Influence of LED Spectral Characteristics on Glare Recovery 2019-01-0845

Headlight glare is a major concern of the driving public. In the past couple of years there have been concerns expressed about the use of light emitting diode (LED) lighting technologies and possible impacts LEDs may have on people, including circadian disruption, retinal hazards, and glare. Under typical use cases, vehicle headlight exposures are insufficient to cause circadian disruption or retinal damage, but can result in disability and discomfort glare, as well as glare recovery. In general, white LEDs used for illumination have greater short-wavelength content than halogen lamps used in many headlights, and short wavelengths have been implicated in visual discomfort from bright lights at night. Previous literature is inconsistent regarding whether the spectral (color) content of a glare source affects the amount of recovery time needed to see objects, following exposure to a bright light such as a vehicle headlight. Warm and cool white LEDs were used as glare sources in the present study. They were energized and exposed to study participants at one of two illuminances (low, high) for either 3 or 6 seconds, after which participants were asked to identify the orientation of a Landolt ring target located on a display screen behind the glare source. Identification times were unaffected by the spectral content of the LED, but were correlated with the "dosage" of light from the glare sources, defined as the product of illuminance and duration. Although cool white LEDs will tend to be judged as creating more discomfort than warm white LEDs, they do not result in longer glare recovery times under the range of conditions used in this study.