Transition to LED road lighting: Impact on visual performance and pedestrian recognition

Light emitting diode (LED) road lighting and the impact of correlated colour temperature (CCT) variations in comparison to traditional high pressure sodium (HPS) road lighting on driving-related human factors was the focus of this research. This work is highly relevant for road authorities, transitioning from traditional high intensity discharge to LED road lighting, as they make choices including which CCT types to select. This night-time field-based study measured visual performance and pedestrian recognition under three road lighting conditions: LED (3000 K, 4000 K) and HPS (2000 K), for 20 young visually normal participants ( M = 25 ± 3 years). Visual acuity (VA) and contrast sensitivity (CS) were assessed using customized charts, and time to first recognize pedestrians wearing non-reflective clothing walking towards the road was recorded at two distances for participants positioned in a stationary vehicle. There were no significant differences in VA or CS between road lighting conditions; however, pedestrians were recognized significantly sooner under HPS than either of the LED road lighting conditions (3.6 s sooner under HPS compared to 4000 K LED), likely due to the greater lateral spatial light distribution from the HPS used in this experimental study. Road lighting design using LED luminaires needs to consider the impact of their potentially sharper luminous cut-offs and provide designs with appropriate characteristics and dimensions.