Retroreflectivity measurement system

A retroreflectivity measurement system comprising a structure arranged to be mounted to a front of a vehicle, the system comprising:

• at least one light source mounted on said structure and arranged to substantially continuously project light across at least a portion of a traffic lane at a specified distance from the vehicle during a measurement run, the light being limited to a particular portion of the visible light spectrum;
• a camera apparatus mounted on said structure in spaced apart relationship to said at least one light source and having a field of view including at least a portion of said traffic lane illuminated by said light source during said measurement run, the camera apparatus being selectively sensitive to light at said particular portion of the visible light spectrum to provide first filtered images of at least a portion of said illuminated portion of the traffic lane and said camera apparatus being separately selectively sensitive to light at least at one portion of the spectrum not including said particular portion to provide second filtered images of said illuminated portion of the traffic lane;
• and
• a controller arranged to:
• a) obtain sequences of first and corresponding one or more second filtered images from said camera apparatus during said measurement run;
• b) identify within at least one of said sequences of images, at least a portion of a road marking illuminated by said light source;
• c) determine a first intensity of said at least a portion of the road marking from a first filtered image containing said at least a portion of the road marking;
• d) determine a further intensity of said at least a portion of the road marking from the corresponding one or more second filtered images;
• e) estimate an ambient intensity of said at least a portion of the road marking within said particular portion of the light spectrum, by applying a scaling factor to said further intensity;
• and
• f) determine a retroreflectivity of said at least a portion of the road marking as a function of said first intensity and said estimated ambient intensity.