Success Stories
Prapontin Tunnel (A32 motorway - Turin Bardonecchia) (Italy)

Luminous flux regulators for the Prapontin tunnel (A32 motorway - Turin Bardonecchia)


Since the beginning of the 2000s, SITAF has been implementing a program to adapt the lighting systems of the A32 tunnels to the increasing flow of traffic and to the regulations, balancing the safety and comfort of road users with the needs for energy saving, reaffirmed today. from the European directive 2005/32 / EC.

Up to now, this program has led to the restructuring of the Prapontin (2003) and Serre la Voute (2004) tunnel systems in compliance with the Ministerial Decree of 5 June 2001.

The new systems also comply with the most recent Ministerial Decree of 14 September 2005, even if this decree does not require it for tunnels renovated before its issue on the basis of the previous Ministerial Decree.
Below, the results obtained in the construction of the lighting system of the Prapontin Tunnel, approximately 4.5 km long.


In addition to the aforementioned standards and decrees, the SITAF client has imposed some additional design conditions as follows:

2.1 - maximum respect for ride comfort, in particular with reduced glare indices (TI threshold increase) and overall and longitudinal uniformity values ​​such as to ensure the absence of light and dark areas on the roadway;

2.2 - maximum guarantee of operation of the emergency circuits;
2.3 - reduction of installation costs also by minimizing the power supply circuits of the reinforcement system;
2.4 - minimization of energy consumption.

Point 2.1 led to the choice of a symmetrical system for both reinforcement and permanent lighting, also reducing the interdistances between luminaires below the design value in order to improve uniformity. To comply with point 2.2, the permanent lighting circuit has been divided into two parts, both powered by UPS. As regards point 2.3, luminous flux regulators with a wide adjustment range have been adopted, contributing to point 2.4 together with the choice of high pressure sodium vapor lamps and the evaluation of the veil luminance based on environmental measurements.

CIE 88 and UNI 11095 require that the illumination of the threshold and transition areas of the tunnel be correlated with the external veil luminance. Furthermore, in the event of discontinuous adjustment of the luminance level, luminance variations with ratios greater than 3 must be avoided. This rule obviously applies from the maximum level of street luminance up to the level of permanent lighting and in the transition from this to night lighting, in order to avoid on every occasion that the drivers of the motor vehicles are dazzled by excessive luminance coming from a less illuminated external environment, or they find themselves in the presence of a sudden lighting deficit while traveling through the tunnel due to an excessive partialization of the lighting system lighting.

Partialisation can be carried out for all or nothing by switching on or off parts of the system with ratios not exceeding 3 for street luminance or partially continuously using the luminous flux regulators in association with switching on and off.

In the field of the usual street luminances in the input section from 80 cd / m2 to 160 cd / m2, 4 levels are required if the regulators are not used, 3 with electromechanical and electronic regulators of normal conception, while the innovative phase cut regulators on the falling front they require only 2 jumps up to an input luminance of 243 cd / m2.

The adjustment of the entrance luminance is controlled by two luminance meters placed at the stop distance in front of the arches and connected to the luminous flux regulators.

These instruments will be replaced as soon as possible by luminance meters capable of measuring veil luminance, in order to improve the correlation with street luminance in the entrance and transition areas.

The system was built using Schréder type FV3 lighting fixtures with 83M Asim optics, equipped with super high-pressure sodium vapor lamps with powers ranging from 400 W to 150 W. The partialization of the system was made using Revetec luminous flux regulators and Intelux NG technology that guarantee partialization of up to 25% of the nominal luminous flux. The regulators are connected to the external luminance meters, which will soon be replaced by the Revetec SDL luminance meters capable of measuring the veil luminance, thus realizing with greater accuracy the correlation between the external veil luminances and the internal road and optimizing consumption. energetic.