In the process of video-based traffic detection system design

from the view of establishing the congruent relationship between output signal of virtual sensor and the actual traffic volume

analysis and study is carried out.A new design of the virtual sensor is put forward and pre-processing algorithm for information extraction and judgment method of valid information is improved

so as to avoid some shortcomings of traditional design such as considerable consumption of hardware and software resources in the process of valid information extraction

all of those shortcomings are caused by unreasonable design methods of virtual sensor and unscientific algorithm of information processing in traditional design.The experimental result shows that the revised design has enhanced the adaptability and robustness of the whole system to illumination change

the complexity of the road and the surrounding environment.