Pavement marking in daylight with poor quality cannot provide a reference for drivers to specify their own position relative to nearby vehicles. Luminance and Correlated color temperature (CCT) of sunlight is of importance for daytime visibility of in-service pavement markings, which lacks detailed consideration. This paper aims to explore the daytime visibility requirements of in-service pavement markings considering the influence of natural light characteristics. Based on analyzing the mechanism and impact factors of daytime visibility of pavement markings, a subjective scale of pavement markings state in the drivers’ field of view was proposed and a short and bold line was recommended as the standard state. Thirty-six tested drivers were randomly selected to detect white and yellow markings of both 15 cm and 20 cm width under 2000 to 23,000 lx and 5500 to 8500 K for outdoor natural light environment. The luminance contrast of the pavement marking to the surrounding road surface ranged from 0 to 10. The result indicated that the natural light with 2000 to 3000 lx and 7500 to 8500 K is the most unfavorable light environment for drivers to recognize pavement markings during daytime. The detection distance is becoming longer with the increase of luminance contrast. The detection distance does not increase with the increase of luminance contrast when the luminance contrast of white markings is greater than 4 and that of yellow markings is greater than 3. The model was established expressing the relationship between luminance contrast and Q_d contrast. The preview time 3.65 s was selected to calculate the minimum requirements of Q_d at speeds of 60, 80, 100 km/h, respectively, for different types of markings. The results can provide scientific evidence for quality evaluation and maintenance management of pavement markings in service for daytime visibility.

Pavement markings are critical traffic safety facilities that provide continuous and clear visual guidance to road users, thereby supporting traffic order and driving safety. During long-term service, however, white pavement markings are prone to yellowing under ultraviolet (UV) irradiance and elevated temperatures, which may reduce visibility. This study conducted accelerated aging tests on white thermoplastic and two-component pavement markings under four levels of ultraviolet irradiance (0–1.5 W/m² at 340 nm) and temperature (20–80 °C) to quantitatively characterize the macroscopic evolution of yellowing (YI) under controlled environmental conditions. Generalized linear mixed-effects models (GLMMs) were then used to quantify the effects of UV exposure, temperature, and time on the yellowing behavior of white pavement markings. The results indicate that temperature is a key environmental driver of YI increases. UV irradiance also has a pronounced promoting effect, and the yellowing responses differ markedly between material types. The results clarify how UV irradiance, thermal conditions, and material systems jointly influence the yellowing behavior of white pavement markings, providing a scientific basis for evaluating anti-yellowing performance, improving durability design, and guiding engineering applications under complex environmental conditions.