How to choose optimum optical parameters?

What is light pollution?

Light pollution is excessive, misdirected, or obtrusive artificial light. Over-illumination, as one form of light pollution, occurs in traffic. Over-illumination means the excessive use of light. It happens mostly due to the incorrect choice and design of LED fixtures in traffic signs. This is the result of not directing light only to the areas needed, but letting light dissipate and, thus, not providing optimal light pattern.

Light pollution by Dynamic Message Signs can be caused by:
   • too high intensity
   • non-optimal light pattern
   • too wide B (beam width)

Consequences of light pollution are numerous, but the most critical are waste of energy and disruption of eco-system.

Traditional Variable Message Signs waste a large portion of light projected toward the road because they have symmetrically shaped beam of light.

Well-designed optical system shapes the light in such a way that it's projected exactly to the road with no light is wasted.

Safe choice of optical parameters

Beam width (cone of vision):
The satisfying cone of vision on most highways, arterial and similar multi-lane roads, is defined by class B6 or NEMA class e. It assures legibility of the sign mounted over the lanes and on shoulders.

 Luminance and Luminance Ratio:
Taking into consideration variance in drivers' vision, and unfavorable environmental conditions, the safe choice may be to select classes L3 and R3 (see tables above).
Selecting the correct parameters for a given application has a direct impact on VMS energy consumption. Insisting on cone of vision that is too wide adds to the operation costs, wastes energy and creates light pollution.



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