Abstract: At the traffic planning stage, the traffic assignment results need to be evaluated. At present, only the saturation ratio index is used to evaluate static traffic assignment results, which is not profound. Based on the traffic theory, the "side peak" function of traffic volume and travel time was deduced, and concepts of arriving traffic and through traffic were introduced for traffic assignment simulation method according to the "side peak" impedance function. The average arriving saturation rate and delaying ratio as two major index to weigh road network level of service were proposed.