Estudo da possibilidade de ocorrência de Hidroplanagem em estradas portuguesas

Hydroplaning occurs when the tire loses contact with the pavement due to the presence of a water film, causing lost of steering control by the driver, and it is pointed out as a major cause of road accidents. In Portugal, road design standards do not define how to assess hydroplaning risk and how to mitigate it. This paper presents a study on the conditions hydroplaning occurs for the Portuguese rainfall characteristics, the road geometry imposed by national road design standards and the pavement surface layer characteristics. It was used as case study a highway widening project. Hydroplaning risk was assessed by determining hydroplaning velocity (maximum driving velocity before hydroplaning happens) variation within the road section (length and width). An algorithm was programmed on MATLAB to determine the path of rain drops on pavement since it falls to the instant it leaves the pavement by sides (water collection system). The pavement influence was evaluated by considering two different surface solutions, asphalt concrete (impervious) and porous asphalt. For all the situations the risk of hydroplaning rises with road width as more draining area means larger water film thickness. In horizontal straights the risk rises with vertical gradient due to low transversal gradient. In horizontal curves the risk is lower than other sections due to superelevation (usually high transversal values). In transition zones, between straights and curves, there is the higher risk due to very low transversal gradients, especially on large transition lengths. Regarding surface layer type, porous asphalt reduces the risk but if conservation of permeability is not assured the risk can be higher than with common asphalt concrete surface layers. In the situations of higher hydroplaning risk some technical solutions are proposed and discussed.