Analysis of scale-free characteristic on sharp variation point of traffic flow

Traffic flow time series at different time scales have different fluctuation characteristics. In order to analyze the discontinuity characteristics of traffic flow, a traffic volume time series is adopted as an empiric study objective. The multi-scale sharp variation points of the sequence are obtained by using wavelet transform. The scales are divided based on the corresponding number of the zero-crossing points of wavelet transform, and the hierarchy of the scales is analyzed. The results of calculation indicate that the number of sharp variation points of the traffic flow on a mutation scale is self-similar in a certain scale if the number of the sharp variation points is used as a measure. So, sharp variations of the traffic flow in different scales are scale-free.