Feasibility and acute alerting effects of a daylight-supplementing in-vehicle lighting system – Results from two randomised controlled field studies during dawn and dusk

Abstract

The present studies examined the feasibility and acute alerting effects of additional in-vehicle lighting within a passenger car. These factors were examined during morning driving (Study 1) and evening driving (Study 2). In a balanced within-subjects design, 37 participants drove a test car two times in the morning or in the evening. The test vehicle was equipped with either a daylight-supplementing interior lighting system or a placebo system, which participants were told would refresh the air. Both studies used identical protocols, and participants participated either in Study 1 ( n = 18) or Study 2 ( n = 19). In both studies, corneal illuminance levels were recorded while driving. Feasibility of the systems was assessed using subjective ratings. Efficacy outcomes were spindle rates in the alpha bandwidth of electroencephalogram recordings, performance on a psychomotor vigilance task and subjective sleepiness ratings. In both studies, daylight-supplementing significantly increased corneal illuminances while driving and did not cause any negative visual side-effects. Study 1 revealed lower spindle rates while driving under daylight-supplementing lighting, indicating that drivers had higher physiological alertness when exposed to additional light in the morning. This alerting effect of daylight-supplementing lighting, however, was not observed in Study 2. In both studies, performance on the psychomotor vigilance task as well as subjective sleepiness ratings did not significantly differ between the experimental conditions. The present studies provide novel evidence for the feasibility and positive impact of daylight-supplementing in-vehicle lighting systems on the physiological alertness of drivers under naturalistic driving conditions. Further studies are warranted to evaluate carry-over effects of increased alertness on road safety measures.

User Responses to Dynamic Light in Automobiles With EEG and Self-Assessments

“…Sensations generated from the living space are similarly applicable in the vehicle context. Researchers have explicitly explored controlling attributes of in-vehicle ambient light such as animations [36], brightness [14], color [12], and distribution [13]. orange-enriched white lighting, often labeled as warm white light, created a luxurious atmosphere in the vehicle regarding the influence of color and brightness of the illuminants within the vehicle environment [13].…”

“…In contrast, blue-enriched white lighting, frequently labeled as cool white light, more effectively influences drivers' awakening state [12]. Another study indicated that variation of brightness of blue-enriched white light controlled humans' physiological status, including alertness [14].…”

“…Previous studies facilitated physiological measurements to measure users' alertness and relaxation under ambient lighting. The physiological measurements involve the following: the electroencephalogram [14,23], electrocardiogram (ECG) [16], galvanic skin response (GSR) [7], or melatonin secretion [17]. A measurement type selection is made regarding the research objectives as each method has particular constraints or tolerances [27,18].…”

“…Previous studies have explored the effect of diverse light contexts on cognitive behavior [34,46,52], the human body [14,43,49], or emotional state [48,22,13]. Studies have manipulated matches between user activity types and ambient light [31,47,45], namely, the user scenarios.…”

“…For example, precedent studies have varied the color hue of the ambient light and followed passengers' responses by comparing electroencephalogram (EEG) and self-assessment results [41,22]. Studies have also examined bright blue light's therapeutic effect and collected EEG with subjective responses [14,43]. The effect of light influences industrial applications, including car interior light, when integrating the physiological and psychological responses.…”