Traffic Sign Design/Materials
The materials used for traffic sign faces have developed significantly of the last few decades, from humble beginnings using enamelled materials, through to reflective materials and recently microprismatic materials.
Current Sign Face Materials to EN 12899-1 2007
A sign face is a composite of a facing material and a substrate to support the facing material. The most recent standard is a European code with a National Annex outlining the use of the code in the UK. The code covers all aspects of sign face materials, including substrate materials, performance against wind and snow loads, life expectancy and resistance to dust and water ingress. Perhaps the most used part of the code is the reflective performance of the facing material. Retroreflective classes available are:
This would have previously been the Class 2 material to BS873 and would be used for signs where reflective performance is not as important as Class RA2.
This would have previously been the Higher Specification Class 1 material to BS873 and would be used for signs where reflective performance is important, for example for warning, prohibitory and direction signs. The retroreflectivity is based on glass bead technology and can be recognised by a cellular hexagonal or similar structure (about 5mm pitch) to the sign face material.
Current Microprismatic Sign Face Material to BS8408 2005
Known as High Intensity Product (HIP) or Diamond Grade Cubed (DG3). The material was introduced in the mid-1990s and is recognised by the diamond shaped prisms (about 6mm pitch) in the sign face material.
The product is used where standard glass bead based products wouldn't provide the level of performance required for the application, such as on high level gantries where headlights don't illuminate or where there is a high level of background illumination such as in a urban shopping street. The product is often incorrectly used in rural areas, where the high level of visual performance can be distractive to approaching drivers and thus counter-productive.
Although Microprismatic material exceeds some requirements of EN 12899-1:2007, it does not meet all of the code, thus a previous standard has been retained for application where the visual performance is important. Previous names include Visually Improved Product (VIP) and Long Distance Product (LDP).
Current Microprismatic Sign Face Material From 3M
New Microprismatic materials from 3M are designed to exceed the requirements on material performance in EN 12899-1:2007, but also provide a higher level of visual performance far in excess of that required by the code. Again, care needs to be taken not to specify Microprismatic when Class RA2 is appropriate.
Previous Sign Face Materials to BS 873
For many years, BS873 was used to define the performance of sign face materials:
Otherwise referred to as high intensity, this was the standard used for retroreflective warning, prohibitory and direction signs. It can be identified by a cellular appearance of hexagons or other similar type cell shapes.
Otherwise referred to as Engineer Grade, this was the highest standard for many years before the cellular type materials came to the market and then became a grade of material used for signs that required less importance to reflecting high levels of light back to the road user. Typically used in the 1990s for cyclist type signs and can be identified by the silvery speckle look to the material.
Although not defined in BS873, Class 3 became a term used for non reflective sign face material. Typically used for regulatory plates for waiting and loading restrictions and pedestrian signs.
|Traffic Sign Design|