Hi Vi Vest Guide
Hi Visibility Explained
Hi Vis clothing is highly reflective and is manufactured using materials which conform to the hi vis standard ISO 20471. It must use reflective tape which meets the parameters specified in this standard.
In high visibility clothing, the leading retroreflective material is a product by 3M called Scotchlite. You can think of it as a material embedded with lots of very small cat's eyes.
Retroreflectivity is explained on the Scotchlite website as:
Retroreflective materials appear brightest to an observer located near the original light source, such as a car’s headlights. Since very little light is scattered when the light is returned, retroreflective materials enhance the contrast of the wearer for an observer located near the original light source.
Source: Scotchlite Reflective Material
Hi Vis Vests
Common uses are on and around roads, on building sites, in security situations and, of course, within the emergency services. Hi Vis garments that meet the ISO standard are made in hi vis yellow and hi vis orange for visibility in the daytime and use the correct amount of retroreflective material for hi visibility in low light conditions.
ISO 20471:2013 Standard
The summary of the ISO 20471:2013 standard from the ISO website is:
ISO 20471:2013 specifies requirements for high visibility clothing which is capable of visually signalling the user's presence. The high visibility clothing is intended to provide conspicuity of the wearer in any light condition when viewed by operators of vehicles or other mechanized equipment during daylight conditions and under illumination of headlights in the dark. Performance requirements are included for colour and retroreflection as well as for the minimum areas and for the placement of the materials in protective clothing.The standard specifies 3 classes of visibility, outlined in the summary of the standard
Three classes of garment are defined based on three different minimum areas of retroreflective, fluorescent and/or combined performance materials. Each of these classes will provide a different level of conspicuity, class 3 being the class that provides the highest degree of conspicuity against most backgrounds found in urban and rural situations in daylight and in night time. Users should select the required class of performance based on a risk assessment of the location/situation in which the protection afforded by clothing to this International Standard is required.
Class 3 - Highest Visibility Safety Level
Class 2 - Intermediate Visibility Safety Level
Class 1 - Lowest Visibility Safety Level
Which Visibility Class Vest Do I Need?
For working on or near high speed roads or other high risk environments you must choose Class 3 long sleeve garments.
If working on or near standard roads or medium risk environments then you'd need Class 2 at least.
For other jobs where a level of visibility is useful but not vital, then Class 1 is sufficient.