Seeing Clearly

While designing the Apidura Racing Series, we sought to better understand a key consideration for riders: visibility. Ultra-endurance riders spend long hours in the saddle out on the open roads – not just in race scenarios, but in the many hours of training rides that precede these events too. As a result, staying safely visible is of utmost importance.  For many races and audax, particularly in Europe, nighttime visibility is a legal requirement and there are specific standards required for visibility aids including Visibility Vests.

What makes something visible?

An object’s visibility is attributable to three key factors: colour, reflectivity, and form.

Colour

Across varying light conditions, the human eye is most sensitive to colours with a wavelength of about 550 nanometers, which is a fluorescent yellow-green. This is why many objects that need a high-visibility rating are a shade of green or yellow.  Legal visibility aids for night and poor visibility riding in Europe must meet the EN 17353 standard to be road legal. This standard, which was introduced in 2020, incorporates the older EN 1150 and EN 20471 standards sometimes referred to by event organizers. For events like Paris Brest Paris , this means the fluorescent element has been confirmed to be highly visible. 

Reflectivity

In scotopic (dim light) conditions, an object’s reflectivity becomes more important than its colour. When measuring the reflectivity of different colours (in candelas), it is apparent that fluorescent colours generally out-perform non-fluorescent colours quite comfortably. Fluorescent white (silver) is the most reflective, and it’s for this reason that it also features heavily in objects that require 24-hour visibility and fall under the EN17353 standard.

Form

Studies into the impact of shape and form on visibility show that a squared chequered pattern is the most conspicuous, due to its pattern and repetition. An object using colours that contrast with its background, and that uses reflective or high-visibility elements on its outer edges, will also help in increasing visibility. Moving objects, such as wheels (or pedals for a cyclist) are more conspicuous than static ones. 

Application

For riders to be as visible as possible on the roads, they should aim to exhibit colours that are highly visible around the clock, in all light conditions. For daylight hours, this means using fluorescent yellow and green. As the light begins to fade, riders should rely on reflective elements – ideally silver – to maintain visibility into darkness. 

Using highly visible, repetitive patterns in clothing items could also help in increasing visibility. Any hi-vis and reflective elements that help to define the size and shape of a cyclist will also help, so consider using reflective tape on the outer edges of things like wheels, handlebars and your helmet. Utilising the fact that moving objects are more visible, you can increase visibility yet further with additions such as fluorescent over-shoes (for spinning feet), or spoke reflectors (for rotating wheels).  

Nothing, however, is more visible than an object that is emitting light itself, so when it comes to being seen, more important than anything else is to ensure you have a good set of lights. To quote the TransAtlantic Way rulebook: “All riders need to light up like Christmas trees.”