Capacity of exclusive dual left-turn lanes at signalized intersection

Based on the survey data of six signalized intersections with dual left-turn lanes in Beijing,the saturation time-headways,saturation flow rates and their influencing factors of dual left-turn lanes at signalized intersections were studied by using statistical methods.By comparing with arithmetic mean value and median value,the trimmed mean value method was used to calculate the saturation time-headway and saturation flow rate.The effects of lane width and turning radius on the saturation flow rate were studied,and the regression model of saturation flow rate with turning radius was suggested.The saturation flow rates of inside lane,outside lane and single left-turn lane were compared.Analysis result shows that the saturation time-headway of inside lane is 2.14~2.60 s,the saturation time-headway of outside lane is 2.08~2.37 s,and the average saturation flow rate is 1 600 pcu·(h·lane)-1.The ratio of sum saturation flow rate of inside lane and outside lane to that of single left-turn lane is 1.80~2.05.6 tabs,1 fig,11 refs.