Abstract: For the shortcomings of Pacey's platoon dispersion model weakly reflecting partial normal distribution in the field situtation, from the density view, the authors developed a platoon dispersion model by assuming the speed following lognormal normal distribution.The model described how statistical characteristics of speed for queuing vehicles at the upstream intersection affected spread of cars along the downstream road, as the platoon moved from an upstream at green phase end time.It could provide traffic data for signal timing plans of the downstream intersection.Finally, numeric computation for coordination of successive signals was presented to illustrate validity of the proposed model.