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Calm interior lighting in an auto means a safe and stylish drive.
That also could mean the glaring lights inside cars that prevail today could go the way of the typewriter.
Taking cues from research in buildings and offices, today’s car designers started to incorporate gentle ambient interior lighting, which they feel could enhance night driving safety as well as increase the feel good factor about vehicle interiors, according to a new study.
Engineers based at BMW in Munich, Germany, led by Luca Caberletti, together with Christoph Schierz from the Lighting Engineering Group at Ilmenau University of Technology, also in Germany, decided to test different lighting set ups on drivers. The test took place in a driving simulation environment where 31 people “drove” a real stationary vehicle on a virtual highway with the driving environment projected onto three screens around the front and sides of the car. The light levels on the simulated street were between 0.1 cd/m² and 1.5 cd/m². The researchers tested twelve different lighting scenarios, with varying light color, luminance and position.
In the last decade the number of light sources in car interiors has drastically increased, up to a current maximum of 25 light emitting diodes (LEDs), although this is likely to rise further. Ambient lighting has become a staple of cars in the mid to high market ranges, and comes in a number of colors. Previous studies have shown the uncomfortable and distracting glare from interior lights, that can present driver safety issues, is eliminated when luminance is kept under 0.1 cd/m². Other studies show drivers are less distracted when they are in control of ambient lighting levels in the car.
In this study, drivers answered questions on space perception, perceived interior quality and attractiveness, perceived safety, functionality and alertness. Researchers also measured the drivers’ emotional states before and after the simulations, using a questionnaire.
The researchers found the driver’s whole perception of the car interior improved through the use of ambient lighting while driving. It intensifies space perception, enhances the perceived quality of materials and design, helps them find controls and with their orientation in the car, and makes them feel safer.
However, less is more when it comes to ambient lighting: A sprinkling of ambient lights can be just as effective as larger numbers in giving an impression of space and quality. In fact increasing the brightness does nothing to enhance impressions of the interior or help the driver, but rather leads to driver complaints of distraction from discomfort or glare. Drivers perceive blue lighting as brighter than orange or red, and color does seem to influence emotional responses. The researchers suggest color is important for “brand identity and design compliance”. Beyond this, the test did not come up with conclusive results for the effects of ambient lighting on the driver’s emotional state.
Ambient lighting did not influence the driver’s performance (although this was restricted to staying within a lane in this test). Research suggests further studies should look at more interior lighting colors, as well as a range of different car interior materials (because the effect of light on shiny leather is very different from matt fabric). They also want to further investigate the extent to which ambient lighting helps with secondary driving tasks, such as finding controls.
Another future direction is interior lighting that responds dynamically to inputs from the car, the environment and the passengers. “The advantages and problems arising from such systems, as well as their acceptance by the drivers, have still to be tested and verified,” Caberletti said. “Nevertheless, they offer a new, interesting, emotional and much more colored way of understanding and developing vehicle interior lighting.”

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