Simulation of Impact of Water-Film Spray on Visibility

Abstract

On rainy days, large rain particles in the air block and scatter the light so that visibility on roads decreases. However, it is conventionally ignored that the spray caused by high-speed vehicles with the existence of water film on pavement also creates visibility issues. In this study, a model to calculate the spray concentration was established. Monte Carlo simulations were performed to characterize the stochastic process of the weakening light-transmission phenomenon due to spray. Combining Mie scattering theory and the definition of visibility in meteorology, the visibility reduction due to the spray created by water film at different vehicle speeds was quantified. Simulation results indicated that the effect of spray on visibility is approximate to that of heavy rain when the water-film depth is 5 mm. The visibility generally decreases with the increase of vehicle speed and water-film depth. However the former has greater influence on visibility compared with the latter. To ensure visibility at water-film depths of 5, 2.5, 1, and .5 mm, speeds should be controlled below 93, 96, 11, and 16 km/h, respectively. The developed model can be useful in understanding and estimating the influence of spray on visibility and help formulate a low-visibility warning strategy.