Experimental validation of dedicated methods to in-vehicle estimation of atmospheric visibility distance

In the framework of the French Research Action for Secure Driving (ARCOS) Project, we developed a system that uses in-vehicle charge-coupled device (CCD) cameras, aiming to estimate the visibility distance in adverse weather conditions, particularly fog situations. The topic of this paper is the validation of the system. First, we present Koschmieder's model of apparent luminance of objects observed against the background sky on the horizon and deal with the definitions of the different visibility distances we use in our measurement framework, as well as the links that bind them. Then, we describe the two specific onboard techniques we designed to estimate the visibility distance. In the third section, we present a dedicated site and how we use it to validate the previous techniques. Finally, we give the results of a quantitative validation of our onboard techniques, using actual pictures of the validation site in foggy weather