Visibility monitoring using conventional roadside cameras : shedding light on and solving a multinational road safety problem

The measurement of atmospheric visibility is an important element for road and air transportation safety. We propose in this paper a novel estimator of the atmospheric visibility by already-existing conventional highway cameras, with a technique based on the gradient magnitude obtained by applying Lambert's law with respect to changes in lighting conditions. The response of this estimator is calibrated by non-linear regression with data from a visibility meter installed in a test site which has been instrumented with a camera. Through our technique, atmospheric visibility estimates are obtained with an average error of 30% for images taken in the day, with lighting conditions between to 8,000 cd.m-2 and visibility distances up to 15 km. Our emerging results indicate that a primary next step could be to deploy on current or future roadsides a practical implementation of our research results to determine local visibility for the benefit of drivers and the safety of our roads, while addressing the needs of meteorological observation and of air quality monitoring