Road lighting: the Palazzoli electrical system

Example of road lighting: illumination of a roundabout with junction lane (extra-urban street)

Road lighting requires attention, especially in terms of the safety of the categories of users involved.

The parameters in play are multiple and varied, in this article we will list the main ones:

• It is necessary to consider the coexistence of several types of users, for example: pedestrians and vehicles;
• It is necessary to make the visibility of the environment safe for all users, reducing the risk of accidents, this issue is even more important in road intersections, considered conflict zones and therefore at greater risk;
• Respect for the environment in terms of light pollution and energy saving, evaluating the upward emissions and efficiency of the sources over the ignition period.

Lighting standards for road lighting

UNI 11248: "Road lighting selection of lighting categories"

The standard defines the design methodologies for the type of road and the related lighting category of project, based on what is defined as "Risk Analysis". 

Appendix A provides indications to illuminate road intersections, in particular chapter A.3 contains information on how to set up a calculation for the illumination of roundabouts.

The standard also specifies some important indications on the design of "adaptive systems", that is, capable of guaranteeing high energy savings.

UNI EN13201: “Road lighting. In parts 2, 3 and 4.”

The standard, in part 2, provides indications regarding the lighting parameters to be respected based on the identification of the project category, such as:

• average luminance in cd/m2, where it is possible to position an observer (e.g. roads): Lm
• medium lighting in lux, where it is not possible to have a single observer (e.g. parking lots): Em
• general uniformity (min/med): Uo
• longitudinal uniformity (min/max): Ul
• glare: Ti
• surrounding lighting: REI

Electrical standards

64-8: Electrical installations with nominal voltage not exceeding 1000 V in alternating current and 1500 V in direct current

Particular specifications

Laws against light pollution, different from region to region.

THE CHOSEN SOLUTION

Applying what is stated by the rules above, it is possible to indicate some design ideas:

• carry out a correct risk analysis, based on the indications of the client and the characteristics of the environment. In the case of illuminated access roads it will be necessary to increase the project category of the roundabout of a class, as a conflict zone. On the other hand, if the roads are not illuminated, the project category of the road with the highest entry category can be maintained;
• provide the correct lighting for the unlit access branches for a length equal to at least the space covered in 3 seconds (in the case of 50 km/h we speak of about 40 m);
• choose the correct type of system between lighting tower or perimeter poles and verify that the equipment used has mounting accessories that allow easy installation on lighting towers;
• check the emission above the horizon of the devices, in order to comply with regional laws against light pollution, where applicable;
• correctly evaluate the efficiency of the devices in terms of lm/W and useful life, due to the fact that the system will remain on for a long time: the better the efficiency, the greater the energy saving; the longer the maintenance cycles will be;
• provide flow control systems in the hours of least use. In this regard, the latest version of the standard speaks of “adaptive lighting systems”.

CASE STUDY - THE PROJECT: LIGHTING A ROUNDABOUT

The project concerns the lighting of a typological roundabout connecting a main extra-urban road and the respective secondary road network.

Parking area: Headlight tower installation height: 20m;

Number of luminaires mounted on the lighting tower: 7

Average illumination: 25 lux;

Overall Uniformity: 0.44

The roundabout has a diameter of about 70 m and connects a main suburban road to two secondary roads.

As the main road was not illuminated, the risk analysis placed the area in the same lighting category as the main road.

Using the comparative table between luminances and illuminances (table 6 of the standard) we have:

Project category C2:

Average lighting required: 20 lux;

General uniformity required: 0.40

ROAD LIGHTING: ENERGY SUSTAINABILITY AND VISUAL COMFORT

The device chosen for the roundabout lighting of the environment described above belongs to the X-TIGUA family.

X-TIGUA is equipped with energy-efficient LED sources.

The characteristics of X-TIGUA:

• system power 336W;
• luminous flux 41,160 lm;
• efficiency: 122 lm/W;
• light intensity class: G6;
• color rendering CRI > 70.

Concentrating asymmetric optics allow to optimize the ratio between installation height and number of devices on the lighting tower.

ROAD LIGHTING WITH X-TIGUA: IMPROVING RELIABILITY

Why X-TIGUA makes it possible to increase reliability in the field of road lighting?

• uses the latest generation LEDs with a life of more than 100,000 hours with ambient temperatures at + 55°C.
• made of EN 44300 aluminum alloy with low copper content to withstand in highly aggressive environments;
• the bracket equipped with a goniometer allows the projector to be adjusted from -110° to + 110°;
• equipped with dimmable power supplies for flow control