New Horizons of Science, Technology and Culture Vol. 10

Outdoor Trespass Lighting (OTL)—the unintended intrusion of artificial light into residential environments—has emerged as an increasingly significant environmental, health, and urban design concern as high-intensity LED lighting systems proliferate globally. Current outdoor lighting standards primarily evaluate OTL using vertical illuminance measured at the property line or building facade. However, this metric does not necessarily reflect the optical stimulus actually entering the human eye, particularly when outdoor luminaires are directly visible from residential windows. This study develops and validates a mathematical formulation for estimating Eye Corneal Illuminance (ECI) generated by outdoor luminaires under typical roadway lighting geometries. The proposed formulation is derived from fundamental photometric principles, including the inverse-square law and the cosine law of illumination, and incorporates the luminaire luminous intensity distribution, mounting height, and observer viewing geometry. The derived equation was verified using both manual photometric calculations and computer-based lighting simulations. Results demonstrate strong agreement between analytical and simulation-based calculations, confirming the validity of the proposed formulation. The analysis further shows that eye corneal illuminance may equal or exceed conventional vertical illuminance values under direct line-of-sight conditions, indicating that façade-based metrics may underestimate the light stimulus reaching occupants. The study proposes that ECI be considered alongside traditional photometric standards in outdoor lighting. Measuring light at the corneal plane allows for a more relevant assessment of visual comfort, circadian effects, and residential well-being. The proposed framework contributes to the development of human-centric outdoor lighting design methodologies that balance public safety with environmental and health considerations.