press predominantly uses neutrals as its base colour.

However, it is possible to find daytime cycling kit that satisfies in terms of both style and safety. If you really don’t want to wear head-to-toe fluorescents, go for flashes of bright colour that are visible both from the front and from behind and choose accessories that are hi-vis, such as your backpack, backpack cover and cycle helmet. Opt for bike lights with have a broad range of settings that can easily be changed whilst you are on the go. That way, if visibility deteriorates during the day, you can maximise your visibility with brighter or flashing light settings.

UGC Daytime Running Visibility

What is the best daytime visibility running kit?

Fluorescent kit that clashes with your environment should be adequate for the majority of daytime runs, even in the depths of winter. If it is particularly foggy or the cloud is really low, incorporate some LED or electroluminescent kit to maximise your visibility. It’s important to remember that you share responsibility for your safety with others, so if weather conditions aren’t great, maybe leave the headphones at home to give yourself a few seconds more warning of approaching traffic.

REFLECT360 Gilet and Jackets under light source in the dark

What is the best nighttime visibility cycling kit?

If you are starting and finishing your journey in the dark and the majority of traffic you encounter will be cars, a retro-reflective jacket will make you far more visible to other road users. If part of your journey includes daytime riding, make sure you incorporate hi-vis in your kit choices too, as most reflective panels and detailing will appear a drab, pretty ignorable grey in natural light.

Proviz reflective running gear

What is the best nighttime visibility running kit?

If you are squeezing in your autumn and winter runs in the dark of the early morning or late evening, you really need kit that is both flourescent and retro-reflective. With the sky potentially lightening as you finish your morning run, a purely reflective garment will do little to enhance your visibility as the sun comes up. Conversely a bright yellow top will be inadequate for an evening run that finishes in full darkness and retro-reflective elements should be included in your kit too. Make yourself stand out even more by incorporating electroluminescent or LED elements to your kit, such as trainer lights or LED armbands. If you are venturing away from street lights and other external light sources you may want to consider wearing a headtorch, both to see where you are going and to allow others to spot you more quickly. 


Whilst safety during your runs and rides is really important, there are a lot of other factors to consider too. There is little point investing in the most highly visible kit if it is unflattering or uncomfortable and will put you off getting on the bike or lacing up your running shoes in the first place. Look out for breathable hi-vis jackets made of waterproof fabric with comfort-focused extras such as underarm vents, fleece-lined collars and adjustable cuffs, as these will remain comfortable even if you are on an intense fitness ride or run in bad weather. 

Few of us want to have a wardrobe heaving with a multitude of options of things to wear whilst exercising after dark, as it is neither cost effective nor environmentally friendly. Look for kit that multi tasks by incorporating fluorescents, retro-reflective elements and maybe even an LED flasher. Having said that, it is also worth remembering that as temperatures go down we will be layering up for our time outdoors. There is little sense in having a hi-vis vest if you then cover it up with a black jacket or a hi-vis jacket that you then strip off to reveal a black tshirt when your effort session ramps up. Ensure that all your layers are multi-tasking hi-vis, so that you don't get caught out.