Abstract:To make the intelligent traffic systems (ITS) work well,it needs to obtain the core traffic parameters,including the flow,speed,density,and so on.There are a lot of methods to detect the core traffic parameters currently.But,none of them can detect all of the core parameters at once.Especially,the density is difficult to be detected.There is only a few methods focusing on detecting the density in a local sense.As for in the global sense,there is not yet any feasible method.The detection methods were summarized from three aspects,such as the flow,density and speed.Those references which suggest that traffic parameters can be easily detected only by the video were studied deeply.