Assessment of Impact of Splash and Spray on Road Users: Results of Controlled Experiment

Abstract

A preliminary field test assessed the impact of splash and spray on road users. The test was part of a larger project sponsored by FHWA to develop a model that could characterize a highway's propensity to generate splash and spray during rainfall and the impact of this on road users. “Splash and spray” refers to water thrown into the air when a vehicle tire crosses a wet surface. For the experiment, participants observed videos recorded from the driver position of a vehicle as it traveled behind another vehicle in rain conditions. The videos were recorded on the Virginia Smart Road, and the rain conditions were created with a weather-making system. The full factorial design used two levels for each of the five variables: driver vehicle, spray vehicle, maneuver, rain rate, and speed. Participants rated each video for five categories: obstruction, concentration, confidence, control, and risk. In addition, an objective measure of visual obstruction, the occlusion factor, was recorded. Several factors and interactions were found to be significant for the subjective ratings, but significance varied depending on the category being rated. The occlusion factor was found to have a strong correlation with each of the ratings, and the lowest R2 value was .75. This correlation result suggests that the occlusion factor could be used to predict user perceptions of splash and spray.