The use of left-turn waiting area has been extended in many cities. In order to avoid the abuse of it, this thesis describes the common steps of setting left-turn waiting area, by taking intersection geometry, the direct moving and left-turn traffic flows into consideration. In addition, quantitative analysis can be made on setting waiting area and then the threshold of the length of waiting area would be concluded according to the shortest green light interval. By using different parameters, this thesis makes comparisons on the influence of the waiting area on traffic efficiency with and without a waiting area. Finally the measuring data selected at an intersection in Nanjing are analyzed. The results show that this example satisfies the conditions of waiting area's setting. Without changing other conditions, the capacity of intersection which uses left-turn waiting area is increased by 20%, with the delay time of average vehicle shortened. Therefore, discussing the setting conditions of waiting area is critical to promoting the traffic efficiency.
