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The objective of this paper is to study the operational characteristics of exclusive double left-turn lanes at signalized intersections. Data for exclusive double left-turn lanes were collected at seven signalized intersections with protected signal phases in Beijing, and the influence of lane usage and u-turning performance on double left-turn operations were analyzed. Results showed that the proportion of lane utilization was 50 percent in both of lanes for a double left-turn and that more heavy vehicles tend to use the outside lane. The observed saturation flows yielded a mean saturation flow of 1665 passenger cars per hour of green per lane (pcu/h/ln) with a saturation flow interval of 1587 - 1818 pcu/h/ln. Also, the saturation time headway between the inside and outside left-turn lanes were analyzed using independent sample T-tests. It was concluded that there was no significant statistical difference between the outside lane and the inside lane. In order to analyze the effect of u-turning on left-turn saturation flow rates, the concept of u-turning passenger car equivalent (UTPCE) was introduced, and it is revealed that the UTPCE is 1.39. Finally, the u-turning adjustment factor for the left-turn saturation flow rate is developed. © 2010 ASCE.
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