This paper evaluates the detectability of the phantom array and stroboscopic effects during light source motion, eye movement and their combination, using time modulated light-emitting diode light sources. It is well known that the phantom array can be observed when time-modulated light sources are observed during saccadic eye movements. We investigated whether light source motion can cause similar effects when the subject has fixed eyes. In addition, we estimated the detectability threshold frequency for the combination of stroboscopic effect and the phantom array, which is named the stroboscopic-phantom array effect, during two eye movements in opposite directions under one directional rotating light source with variable speed. Our results indicate that one of the most important factors for the stroboscopic-phantom array effect is eye movement speed relative to the speed of the light source. Therefore, time-modulated moving light sources induce a stroboscopic effect in subjects with fixed eyes that is similar to the stroboscopic-phantom array effect observed during saccadic eye movement. Our findings are likely to be useful for predicting the stroboscopic effect and the stroboscopic-phantom array effect during the fast motion of time-modulated LED light sources, like multi-functional rear lamps, in automotive lighting applications.

Traffic crashes frequently occur at intersections because drivers or pedestrians cannot properly anticipate the direction towards which other vehicles are turning. A turn signal guide lamp was developed to improve the observer’s direction judgement of turn signals, and experiments were conducted to test the effect of the guide lamp based on behavioural responses. Our experimental results demonstrated that the turning direction judgement response time was reduced when both the turn signal indicators and turn signal guide lamps were used together compared with the case when only the turn signal indicators were used. Supplementary eye-tracking data also demonstrated that the gaze point frequently stayed on the light patterns on the ground marked by the turn signal guide lamps. Additional glare evaluation using the de Boer scale showed no significant difference between the turn signal indicator with a guide lamp and the turn signal indicator alone on dry or wet road surfaces. Therefore, it is expected that the newly developed turn signal guide lamp will increase the observer’s performance of direction judgement on the turn signalling function without causing an additional glare when the observer knows the function of the guide lamp.