Automated Mobile Highway Sign Retroreflectivity Measurement

This paper presents a mobile image-based system for measuring the brightness of highway signs at night time, so that visibility standards for sign can be evaluated and maintained to protect the safety of the motoring public. The system is composed of a high speed IEEE-1394 digital camera, and a laptop computer with a purpose-designed measuring software, which is composed of three modules:1) Image and video processing; 2) Image analysis; 3) data storage. Using vehicle headlamps as an illumination source, the system can acquire, classify, and analyze the visibility of the traffic signs in real time, and report results to a data file. The analysis algorithms, including elements of sign isolation, classification, and intensity measurement, are designed for easy implementation and fast real-time measurement. The results of static testing experiments on signs, and on-road real time measurements are describe in this paper and they show the feasibility of such a system.