Standards / Road and Highway
EN 12899
Road and Highway
Current
Fixed Vertical Road Traffic Signs
EN 12899 is the European standard for fixed vertical road traffic signs, covering the sign face, the retroreflective material that makes it visible at night, the structural performance of the sign and its supports under wind, and the durability required of the whole assembly in service.
Scope
EN 12899 applies to permanently installed vertical road traffic signs, including sign plates, internally and externally illuminated signs, retroreflective sign faces, the posts and supports that carry them, and the fixings between them. It covers structural loading, visual performance and durability.
Exclusions & Related Standards
- Portable and temporary signs, cones, cylinders and deformable delineators fall under EN 13422.
- Warning lamps and beacons fall under EN 12352.
- Barriers that contain vehicles rather than inform drivers fall under EN 1317.
- Retroreflective material worn by people falls under EN ISO 20471.
Key Requirements & Marking
Signs are classified by the performance of their retroreflective face, by their structural resistance to wind loading and to dynamic snow loading where relevant, and by the deflection permitted in the sign and its support. The retroreflective class determines how much light the face returns to a driver at the angles that actually occur on the road, which is what governs the distance at which the sign can be read at night.
The retroreflective class governs the distance at which the face can be read under headlights.
Testing Overview
Assessment covers photometric measurement of the retroreflective face at defined observation and entrance angles, colorimetric measurement of the colours used, structural testing or calculation of the sign and support against wind and point loads, and durability assessment including weathering and resistance to corrosion.
Selection Guide
Select the retroreflective class for the road environment: higher classes are used where approach speeds are high, where the sign sits away from the driver line so the light strikes it obliquely, or where competing lighting reduces contrast. Confirm the support is specified for the wind loading at the location and for the sign area actually being mounted, which changes if a sign is later enlarged.
Inspection, Care and Maintenance
- Keep sign faces clean, since road spray and dirt reduce retroreflective performance far more than they reduce daytime appearance
- Check that the sign remains square to approaching traffic and has not been rotated by wind or impact
- Cut back vegetation that has grown into the sight line since installation
- Inspect posts and fixings for corrosion and for loosening, particularly on signs subject to buffeting from passing heavy vehicles
- Replace faces that have faded, delaminated or lost retroreflective performance rather than relying on daytime legibility
Dirt and rotation both remove night-time performance while the sign still looks correct by day.
Frequently asked questions
What does the retroreflective class of a sign control?
How much light the face returns to a driver at the angles that occur on the road, which governs the distance at which the sign can be read at night. Higher classes are used at higher speeds and where the sign sits off the driver line.
Why does a dirty sign matter more at night than by day?
Because dirt scatters the light that retroreflective material is supposed to return along the path it arrived on. The face can look acceptable in daylight while its night performance has largely gone.
Does the support need to be specified as carefully as the face?
Yes. The support is designed for the wind loading at the location and for the sign area being carried, so enlarging a sign on an existing post changes the loading it was designed for.
What is dynamic snow loading?
The load applied when snow is thrown against a sign by passing vehicles or a plough, which is a different and often larger load than snow simply settling on it.
How does vegetation affect a compliant sign?
It removes the sight line the sign depends on. A sign that met every requirement at installation can be entirely hidden by a season of growth without anything about the sign itself changing.