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General Motors Automobile Study

Evaluating Interior Lighting Schemes

General Motors Corporation (GM) asked the LRC to produce a lighting specification for automobile interiors. We responded to the request with four documents:

(Reading map in rear passenger seat.)
Man in Car
An Evaluation of Interior Lighting Schemes for Automobiles.
This document included a human factors evaluation of various lighting schemes for the major visual tasks in an automobile interior. We recruited subjects from the Clifton Park Senior Center to experience lighting mocked up in a Cadillac Seville STS and give us feedback on how well different lighting schemes worked.

A Specification for Interior Lighting.
The specification listed task illuminance, illuminance uniformity, luminance of the light source, illuminance at the driver's eye, and Color Rendering Index, and included guidelines for the seven major visual tasks performed in automobile interiors. (See specification table)

(Recommended locations for rear seat
reading light.)
Recommendations Measurement Protocols.
This document showed GM how to measure consistently the seven lighting performance characteristics in the specification so that measurements from different lighting vendors could be compared to the specification.

Best Practices.
What is the best way to light a map for easy reading? This section included general principles for enhancing visibility and reducing glare, as well as specific recommendations for optical systems and luminaire locations that would produce the best results.

What did we learn?

ChartThe amount of stray light at the driver's eye (from a map light, footwell light, or glove box light, for example) is an excellent predictor of whether the driver will find that light disturbing while driving at night. (Refer to chart: Percentage of participants who consider the lighting disturbing vs. vertical illuminance at the driver's eye--log plot.)

We also learned that auto manufacturers could make many simple optical changes that would dramatically improve both the performance and appearance of the interior lighting.

Rensselaer Polytechnic Institute
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