Tünel aydınlatması

Abstract

Bu tezin amacı, tünel aydınlatması ile ilgili konuları toplu bir şekilde sunmak ve hazırlanacak bir tünel aydınlatması projesinde izlenecek yolu basit bir bilgisayar programı örneğiyle ortaya koymaktadır. Bu kapsamda tezde öncelikle tünel aydınlatması ile ilgili temel kavramlara ve özelliklere yer verilmiş olup, tünel aydınlatmasının kalitesini belirleyen büyüklükler tanıtılmıştır. Daha sonra tünelde kullanılabilecek ışık kaynaklan ve armatürlerin özelliklerinden bahsedilerek bunlardan örnekler sunulmuştur. Tezin dördüncü bölümünde tüneller aydınlatma açısından incelenerek sınıflandırılmış ve ekonomik bir çözümle adaptasyonun sağlanması için tünel içerisinde farklı parıltılı bölgeler tanımlanmıştır. Beşinci bölümde ise eşik, geçiş, iç ve çıkış bölgeleri olarak adlandırılan bu bölgelerde sağlanması gereken parıltı seviyeleri Uluslararası Aydınlatma Komisyonu' nun (CIE) 88/1990 saydı raporu esas alınarak incelenmeye çalışılmıştır. Tünel aydınlatması hesabının bilgisayar destekli olarak yapılmasına imkan sağlamak üzere bu çalışmanın bir parçası olarak basit bir program da hazırlanmış olup, tezin altıncı bölümünde bunun ana hatlarıyla tanıtımı yapılmaktadır. Hazırlanan bu programda tünel bölgelerinde sağlanması gereken parıltı seviyeleri söz konusu tünelin parametrelerine göre belirlenmekte ve seçilen armatür tipi ile aydınlatma düzenine göre de tünel bölgelerinin ortalama parıltıları hesap edilmektedir. Tasarlanan aydınlatma düzeni ile, sağlanması gereken parıltı seviyelerine ulaşılamaması halinde ise armatür sıralan ve armatürler arası mesafe değiştirilmek suretiyle aranan parıltı seviyelerinin elde edildiği ideal aydınlatma düzenine erişilebilmektedir.

The purpose of this thesis, namely "Tunnel Lighting", is to present totally the subjects and principles related with the tunnel lighting and to show the way followed in a tunnel lighting project, with the help of a simple computer program. As we know, in a large number of countries tunnels form an indispensable link in the economic and social infrastructure. Wherever natural obstacles such as mountains and rivers occur, tunnels are essential for a rapid and smooth flow of traffic. This necessitates the studies on good tunnel lighting because optimum safety can only be guaranteed when tunnels are equipped with the best possible lighting systems. The aim of tunnel lighting is to ensure that traffic, both during day and nightime, can pass through a tunnel at a desired speed, with a degree of safety and comfort not less than that along the adjacent stretches of open road. In order to provide safe passing through tunnel it is necessary for a driver to see the objects which can be dangerous in the tunnel, at least, at the stopping distance. It is impossible for a driver closing to dark tunnel from an open and which has a very high luminance, especially in a sunny day, to have an appropriate visual ability because of the dark adaptation. Of course the ideal case is to light the first zone of the tunnel at the same level with the outside. But it is not considered because of the installation and management cost. Since the cost of the energy which were in fact very high, increased during last years, tunnel lighting should be realized at the minimum level which is necessary for a true visual ability. Luminance levels which should be ensured in the tunnel zones were largely explained in the thesis. In the second section of the thesis, basic concepts were placed in order to have a better understanding of the subjects related with tunnel lighting. In this context concepts of "luminous flux", "luminous intensity", "illuminance", "luminance" were explained in short. Besides, in this section physiological-optical principles such as "adaptation", "contrast detection", "visual acuity", "uniformity", "flicker" and "glare" which are important in tunnel lighting were examined. The photometric characteristics should be noted in the calculation of tunnel lighting. In this matter International Commission on Illumination (CBE)'s recommendations are very important. In order to ensure the visibility and the comfort for the driver good uniformity of luminance should be provided on the road surface and on the walls up to a height of 2 m. Two important uniformity for tunnel lighting are: vu 1-Overall uniformity 2-Longitudinal uniformity An overall luminance ratio (Lmin/Uv) of greater than 0,4 is recommended for the road and for the walls up to a height of 2m. The longitudinal luminance ratio along the centre of each traffic lane (Lmn/Lmax) should be greater than 0,6; but extremely high uniformities over long distances are not advisable, since they can cause fatigue for the driver and loss of contrast. Glare is also an important problem which should be avoided. The glare measure is named the threshold increment, T.I. This should be less then 15 per cent for all zones, with the exception of the exit zone during daylight. The T.I. value will be calculated by following formula: T.I. = (65. La) /(0,8. L^) for L^ < 5 cd/m2 T.I. = (95 Xa) / (1,05.Lort) for L,^ 5 cd/m2 With Lort= average luminance of pavement and walls forming the background La= veiling luminance created by all luminaires in the field of view up to 20° above the horizontal Another subject that should be taken into account in the calculation for tunnel lighting, is flicker effect. Flicker sensations are seen when driving through spatially periodic changes in luminance, such as those produced by louvered tunnel walls or improperly spaced luminaires. In general, the flicker effect is negligible at frequencies below 2,5 Hz. and above 15 Hz. Luminaires and lambs suitable for tunnel lighting are examined in the third section. An important factor influencing the total efficiency of a tunnel lighting installation is, of course, the type of light source employed. Following characteristics are expected in the light sources used in the tunnel lighting. 1-High efficacy 2-Long life Glare problem and the flicker effect should also be taken into account in the selection of lamps. Fluorescent lamps and low-pressure sodium lamps can be comfortably employed in the tunnel lighting because the longitudinal system is very appopriate for avoidance from the flicker effect. Fluorescent lamps' efficacy is appoximately 80 lm/w. Besides the low-pressure sodium lamp, the source with the highest luminous efficacy, has nowadays with the highly economic efficacy, SOX-E lamps up to 200 lm/w. It is recommended to use the fluorescent lamps for all lighting system through the tunnel moreover low-pressure sodium lamps which have high vui- efficacy should be added in threshold and transition zones. It is suitable for those lamps to be used with luminaires having asymetric wide beam. In the fourth section, classification of tunnels was made according to their lighting. In order to provide appropriate lighting, tunnels are classified as "long" or "short". Tunnel lighting is examined by dividing zones which have different luminance levels in order to provide the adaptation of eye and economic solutions. These zones (i.e. access, threshold, transition, interior and exit zones) are also introduced in this section. In the fifth section, the basic principles of calculation of tunnel lighting were given in detail. Within that context lighting system, contrast and luminance levels which should be ensured in the tunnel zones were examined especially in line with CIE' s recommendations. Luminance level which should be ensured inside tunnel depends largely on the contrast value. The higher an object's luminance contrast, the better its visibility. A lighting system which produces high road surface luminances, L, and low vertical illuminances, EV, (i.e., high values of the ratio L/Ev) gives relatively high contrast values for most objects on the road. Such a system will only be obtained when the lighting distribution is longitudinally asymmetrical and preferentially directed towards the drivers. This system is called "Counter Beam Lighting System". This system is more economic than symmetrical lighting system because it needs less (approximately 25 per cent) luminance levels. Determination of luminance levels in the tunnel zones which was explained in the fifth section can be summarized like that; 1) Luminance in the access zone: The adaptation luminance experienced in the access zone for an observer situated at the stopping distance from the tunnel entrance is the average of the luminances contained in a conical field of view of 2x10 degrees centred in the tunnel opening at a quarter of its height. This luminance is called the access zone luminance, L2o. Where reliable luminance measurements are not available (as, for example, in the case of a tunnel under construction), L2o can be read from the table prepared by CIE (Table 5-2 in this thesis) or derived from the table again prepared by CIE (Tabla 5.3 in this thesis) using the formula: L20= y.Lgök+ P-L yol + 8.L çevre where y, p and 8 each give the percentage of the 20 degree field of view occupied by the area concerned. In practice the highest occuring access zone luminance varies, according to tunnel type and measures taken, between approximately 3000 cd/m2 and more than 8000 cd/m2. 2) Luminance in the threshold zone: The relatively high luminance needed at the beginnig of the threshold zone to maintain the visual performance of the road user at a safe level is a function of L2o, the access zone luminance. The threshold luminance, L&, needed can be determined from the Lth/L2o ratios given in Table 1. for different stopping distances and for two types of lighting system. -IX- Tablo 1. Recommended Threshold/Access Zone Luminance Ratios 3) Luminance in the transition zone: A driver entering a long tunnel needs some time for his eyes to adapt to the lower luminance that will be experienced in the interior zone. The transition from the highest to the lowest luminances present must therefore bemade gradually, and this is the purpose of the lighting in the transition zone. The recommended reduction in transmission zone luminance, L^ along the tunnel axis is expressed by the formula: Ltr=U(l,9 + t)-1'4 where L& =thereshold zone luminance t=time(s) 4) Luminance in the interior zone: In the interior zone, adaptation is not necessarily complete and it is necessary to arrange for a level of luminance that is fairly high compared with the level needed on an open road at night. But the main reason for the higher luminance (apart from the feeling of increased safety that it engenders in the mind of a driver) is that visibility in the interior zone is likely to be reduced by the effects of pollution, which is why the luminance recommended is given in terms of traffic density and stopping distance (Tablo 2). Tablo 2. Recommended Interior Zone Luminances (cd/m2) 5) Luminance in the exit zone: Visual adaptation to increments in ambient light level is rapid and, therefore, extra lighting is not needed at tunnel exits for this purpose. Nevertheless additional lighting in the exit zone can be useful. Such extra lighting may be installed over the last 60 m of the tunnel at a level equal to five times the level of that in the interior zone. x- In this section, subjects of daylight variation and lighting control, nightime lighting, emergency lighting and maintenance will be introduced. In the 6th section, a presentation of computer program which is prepared according to the principles and data so far introduced, and which can be used in tunnel lighting, is placed. In this prepared program; provision of required luminance levels for tunnel zones is determined according to parameters of tunnels, and the luminances of tunnel zones are computed in terms of luminaire types and lighting system. Where the provision of required luminance levels could not be obtained with this designed lighting system the ideal lighting system which provides necessary luminance level can be obtained by means of changing the distance between luminaires and arrays of luminaires. Thus, first of all the quantities of tunnel lenght, height, allowed speed in the tunnel and road gradient are determined. Then, in relation to these prameters, calculations of stopping distance adaptation distance, lenght of tunnel zones and required luminance levels in these zones are made. After that the calculation of luminance in tunnel zones of prefered lighting system whose desing is determined according to its dimensions, is made. This is a very complex calculation. For every zone of tunnel a middle point is determined and contribution of all luminaires of the zone to this point is defined in terms of C and y angles. Besides indirect luminance effect is taken into consideration. So luminance value calculated for one point gives an idea about average luminance for this zone of tunnel. It is expected from an ideal tunnel lighting program to make a lot of point's luminance calculation in every zone of tunnel. According to that uniformity of luminance should be controlled. But this is a very complex work and exceeds the dimensions of a graduate thesis. Therefore very complex calculations are not included to this program which is avant-garda in a field where there is not yet enough studies. But required luminance level in the tunnel zones and the values obtained by prefered lighting system can be calculated by a relatively simple method with maximum accuracy. These obtained values can be compared and can be approximated to each other's level by changing the distance between luminaires and luminaires arrays. So lightings of tunnels can be provided at a most economic way and minimum level which does not damage the visibility.