How to light Highways

Ensuring the safety of all motorists

How to light Highways

Photometric requirements

The application of the CIE publication No.115-2010 which takes into consideration several parameters linked to the traffic and the road configuration, led us to classify a highway as being generally M3 or M4.
The values of the lighting criteria to respect are the following:

Class M3  Lave = 1.0cd/m²  Uo ³ 0.4  Ul ³ 0.6  TI £ 15%  SR ³ 0.5
Class M4  Lave = 0.75cd/m²  Uo ³ 0.4  Ul ³ 0.6   TI £ 15%  SR ³ 0.5

 

Light sources

LED luminaires constitute the best choice in terms of performance, energy savings, life span and colour rendering.
White light LEDs offer high visual comfort and a better colour contrast for improved driving conditions.
Their very long lifetime reduces the need for maintenance and when managed by smart control systems, they offer unlimited possibilities to adjust the luminous flux to the real traffic conditions.

LEDs provide higher performance photometries, suitable for both new and replacement projects and different installation layouts. Schréder designs its own lenses and with an efficient selection tool, we guarantee the best performance in all situations.

High-pressure sodium lamps provide a lower colour rendering, reducing the comfort when driving. Their control possibilities are very limited and they have a lifetime that is five times shorter than LEDs, thus requiring more maintenance.
Metal halide lamps provide white light but with an even shorter lifetime than high-pressure sodium lamps and lower energy performances.

 

Luminaires

The luminaires chosen to light highways should have a high level of tightness (at least IP 66), in order to maintain initial performances for as long as possible throughout the lifetime of the installation.
The resistance to mechanical impacts must correspond at the very least with the degree IK 08, in line the IEC standard 62262.

 

Installation layout

When the width of the central reservation between the two roads does not exceed 10m, the most appropriate installation layout consists of installing the lighting poles in the axis of this central reservation. Each pole will be fitted with 2 luminaires, one oriented towards each lane.
The height of the poles depends firstly on the total width of the roads together with the set-back of the luminaires from the border of the road. The luminaires are generally mounted at a height of 12m or higher.
When the central reservation is too wide (over 10m), a more efficient solution is obtained with two rows of poles in an opposite configuration, inside the central reservation or along the external borderline of each road.
 
The efficiency and the functional aspect of the lighting installation is of primary importance.
The aesthetic appearance can however be preserved by using well designed functional luminaires. A luminaire fitted with sources with a long lifetime (LEDs) is important to reduce the maintenance costs.

An accurate knowledge of the light reflection characteristics of the road surface is of primary importance to meet the above efficiency criterion. These characteristics can be measured by our exclusive system known as Memphis.
The following drawing shows a typical installation for a highway.

 

 

Smart lighting

 
The CIE 115-2010 enables the luminance levels to be adapted according to the traffic density but all other photometric requirements must remain the same if a dimming profile is used. The current possibilities of control systems enables the dimming profile to be pre-programmed or adapted depending on a real-time analysis of the traffic density.
The use of control systems is compliant with standards and can provide additional savings.

Example of a highway lighting installation

  

The Brussels ringroad is a highway section with 2 carriageways of 3 traffic lanes with a central lighting installation. The luminaires are mounted on 20m high poles with a spacing of 50m.
Teceo 2 luminaires were installed in 2013 to replace the old fixtures fitted with low-pressure sodium lamps.
The Teceo luminaires are equipped with 136 LEDs to provide the required lighting levels according to standards (1.5cd/m²) and will maintain the initial performance over time.
They have also been fitted with the Owlet remote management system which dims the luminaires to 3 different lighting levels during the night (70% - 50% - 70%) providing a 35% reduction in energy consumption compared to the old lighting scheme. 
This optimised lighting over a long life span will dramatically reduce maintenance operations and divide costs by 7, which is a major advantage given the busy traffic on this motorway.  

 

 

   

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