Planes, trains and LEDs
Lighting systems in an increasing number of applications are being converted from conventional lighting to light-emitting diodes (LEDs), and the public transportation sector is no exception. The advantages are evident. Thanks to the long service life of LEDs, maintenance and lamp replacement are only rarely necessary, keeping the associated costs at a very low level for budget-conscious municipal or regional rail transit systems as well as airlines.
The flat dimensions of LEDs offer greater latitude in designing lumimares for small spaces and such long, narrow vehicles as subway cars, buses and airplanes, and these efficient light sources significantly reduce energy costs.
At the same time, particularly in the transportation sector, the demands imposed on lighting systems when switching from conventional to LED lighting have risen tremendously. A long service life, excellent light quality and homogeneous color rendering have become standard, as has very good service from the manufacturer.
One fundamental challenge in illuminating such transportation vehicles as trains or buses, is that the installed LED models must be available unchanged for up to eleven years, from the first design planning phase through to the next product revision cycle. In the rapidly growing LED market, with its continuous advancements and product innovations, just a handful of manufacturers offer this kind of long-term availability. What is more, longtime availability includes the properties of the LEDs, such as brightness, voltage, aging behavior, durability and color binning (grouping LED modules on the basis of light color and luminous efficiency).
Installing LEDs in transportation vehicles further requires absolutely uniform brightness. When individual defective lamps or LEDs are replaced, the brightness level must remain the same and should not increase uncontrollably. This goes against the widespread trend in the general lighting industry to continuously increase brightness, particularly in white LEDs. Meanwhile, different modes of local public transportation, as well as airplanes and railroad coaches impose their own unique demands on LEDs: While lighting systems must withstand constant vibration in road- and railway vehicles, the pressure difference between the cabin and the outer skin represents an additional challenge in aircraft use.
In general terms, the requirements for lighting systems in the transportation sector are a combination of specific characteristics from automotive and general lighting, and require a manufacturer familiar with both who has amassed know-how through decades of investment in research and development and adapted this to the transportation industry. The result is LEDs engineered specifically for transportation applications.
One innovation for buses and trains is the availability of a low-power LED that fulfills the core criteria for transportation lighting. A low price makes it particularly attractive to customers in price-sensitive markets, such as Asia and Eastern Europe. In contrast, higher-quality LEDs offer accent lighting in the low-power range.
There are many linear lighting applications to address, such as strip lighting on the side walls of buses and subways. great deal of the critical requirements in the transportation sector: There are mid-power LEDs available in various colors that have a long service life, high robustness, enabling them to withstand any number of environmental influences.
High-power LEDs are also available for spotlighting in transportation vehicles. These LEDs include infrared LEDs (IRED) for use in optical safety systems, such as in buses or cars. For example, the new Oslon black SFH 4716S with 1030 milliwatts (mW) optical power is one of the highest powered IREDs on the market. With a reflected beam angle of 150 degrees, the IRED illuminates a near-range of a few meters.
LED advantages: From cost savings to biological effect
In the price-conscious transportation industry, the greatest advantage of LEDs undoubtedly is their low service costs: Because of the long service life of the light-emitting diodes, they require only little maintenance and rarely need to be replaced. As a result, service costs are significantly lower than with conventional lighting systems. LEDs are the perfect solution for subway, bus, train and aircraft lighting thanks to their color and design variety. The look of an interior space can be changed by installing LEDs with different, correlated color temperatures: Long, narrow spaces, such as those common in public transportation vehicles, can be made to appear larger and more inviting. For design agencies, the unique color characteristics of LEDs offer an entirely new kind of creative freedom with the same materials, because the light color and color rendering index of LEDs can give surfaces a completely new look.
Considering the biological effect of light opens up entirely new prospects when it comes to designing lighting for long-distance flights or commuting by bus or subway to work, because light color and intensity have an effect on the human body and influence the body clock. Sufficient natural light, or cool-white light similar to daylight, is most important in the morning, but also during the day. It promotes concentration, as shown by a study conducted in 2012 at a school in Ulm, Germany, by Osram and the Transferzentrum für Neurowissenschaften und Lernen (ZNL – Transfer Center for Neurosciences and Learning). The study showed that people relax better in the evening under warm, reddish light. Biologically effective light can also help to mitigate jet lag, as found in a joint study by the University of Wuppertal, the Fraunhofer Institute for Building Physics IBP, Airbus, Diehl Aerospace and Osram.
Chronobiologically-adapted LED lighting in aircraft cabins, comprising warm light in the evening for a peaceful sleep and blue-rich cold light in the morning, can enhance a feeling of well-being overall and contribute to greater alertness on arrival.
Michael S. Godwin is the Director for Visible LED products for OSRAM Opto Semiconductors, Inc. In his role as Director, Godwin is responsible for product and marketing strategies for standard and custom LED products in the automotive, consumer, display and projection market segments in the NAFTA market. Prior to being named Director Godwin held the positions of Business Development Manager, General Marketing Manager and Product Marketing Manager. Godwin joined OSRAM Opto Semiconductors in 1999 and assisted in establishing marketing and application teams focused on the automotive industry. Through Godwin’s leadership, OSRAM was awarded as a finalist in the 2002 PACE Awards (Premier Automotive Commitment to Excellence) for white lighting on the Lincoln Navigator/Aviator. In addition OSRAM also secured the 2006 PACE Award for Color on Demand and most recently the 2011 PACE award for OSRAM OSTAR HL in forward lighting applications.