ROAD TUNNEL LIGHTING Lighting power controllers

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1 Lighting power controllers RNIG02E2 rev Via Artigianale Croce, Castelnovo ne Monti (RE) Tel Fax

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3 I N D E X 1. PREAMBLE 4 2. ROAD TUNNEL LIGHTING STANDARDS 4 3. THE TERMINOLOGY 4 4. THE FOCAL POINTS OF THE PROBLEM 4 5. THE VISUAL TASK 5 6. THE LIGHTING INSTALLATION AND POWER CONTROLLERS IN THE REINFORCEMENT ZONES 8 7. THE PERMANENT LIGHTING CIRCUITS THE EMERGENCY LIGHTING CIRCUITS CONCLUSIONS 12 APPENDIX A TERMINOLOGY 13 Power controllers rev. 2 Pag. 3 of 14

4 1. PREAMBLE The lighting of road tunnels is aimed at assuring traffic safety, a not easy task. The car drivers arrive from the external environment with a natural lighting level which can be very high, even over lx horizontally. Consequently, they look at a tunnel like at a black hole in which they are supposed to perceive the presence of dangerous situations, like obstacles, queues or traffic stops. Not to say about the luminance of the exterior environment around the tunnel opening (like the summer sky or the daylight reflected by the snow) which create a form of glaring which reduces the visibility. In order to minimise installation and energy costs for tunnel lighting, norms foresee to correlate road luminance with actual external lighting and traffic flow. These are conditions where the use of the regulators of luminous flux show very interesting aspects from the points of view of both the lighting applications and more generally of the economic implications. In the present document the problem of setting the lighting level in road tunnels is described with particular attention on both technologies of the regulators designed and manufactured by Reverberi Enetec srl, without any attempt to give a complete picture of their performances, which are described in the general catalogue of Reverberi Enetec srl. 2. ROAD TUNNEL LIGHTING STANDARDS After the known accident in the Mount Blanc tunnel, the Italian Ministry of Public Works issued a circular, published on Gazzetta Ufficiale of 18 September 2001, which requests the compliance with the publication CIE 88/90 Guide to the lighting of road tunnels and underpasses and foresees a tight updating programme for the existing lighting installations. The character of CIE 88/90, which was prepared and issued under urgent pressures, is mostly empirical and leads to conservative and expensive prescriptions, very often disregarded by road and highway administrators. Actually, both new and updated tunnel lighting installations complying with CIE 88/90 involve either investments and maintenance costs much higher than necessary. This is why CIE will soon publish an updated version of CIE 88/90 based on scientific foundations, which assures even higher safety levels in tunnels with less expensive prescriptions. Based on the same principles, UNI issued the norm Lighting of tunnels (2003), under acceptance by the Ministry of Infrastructures and Transportations, similar to the updated CIE 88 but for some luminance levels, which have no influence on the use of luminous flux regulators. 3. THE TERMINOLOGY The lighting terms used in the present document are defined at appendix A. 4. THE FOCAL POINTS OF THE PROBLEM The situation of road tunnels in Italy is clarified in the draft directive or the European Parliament 2002/0309 of the safety of traffic in the tunnels longer than 500 m existing in the Trans European Network (TEN), which includes only a minority of the Italian highways. Pag. 4 of 14 Power controllers rev. 2

5 Table 1 - Tunnels in the highways TEN, Trans European Network March 2002 Country Length > 1000 m > 500 m Austria Belgium 1 2 Demmark 1 3 Finland 0 5 France Germany Great Britain 6 12 Greece 3 45 Ireland 0 1 Luxemburg 0 3 The Netherlands 1 11 Portugal 1 2 Spain Sweden 0 3 UE minus Italy Italy Total UE Countries The number of TEN tunnels in Italy is almost equal to that of all the other UE countries together. Even if no analysis of the Italian road and highways tunnels is known, their number is estimated to be higher that Add to that that the Italian tunnels cross mountains, while in some flat countries there are only some underpasses and artificial tunnels and lighting does not involve big economic problems. Taking account of what said at point 2, it can be easily understood that in the next years the lighting installations of many tunnels will be updated according to the norm, not to say about the new tunnels as the ones foreseen in the new highway between Bologna and Florence. The consequence will be an increase of the requests of luminous flux regulators suitable for such types of installations. 5. THE VISUAL TASK Even if the aim of this document is not the lighting design, it is convenient to summarise the content of the norm for the sake of better understanding the advantages implied in the application of the luminous flux regulators in road tunnel lighting installations. Both CIE and UNI identify the safety conditions in the entrance zone of a tunnel with the visibility of a reference obstacle, actually a cube with 20 cm edges and diffusing faces with a reflection factor of 0,10: it is a very dark object, which is considered to represent the smallest potentially dangerous obstacle which could be found on our roads. Power controllers rev. 2 Pag. 5 of 14

6 In particular, if such type of object was present on the road in the entrance section of a tunnel, an accident could be avoided only if the driver could perceive it at the stopping distance from the said section, in order to permit to stop the vehicle in due time. As sown in figure 1, the actual stopping distance is much higher than what reported in the journals specialised in the automobile sector: actually, not only real tyres and roads are almost never in ideal conditions, but account should be taken of the reaction time of the average driver, which the norms assume equal to 1,5 seconds. 400 Stopping distance [m] Wet road Dry road Speed [km/h] Figure 1 Stopping distances versus speeds for horizontal roads Norms take account of what the driver sees from the stopping distance within a visual field of ±30 horizontally and ±20 vertically, as shown in figure 2 for a dry highway: it is without saying that the luminances in the visual field are completely different for the speeds of 70 km/h and 130 km/h. Figure 2 A tunnel seen from the stopping distances corresponding to the speeds of 130 km/h (left) and 70 km/h (right) The effect of the environmental luminance is the generation of a veiling luminance, which reduces the contrasts of an obstacle and consequently also its visibility. Pag. 6 of 14 Power controllers rev. 2

7 According to the norms, the road luminance that the lighting installation must generate at the tunnel entrance for making visible a possible (reference) obstacle is proportional to the veiling luminance, depending on the type of the lighting installation. For the sake of information and not of lighting design, table 2 reports some typical road luminances in the entrance threshold zone with maximum daylight level, dry asphalt and no snow as a function of the speed and of the visibility of the sky over the horizon and at the stopping distance from the tunnel opening. The big influence of the percentage of the visible sky and of the horizontal meteorological visibility is clearly evident. Speed [kmh] Table 2 - Typical threshold luminances Sky visibility over the horizon [%] Meteorological visibility distance [km] Entrance threshold luminance [cd/m 2 ] Road luminance diminishes along the tunnels because of the adaptation of the eye to darkness and reaches the minimum in the internal zone, where UNI prescribes for single and double way tunnels a luminance 1,5 or 2 times higher than what prescribed by UNI and CEN (table 3) for the access road. From the threshold luminance at the entrance to the interior zone the norms foresee a long transition zone, where the luminance decreases along a standardised curve shown in figure 3. The entrance threshold zone, where the luminance is at first constant and then decreases to 40% of the maximum at a distance from the tunnel opening equal to the stopping distance, is followed by an adaptation zone, whose length is evaluated in running time, since the eye needs always the same time to adapt to darkness independently of the actual speed: the length scale must be evaluated according to maximum speed, which in figure 3 is 130 km/h. Table 3 - Classes and luminances of the roads Road class Lighting Road Road category luminan. UNI CEN index [cd/m ] Highways A High speed roads D1 M1 6 2,0 Important traffic roads D2 Inter-block E1 M2 5 1,5 Block E2 M3 4 1,0 Local inter-zone M4 3 0,8 F Local M5 2 0,5 1 0,3 Power controllers rev. 2 Pag. 7 of 14

8 Entrance zone Transition zone Interior zone 100% Relative luminance 40% 10% Permanent lighting 1% Stopping distance 0 0 m Figure 3 Road luminances in the transition zone m 400 m 130 km/h 20 s 600 m 800 m In each zone of a tunnel the wall luminance must be at least the 60% of the road luminance in order to assure safety in a hostile environment. 6. THE LIGHTING INSTALLATION AND THE POWER CONTROLLERS IN THE REINFORCEMENT ZONE The lighting installation should be designed so as to realise the road luminance curve described in figure 3, where the relative luminance value 100% should be replaced by actual threshold luminance value at the entrance. Another characteristic to be complied with is the general uniformity U 0, evaluated dividing the average luminance between to subsequent luminaries by the maximum luminance in the same stretch, and the longitudinal uniformity U l, obtained dividing the minimum luminance along an axis of the stretch by the maximum luminance. The norms prescribe U 0 0,4 and U l 0,6. The lighting installation can be realised with symmetric luminaries, which emit light equally in both the running and the opposite direction, or with the so called counter beam luminaries, which emit light mainly against the running direction. In this second case the contrast of the reference obstacle is improved and a good visibility is obtained with road luminance lower than with the first method. However, the disability glare for the drivers is higher. The lighting installation should assure the required road luminance both with the maximum external sunlight in summertime and/or in winter with snow and sun. When the daylight level decreases during the day or the seasons, also the luminance generated by the installation must decrease proportionally. Traditionally, without regulators the decrease of the road luminance can be obtained switching out a number of luminaries and realising in this way a number of fixed luminance levels. The norm prescribe that the ratio between a luminance level and the immediately lower one should be not higher that 3. For example, in the case of a maximum luminance of 320 cd/m 2 like in table 1, the number of lighting levels which permit to reduce the luminance without exceeding the said ratio down to the interior zone luminance, here supposed to be 3-4 cd/m 2, is shown in figure 4: here the dimming requires 4 switching out levels and 4 electrical supply circuits, complete with all components. Like in figure 3, also here the logarithmic coordinates are used on the vertical axis: in this way, all the curves are equally distant vertically. Pag. 8 of 14 Power controllers rev. 2

9 320 cd/m cd/m 106 cd/m 2 Road luminance 10 cd/m 2 35 cd/m 2 12 cd/m 2 1/3 3,8 cd/m 2 4 cd/m 2 Permanent lighting 3 cd/m 2 0 Stopping distance s 130 km/h 0 m 200 m 400 m 600 m 800 m 1000 m Figure 4 Luminance levels with subsequent switching off without regulators If one continues to switch off luminaries, the distance between the ones still working increases and lighting on the road can be patch-wise and go under the minimum for general and/or longitudinal uniformity, with severe dangers for the traffic: to avoid these problems, in the installations without regulators the number of luminaries must be higher, with also higher installation and management costs. Vice versa, the Intelux regulators permit to reduce the luminance of each level to 20% before going to the lower one switching off some lamps: in figure 5 the field of actions of the regulators is hatched. 320 cd/m cd/m Road luminances 10 cd/m 2 67 cd/m 2 22 cd/m 2 1/3 8 cd/m 2 4 cd/m 2 Permanent lighting 3 cd/m 2 0 Stopping distance s 130 km/h 0 m 200 m 400 m 600 m 800 m 1000 m Figure 5 Luminance levels with regulators Power controllers rev. 2 Pag. 9 of 14

10 It can be easily be seen that the number of levels reduces from 4 to 2, together with the electrical supply circuits, with huge economic savings. Moreover, the risks to slip under the uniformity values of the norms are much lower, since between two subsequent levels a lower number of luminaries must be switched off. Looking at the problem from this point of view, the advantages of the Intelux regulators emerge clearly against the regulators with a dimming possibility limited to 50%, like the Reverberi models or in general regulators with transformers (Conchiglia, Irem, ES), which in the present case would require at least 3 reinforcement circuits. Furthermore, to the higher costs of cables and electrical components for supplying the higher number of supply circuits it is necessary to add a higher number of luminaries, equipped moreover with lower power lamps, with consequent higher costs not only for the installation but also for the energy management, since smaller lamps have lower luminous efficiency. Figure 6 shows a general picture of the lighting levels with and without regulators. It is to be noted that to reach 1 cd/m 2 from a starting maximum value of 350 cd/m 2 without regulators 5 levels are necessary, 4 using the Reverberi or transformer regulators and only 2 with the Intelux regulators, which permit to reduce the luminous flux to 20% of the nominal value Luminanze cd/m ,0 Senza regolatori Regolatori 50% - Reverberi Regolatori 20% - Intelux 2 1,0 1,3 1 1,3 1 1 Figure 6 Lighting levels of road tunnels with and without regulators: the progressive number of the lighting levels is reported within circles. 7. THE PERMANENT LIGHTING CIRCUIT As already said at point 5, the luminance of the road decreases along the tunnel since trough both the entrance and the transition zones the eye adapts itself to more and more low luminance, until the safety minimum in the interior zone is reached, where the norm UNI prescribes a luminance equal to 1,5 or 2 times the minimum prescribed for the access road by UNI and CEN (table 3) for single and double way tunnels. In the interior zone of the tunnel, lighting is assured by the permanent circuit, which is not limited to this zone but runs along the whole tunnel, with the aim of assuring the road luminance at the minimum safety value along the tunnel when the reinforcement circuits are switched off: by night, at sunrise and sunset, or by day with overcast skies. On the contrary, with external sunlight the specific role of the permanent circuit is to assure the road luminance in the interior zone (figures 4 and 5). Pag. 10 of 14 Power controllers rev. 2

11 But the luminance assured by the permanent circuit is not always the same. As reported at point 5, according to UNI the interior zone luminance should be at least 1,5 or 2 times the luminance prescribed by UNI for the access road (table 3), respectively for single or double way tunnels, provided that the traffic flow is at the maximum level foreseen for that type of road. When the traffic flow decreases at 50% and 25% of the said value, the lighting category index is declassified respectively by 1 and 2 units: in practice, in such conditions the road luminance decreases to about 75% and 50% of the value prescribed for that class of road, with considerable energy savings. Furthermore, according to UNI by night the road luminance in the whole tunnel should be equal at least 1 cd/m 2 or to the existing luminance on the access road if it is illuminated. However, the most restrictive condition for the permanent lighting installation follows from the uniformity prescription on road luminance, with a consequent inter-distance between the luminaries not higher than m, because of the necessity to assure the luminance uniformity with a height of the luminaries of no more than 5-6 m over the road. No problem on the contrary for the luminance levels, which with such inter-distances are assured through a low wattage high pressure sodium lamp in each luminaries. In order to realise the dimming of the permanent lighting installation at the above luminance levels, with the traditional systems every second luminaries should be switched off, but in this way it would be necessary to install the luminaries at an inter-distance of 5-6 m, so as to avoid that switching off every second luminaries the inter-distances of the dimmed installation climb to more than m, reducing the uniformity: figure 7 shows a schematic diagram of a typical permanent lighting installation realised with a single row of luminaries installed over the passing lane for a single way tunnel with two running lanes, but the situation would be similar with two rows of luminaries for a tunnel with three lanes. On the contrary, the use of the regulators with technology Intelux, but also Reverberi with some limitations, it is possible to dim the permanent installations with inter-distances of m. In this way, the number of both luminaries and supply circuits is halved, with huge economic savings for installation and management costs: actually, the lamps of an installation with inter-distances of m emit a luminous flux which is about two times the flux of the lamps with interdistances of 5-6 m, which adsorb more energy because of the lower luminous efficiency of the lamps with small power, even lower that 100 W, which are necessary in the last case. 10,00 10,00 5,00 5,00 5,00 5,00 With regulators Without regulators Figure 7 Typical case of a permanent lighting installation realised with and without regulators. Without regulators the number of both luminaries and circuits is doubled (higher installation costs) and it is necessary to use lamps with smaller power and consequently with lower luminous efficiency (higher energy costs) Power controllers rev. 2 Pag. 11 of 14

12 8. THE EMERGENCY LIGHTING CIRCUIT The norms foresee a emergency lighting installation, which, falling the electrical supply system, is supposed to generate in the whole tunnel a maintained average luminance of 1 cd/m 2, without any specific prescriptions for both general and longitudinal uniformities. In such conditions it is convenient to split the electrical supply of the permanent lighting in two circuits, base and emergency, supplying the latter one through an in line electronic continuity generator (UPS), as shown in figure 8: in this way the lack of the electrical supply system will reduce the road average maintained luminance of the whole tunnel to at most one half of the normal luminance in the interior zone and the regulator will further reduce the road luminance to the prescribed minimum level in order to save the energy supplied by the batteries, whose capacity can be reduced with reference to the same circuit realised without regulators. To be noted on this subject that the regulators with either the Reverberi technology and the Intelux technology can be cascaded with the continuity generators UPS: this means that it is not necessary to foresee any circuit instead of the regulators. Base circuit Emergency circuit 10,00 10,00 10,00 With regulators Figure 8 Emergency lighting with luminous flux regulators 9. CONCLUSIONS The use of the luminous flux regulators is extremely useful in the lighting installations for the road tunnels, since they permit to reduce the number of the electrical supply circuits and of the luminaries in both the reinforcement and the permanent lighting zones. In particular, the regulators with technology Intelux assure cost savings both for the installation and the management of the lighting much higher than with the regulators with technology Reverberi or anyway with the transformer regulators. Pag. 12 of 14 Power controllers rev. 2

13 APPENDIX A TERMINOLOGY TUNNEL LIGHTING TERMS AND DEFINITIONS Term Design speed [m/s] Stopping distance [m] Daily average traffic flow [vehicles/day] Hourly average traffic flow [vehicles/h] Access zone Reinforcement zone Entrance (threshold) zone Transition zone Interior zone Exit zone Immediately exterior zone Entrance luminance L e Transition luminance L t Interior luminance L i Definitions Speed adopted for the design of the tunnel or, if a legal limit exists, maximum permitted speed for assuring a safe driving through the tunnel. Stretch of road necessary for driving to a complete stop in safe conditions a vehicle which is running at the design speed. It includes both the distance covered during the reaction time and the braking space. Number of vehicles detected in the period of maximum traffic flow which cross a section of a lane during a number of whole days, more than one and lower/equal than one year, divided by the days Hourly traffic flow evaluated as the ratio between the daily average traffic and the duration of 16 hours/day when it is supposed that the highest daily number of vehicles is running. Stretch of open road immediately preceding the entrance portal of the tunnel, along which the driver should be able to see inside the tunnel. Stretch of tunnel where the lighting installation must be reinforced during the day with reference to the night; it includes the entrance and the transition zones. Stretch of the tunnel, whose length is equal to the stopping distance, along which the lighting must assure a luminance value such that to permit to the approaching driver to detect possible obstacles inside the tunnel from a distance equal to the stopping distance. Stretch of the tunnel, which follows the entrance zone, along which the luminance values are reduced gradually in order to allow to the driver s eyes to adapt themselves to the low luminance levels of the interior zone. Interior stretch of the tunnel which follows the transition zone, where the lighting installation is asked to generate constant luminance values such as to permit a safe driving in the tunnel. Ending stretch of the tunnel where, during the day, the visibility of a driver who is leaving the tunnel is influenced uniquely by the external light. Stretch of the open road immediately following the exit portal of the tunnel. Average luminance of the stretch of road corresponding to the entrance zone. Average value of the transversal luminance of the road at any point of the transition zone. Average luminance of the stretch of road in the interior zone of a tunnel. Power controllers rev. 2 Pag. 13 of 14

14 TERMS AND DEFINITIONS Term Exit luminance L u Equivalent veiling luminance L seq Atmospheric luminance L atm Windscreen luminance L par Veiling luminance L v Flicker General uniformity U 0 Longitudinal uniformity U l Threshold increment TI Definitions Average value of the transversal luminance of the road at any point of the exit zone. Luminance which veils the eye of a driver because of the diffusion within the eye of the perturbing luminances due to external luminous sources. Disturbing luminance of the vision due to the diffusion of the light in the atmospheric layers within the stopping distance. Disturbing luminance of the vision due to the light diffused by the windscreen of a vehicle. The sum of the disturbing luminances which from the stopping distance disturb the vision of the reference obstacle placed inside the tunnel. The disturbing phenomenon due to the periodical and quick appearance and disappearance of luminous sources, or of their reflections on the bodies of the vehicles, in the field of view of the drivers, due to an inappropriate distance between the luminaries. Ratio between the minimum and the average luminances calculated or measured on the considered surface. Ratio between the minimum and the maximum luminances calculated or measured along the axis of each lane. The measure of the disability glare produced by the presence of luminous sources within the field of view of the observer, defined as the percentage of luminance which should be added to the road luminance in conditions of threshold visibility, with reference to the luminance value which makes visible the same obstacle without the above mentioned sources, always in conditions of threshold visibility. Pag. 14 of 14 Power controllers rev. 2