Effects of the Wet Retroreflectivity and Luminance of Pavement Markings on Lane Departure Warning in Nighttime Continuous Rain with and without Glare Sources
To be published on April 2, 2019 by SAE International in United States
A common challenge for both machine vision (MV) systems based on visible-spectrum cameras and for human drivers is detection of pavement markings in nighttime rainy conditions. This occurs because a layer of water refracts the light differently than air, causing conventional markings to substantially retroreflect the light away from the driver or camera when the marking is immersed. This reduces the marking retroreflectivity in wet conditions, and thus the contrast in the image collected by the camera at longer viewing distances. MV lane departure warning (LDW) systems also depend on pixel data from shorter viewing distances; the contrast here also depends on the luminance (Cap Y (CIE)) of the marking, which typically is reduced if the marking is soiled or worn. The efficacy of LDW systems are also known to be influenced by the presence of glare, as regions of glare test the limits of the high dynamic range of the sensor and reduces the contrast between the marking and the surrounding roadway surface. In this study, the authors explored the effects of wet retroreflectivity and luminance of white and yellow markings on the detection performance of a Mobileye LDW system in continuous nighttime rain conditions supplied by a rain tunnel. Pavement marking samples were evaluated in the absence and presence of glare sources, which included vehicle headlamps and taillights. LDW performance is reported as confidence level of marking detection and accuracy of classification of markings for the various testing conditions. Detection confidence level was found to correlate with the level of pavement marking wet retroreflectivity in the absence of glare. In the presence of glare, the confidence of detection of the markings on the edge opposite the glare sources correlated with the level of wet retroreflectivity.