Analysis of the visibility of vertical road signals under different conditions using innovative technologies

Vertical road signs are essential for guiding and protecting road users. Their effectiveness relies heavily on visibility, especially at night or in adverse weather, when retro reflective materials ensure readability by reflecting headlights back to drivers. However, over time, environmental factors such as rain, dirt, and sunlight degrade these materials, reducing visibility and increasing safety risks. Italian and European standards (e.g., UNI EN 12899-1 and UNI 11480:2016) require that signs be replaced once performance falls below set thresholds. This thesis presents an experimental study conducted at the “Enzo e Dino Ferrari” Autodrome in Imola, aiming to assess how different retroreflective conditions affect driver perception. A total of 15 drivers completed two laps of a test circuit equipped with six signs under varying conditions: clean, degraded, dirty, wet, frosted, and high-performance (Class 3). Each sign was evaluated under both standard (N series) and altered (V series) conditions. Eye tracking (TOBII Pro Glasses 3) and vehicle telemetry (RACELOGIC Video VBOX) recorded driver behavior. Data analysis focused on metrics such as recognition distance, velocity variation, fixation duration, and fixation count. Results show that degraded retro reflectivity led to delayed sign recognition and reduced driver attention, while high-performance materials significantly improved detection and engagement. The findings confirm the importance of maintaining retro reflective quality for road safety. This study supports improved monitoring practices and strategic material selection to enhance visibility, reduce accidents, and promote sustainable mobility.