EN ISO 20471: 2013 +A1: 2016
High visibility garments - Test methods and requirements 

The risks associated with movements on the roadway and the presence notably of construction equipment’s and road vehicles are important regardless of the weather conditions, day or night.

EN ISO 20471 is intended to facilitate the detection of people by wearing appropriate and efficient high visibility clothing.

Also, this standard specifies, among others, the requirements of materials, color, retroflexion, minimum surfaces of materials, and their positions on the protective clothing in order to achieve this goal.

3 classes are defined in terms of mandatory minimumvisible surfaces in m2.

Class 1  is the lowest and  Class 3 is the highest.

The classes of retroreflective materials of the old standard (EN471) has been cancelled and only the Class 2 is remaining.

In order to improve the detection of the wearer from all sides (360 °), all parts of the garment must contain fluorescent materials and reflective tapes, around the torso, around legs for the pants and sleeves for jackets (2 bands spaced by 50 mm).

Background fluorescent coloured material, for the day

Fluorescence is the ability of a material to reflect more light  than it receives.

Consequently fluorescent colors seem more vivid than those which does not have this property
Retro-reflective material for night
A retro-reflector is a device capable of reflecting the light it receives back in directions close to the source. Thus the driver who light a pedestrian in the night with the headlights of his vehicle, can identifies very quickly the garment which features a retro-reflective material.