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Optimum safety with Schréder LED tunnel solutions

A study has shown the superiority of Schréder LED tunnel luminaires sealed with flat glass over luminaires where the lenses are in direct contact with the atmosphere.

Optimum safety with Schréder LED tunnel solutions

Schréder LED tunnel lighting solutions provide optimum safety

A study has shown the superiority of Schréder LED tunnel luminaires sealed with flat glass over luminaires where the lenses are in direct contact with the atmosphere.

Carried out over three months in two separate tunnels, this study by Schréder's R-Tech laboratory based in Liege (Belgium) compared, under strictly similar conditions, two different approaches to LED lighting in this area:

  1. the approach used by Schréder, whereby luminaires are sealed with a flat glass protector and
  2. the more common approach, where the lenses are in direct contact with the atmosphere.

The purpose of the study was to quantify the impact of dirt on the photometry and the efficiency of both types of LED solutions.
To ensure that the results were objective, the luminaires were installed in three distinct areas but not electrically connected in order to eliminate any influence from any variation in the light source's inherent flux.
The performance of the luminaires was carefully measured in the laboratory prior to installation, at the end of the three month period and after cleaning.


After only 12 weeks in a tunnel, the study found that:

  • the reduction of the luminous flux was 10% higher when the lenses were directly exposed to the atmosphere compared to the solution with the glass protector

  • an unprotected luminaire loses 19% of its initial flux due to dirt, while the greatest loss in the case of a luminaire fitted with a glass protector is limited to 8%

  • after cleaning, the luminaires protected with flat glass recover 100% of their flux while the unprotected luminaires are permanently affected with a loss of 2.5% of the initial flux.

It is interesting to put these figures - recorded after only a few weeks of operation - into perspective with the lifespan of a lighting installation and the frequency of maintenance operations in a tunnel. Each maintenance operation irreversibly damages the unprotected lenses and reduces slowly but surely the general efficiency of this type of installation. 


Aggressive tunnel environments (exhaust fumes, soot, micro-particles etc) cause dirt to build up over time.
While dirt is deposited evenly on flat glass, forming a thin greasy film, it is deposited unevenly on the lenses, accumulating on the part that is exposed to the direction in which traffic is moving.
A dirty or damaged lens not only blocks the emission of light, it completely alters the general photometry of a luminaire and endangers the safety of users.

With dirty lenses, the distribution of light becomes asymmetric (pro-beam), which results in a significant loss of luminance (up to 42%).
However, with a Schréder flat glass solution, the change is no more than 15%.


The rapid deterioration in the performance of an LED solution using lenses in direct contact with the atmosphere directly or indirectly results in a number of major inconveniences:

  • a more substantial investment (the installation must be "over designed" to make allowance for the rapid reduction in flux);
  • users are put at risk;
  • higher energy consumption and
  • an installation with a reduced lifespan (irreversible damage due to cleaning).


Schréder’s LED tunnel lighting solutions with their unique technology provide the best solution through their:

  • energy efficiency
  • visual comfort
  • excellent colour rendering
  • superior safety by using a flat glass design which maintains performance over time.

Maintaining safety while reducing the need for maintenance is a major benefit for operators. Schréder understands this well and demonstrates on a daily basis the relevance of its technology with its LED tunnel solutions.




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