Determining flow density asymmetric curve using direct empirical approach

Several functions are available to fit flow-density data of traffic flow. These include the two-regime method, the reversed lambda method, the inverted “V”method, the parabolic method and the asymmetric method. The first three methods are weak in explaining traffic behaviour in the congested region. In the latter two, the asymmetric method which recognizes different behaviour for traffic in the free and constrained states was used in this study. The trajectory of the asymmetric flow-density curve was used to predict the capacity of the highway section and subsequently the jam state was computed. Data was collected on a principal road in free flowing condition and was used to validate the model. The results show good fit to the model with R2= 0.89.The paper concluded that flow/density curve could be fitted using direct empirical approach