In tunnel lighting, as in other equipment, the buyer must be aware of unfulfilled promises and hidden problems. In the right situation LED luminaires have certainly been working well so far. It is early days, however, and some experts advise caution, chiefly on technical grounds. And there are, of course, alternatives. The excitement over LEDs has overshadowed the possibilities for induction luminaires. Another recent development with fewer sources, this type of lamp has a much longer life of up to 100,000 hours claimed for it and so running lower costs. Both induction and LED luminaires are currently more expensive in unit cost than the previous favourite of high-pressure sodium lamps and, of course, standard fluorescent tubes. Sodium lamps still have their proponents for long, fast highway tunnels, and fluorescent lights can still have an important role in pedestrian areas of underground stations.
Lights from the East
A major characteristic of the lighting market is the huge number of very similar LED luminaires being made available from many different manufacturers in Asia. These are chiefly located in China but also emanate from Korea, Taiwan, the Philippines, Thailand and other countries. These markets also have varying levels of supplier service support available.
On the manufacturing side, specialist LED makers will supply to luminaire manufacturers and lighting installation engineers. Some leading and more sophisticated lighting manufacturers cooperate closely with consulting engineers and architects to offer a full service from concept to commissioning. This applies not only to the West but also Asian countries. In China, in addition to ‘off-the-shelf’ and Internet suppliers, there are major businesses with many tunnel lighting installations on their record, and also advertising partnerships with some leading Western component manufacturers such as Osram in Germany and Cree in the US.
Western manufacturers are also intensifying R&D efforts into LED devices as well as other types of lighting. One result of this is a dramatic increase in the claimed luminaire lifespan of the new types of induction lighting; i.e. up to 100,000 hours.
Cree says that its ‘The Edge’ LED tunnel luminaires are designed for 100,000 hours to reduce maintenance requirements. Lamp replacement was becoming a problem for the city of Arezzo in Italy in its Crocina Tunnel, so the city searched for more economical options. By installing 21 of Cree’s ‘The Edge’ triple light bar luminaires it is claimed that Arezzo will see energy savings of 61 per cent as well as improved lighting. Cree has also supplied numerous tunnel installations in China.
Testing times
Faced with a marketing onslaught, many operators and their consultants have wisely sought independent verification before investing too much faith and money in new designs. In France, the AREA/APRR Autoroute operator and consultants EGIS Tunnels have conducted on LED lighting in the l’Epine tunnel on the A43 autoroute. The programme was designed to be completely independent of possible lobbying and ‘fashion effects’. A general conclusion of the tests was that LED luminaires could be an interesting alternative to the commonly used high-pressure sodium lights for tunnel base lighting. However, the authors say that, at the time of writing, LED technology remains new and still in progress and optimisation. They claim it presents a high complexity and enhanced risk in all project phases.
Even in China, words of caution have been issued in various blogs on the subject of LED lighting and the claimed excessive development for street lighting. Seemingly adding fuel to this the Chinese government’s Ministry of Finance Joint Development & Reform Commission with the Ministry of Science & Technology, recently announced subsidies for qualifying LED manufacturers to promote further development of LED street lighting with the objective of lowering unit prices.
Shandong Liaoyuan sales director Caixing Mao recently says that, as pilot projects of a few hundred luminaires have become popular among local authorities, orders are now into the tens of thousands of units, greatly heating up the market. He reports that his company’s orders were three times more than for the same period last year.
Independent reference
Designing an appropriate lighting scheme for underground use is no easy matter. Even if a decision is taken not to light a road tunnel due to infrequent use, drivers can find this very daunting and need to approach the tunnel with caution, even if only to allow time for eyes to adjust to the change in light.
Similar problems, known as the ‘black hole effect’ can occur if the level of tunnel lighting is not smoothly graduated between exterior conditions (time of day or weather) and the tunnel interior. Other undesirable conditions that must be avoided in the tunnel are glare and flicker, through inadequate luminaire positioning and frequency, and insufficient contrast that can make it difficult to notice potential obstructions in time. A driver distracted and confused by uneven lighting, or unsure of what is ahead, is not a safe driver.
Fortunately independent design guidance is available, particularly for highway tunnels, through the International Commission on Illumination (CIE) through its technical report 88, revised in 2004, titled ‘Guide for the Lighting of Road Tunnels & Underpasses’.
The basic concept is to split a tunnel (if of sufficient length) and its portal zones according to the required luminance. The transition curve between these levels of luminance should also be as smooth as possible. The lengths of the access and exit zones depend on the design stopping distance of vehicles using the tunnel.
Induction alternative
As mentioned previously, the alternative of induction discharge lamps has been somewhat overshadowed by the wide availability of LED lighting. Both are cheaper to run than the most common existing luminaire type of high-pressure sodium (HPS) discharge lamps. The Chinese manufacturer HongYuan of LVD induction lighting has issued case history data comparing the performance of both
HPS and LVD lighting due to renovation of the Yanlieshan North Tunnel. Using LVD induction lights having a life expectancy of 60,000 hours, the annual electricity cost saving achieved was 62.4 per cent, or CNY 1.078M (USD 170,880) even allowing for maintenance, compared to the previous HPS lighting. This was derived from a power saving of 1,221,954kWh per year. The induction lamps also give a whiter light compared to the more yellow sodium lighting, giving a better indication of true colours in the tunnel.
A small drawback of induction discharge lamps is that, like earlier discharge lamp designs, they incorporate mercury in their mechanism causing possible disposal problems. However, the amount is relatively small and with the greatly extended life of the lamps, the problem is minimised.
Control
There is more to tunnel lighting than installing some new lamps. How do you make sure they are all operating correctly throughout the day, for maximum safety and economy? For most busy traffic tunnels, physical inspection is out of the question due to operational disruption and cost, as well as opening operators to ridicule about ‘how many tunnel workers does it take to change a light bulb’. The answer is one of the recently developed intelligent control and monitoring systems.
Scanlight AT, produced by the combined work of P. Ducker Systems (PDS) and TRT Lighting includes Digital Addressable Lighting Interface (DALI) individual control and interrogation facilities on each luminaire. It allows the central control system to dim lighting to the minimum required for safe operation in the predetermined zones (see CIE guidelines) under the prevailing conditions (portal
luminance). It also permits each fixture to be interrogated to determine whether it requires maintenance attention or replacement. This avoids unnecessary inspections, which could disrupt normal tunnel operations.
Nyx Hemera Technologies’ leading product is the Tunnel Lighting Addressable Control System (TLACS). Its first application was the second phase of a control system for the Kallang-Paya Lebar Expressway tunnel in Singapore.
Wall role
The surfaces of a tunnel can play an important role in the distribution of light within the tunnel, perhaps saving on luminaires but perhaps more importantly the quality of the luminance. This subject is also covered in the CIE technical report guidance and in Australia has a standard, AS1158.5, that specifies surfaces should be perfectly diffusing.
Various materials have been used to promote the required reflectance including prefabricated panels, sprayed coatings, tiles and special concrete mixes. Apart from the purely functional aspect of reflective walls, the lighting design has sometimes become an integral part of underground space architecture, particularly for pedestrian use, so as to make the space more interesting and welcoming. This has even been the case in some transport tunnels. Concerns about the length of the Laerdal Tunnel in Norway, the longest road tunnel in the world, affecting the concentration of drivers led to research by SINTEF about ways of creating more interest to promote safety.
This resulted in the inclusion of several rock caverns along the route and colour lighting schemes.
Green to the end
The drive for sustainable or green lighting correlates with running costs savings that can now be achieved, but it doesn’t end there. Many countries have controls on the disposal of electronic and electrical goods, which encourages recycling. Any additional concern with some luminaires (but not LEDs) is that they include mercury, a well-known potential toxic pollutant that has to be disposed of with care.
Choosing suppliers
Clearly the factors involved in purchasing tunnel lighting are many, matched in numbers only by the possible sources of luminaires. These could even be purchased via the Internet from Asian manufacturers and trade websites. Established manufacturers in the ‘West’ such as Philips and Osram are said to be under pressure from the pricing and availability from the ‘East’, particular in LED lighting, but can fight back with their strong points of installation expertise and co-operation with a network of architects and specialist independent lighting engineers, plus general service support.
Indeed even some manufacturers and installers in China list western manufacturers such as Osram and Cree as partners. In between there are many lighting product distributors.
