LED tunnel lighting applications rise what technical challenges?

The main purpose of the tunnel lighting is generally through the maximum visibility of an object provides a tunnel on the road, to prevent accidents, and enhance safety and comfort for the driver to pass into or through the tunnel.

Provides a guideline for CIE 88- "highway tunnel and underground channel Lighting Guide for tunnel lighting, is the foundation of many national regulations. According to the specific requirements of each of the tunnel will be divided into different regions.

First of all, the entrance to the very high brightness value, so that the driver's eyes can adapt to the lighting conditions of dark tunnel. The entrance length is determined by the maximum speed limit in the tunnel entrance section, because the higher the speed limit for longer.

Secondly, in the transition period, the brightness on the road slowly decreases until it reaches the level inside the tunnel lighting area, so as to provide meet at the entrance to the middle section of smooth. In the entrance section of the first part, consider the maintenance factor is 0.67, the lighting is about 150-300 cd/m2, and 2-6 cd/m2 in the inner region is usually limited.

The quality parameters of road tunnel lighting recognized include: overall uniformity of road surface and vertical illumination (ideally no strobe), tunnel wall lighting, avoid glare, color temperature and color rendering index. In recent years, the development of semiconductor technology, LED has gradually replaced the traditional tunnel lamp. Many national standards will be the requirements of the above parameters were updated.

The new custom LED standard

For example, in addition to the Swiss ASTRA (Bundesamtf u rStra? EN) outside the proposed regulations, Austria ASFINAG Planning Manual (PLaPB 800.562) is the first specifically for LED tunnel lighting system of. This standard will clusters into different categories of tunnel lighting, not only a detailed description of the different lighting requirements of each cluster, but also set out from 18 meters (cluster standard) to different distance between continuous lighting lamps. But it also on energy efficiency, lighting color and color for different requirements. Although the color in the tunnel lighting does not seem to be the most important index, but given the number of different color signals in road tunnels are increasing, for drivers, to quickly distinguish between yellow and red, or blue and green is very important.

Moreover, compared with the traditional lighting systems, the advantages of the LED system is also reflected in the real color lighting, high luminous efficiency and efficient distribution of lens. The LED system can provide analog dimming in inside the tunnel and the entrance area, thus eliminating the closed surface brightness caused by the whole group lighting uniformity. LED tunnel system currently has become intelligent solutions, can communicate with the driver of the current state of the lamp. However, on the support and control of electronic equipment where integration is still in the discussion. Some of the tunnels require the installation of intelligent driving lamps in the market, while others require that all electronic equipment installed in the tunnel or at the entrance of the internal control of building maintenance. These two solutions have advantages, which reduces the maintenance work.

Basically, in Germany, Austria and Switzerland, tunnel lighting the general characteristics and from the transformation of CRI 20-30 CRI 70 or 80 sodium, 4000 - 4500 K LED, and even some of the projects need to function even more than 110 lm/W, the system life of more than 80000 hours (during which the failure rate of less than 10%) of the system.

Figure 1: brightness adaptation curve tunnel

The lamp specification requirements outside

But some of the requirements, although very important, rely on the lighting equipment can not meet the. Especially early than the traditional LED lighting lamps more dazzling, so avoid glare becomes more and more important.

Some provisions have been required threshold increment to 8% or even 6%, because the threshold increment low means less glare. The threshold increment is relative brightness and surface brightness, surface brightness is lower or higher brightness can reduce glare. The flux itself depends on the brightness of lights and light distribution.

The manufacturer can be developed to maximize the road lamp brightness, but also can provide a relatively low brightness, but there is one of the key factors is unable to control. This is the Q0 brightness coefficient of pavement, it determines the relationship between illuminance and luminance of [cd/m2] [lx]. According to the road level, usually in 0.05 and change the brightness coefficient between 0.07. So, Q0 can change the brightness value of about 30% on the road. In turn, luminous flux lamps must be increased by 30%, which will lead to higher brightness and higher threshold increment.

Figure 2: tunnel lighting cluster comfortable

Figure 3: tunnel lighting cluster continuous

How to realize the function requirements and

A meaningful, but can not achieve the expected results of the requirements is the luminous efficiency, namely LM / W. This value perfectly describes the efficiency of LED, the luminous efficiency represents higher and higher energy efficiency. For all symmetric tunnel lighting light distribution, so it is generally applicable to this area, inside the tunnel. Because the market of different optical system transmittance value almost, nearly 90%, and the light distribution also provides similar surface brightness, so the luminous efficiency is to determine the best choice of the lighting energy efficiency. However, the entrance and the transition zone of the lamp?

Usually, these lamps will be equipped with the reflecting element can be very light to reflect the level angle to the driver.

Compared with the symmetric light distribution of the lamp, the lamp reflector provides better brightness value. Therefore, reflective lamp has been the entrance to the tunnel area selection in the past, both economical and efficient. However, these lamps