Standards / Road and Highway
EN 12352
Road and Highway
Current
Warning and Safety Light Devices
EN 12352 is the European standard for warning and safety light devices used in traffic control: the lamps, beacons and light units placed on temporary layouts to make them visible at night, in fog and in conditions where retroreflective devices alone are not enough. It classifies devices by their light output, their flash behaviour and their environmental durability.
Scope
EN 12352 applies to warning and safety light devices used with temporary and permanent traffic control equipment, including steady-burning and flashing lamps mounted on cones, barriers and signs, and units used to delineate a closure at night. It covers luminous intensity, flash rate, the angular distribution of the light, and resistance to weather, vibration and impact.
Exclusions & Related Standards
- The devices the lamps are mounted on fall under EN 13422.
- Fixed vertical signs and their retroreflective faces fall under EN 12899.
- Vehicle restraint systems fall under EN 1317.
- Area floodlighting of the works, as distinct from warning devices, is outside the scope.
Key Requirements & Marking
Devices are classified by luminous intensity, by whether they burn steadily or flash and at what rate, and by the angles over which the light is distributed. The distribution matters because a lamp bright directly ahead but weak off-axis disappears on a curve or on an approach that is not straight. Devices are also classified for environmental performance, since they spend their service life outdoors being vibrated by passing traffic.
A lamp bright only straight ahead disappears on a curved approach, so the angular distribution matters as much as the intensity.
Testing Overview
Assessment covers photometric measurement of luminous intensity across the declared angular range, verification of flash rate and duty cycle where applicable, and environmental testing including water ingress, temperature extremes, vibration and mechanical impact.
Selection Guide
Use steady lamps to define a line, since a row of them reads as an edge to follow, and reserve flashing devices for points of change such as the start of a taper. Select intensity for the ambient conditions: a device adequate on an unlit rural road can be lost against street lighting or against illuminated signage, and an over-bright device creates glare that makes the rest of the layout harder to read.
Inspection, Care and Maintenance
- Walk the run after dark to find failed units, since several dead lamps in sequence read as a gap in the line
- Check and replace batteries on a planned basis rather than waiting for units to fail
- Clean lenses, which fog, yellow and collect road film in service
- Keep dusk sensors unobstructed, as a covered sensor leaves the unit off all night
- Recover and account for units at take-down, as an abandoned flashing lamp continues to signal something that is no longer there
Several failed units in sequence read to a driver as a break in the closure line.
Frequently asked questions
Why are lamps needed when cones are already retroreflective?
Retroreflective devices depend on a driver headlight reaching them at a usable angle. In fog, heavy spray, on a curve or over a crest that often does not happen, and only a device emitting its own light is detectable.
What is the difference between steady and flashing devices?
A row of steady lamps reads as an edge to be followed. Flashing draws the eye to a point of change such as the start of a taper. Making everything flash removes the distinction.
Why does the angular distribution of the light matter?
Because a lamp that is bright directly ahead but weak off-axis disappears on a curve or on an approach that is not straight, which is exactly where the warning is most needed.
Can a warning lamp be too bright?
Yes. An over-bright device creates glare that reduces a driver ability to read the rest of the layout and to see anything outside the lit area, including people.
How should lamps be checked?
By walking the run after dark. Counting units from a vehicle does not find fogged lenses, flat batteries or covered dusk sensors, and several failed units in sequence read as a gap in the line.