## Optimal location of the U-turn at a signalised intersection with double left-turn lanes

The location of the U-turn median opening at signalised intersections can have important effects on the intersection performance. However, there has been very little prior work on this issue, especially on intersections with double left-turn lanes. This study analyses the mutual interference of the U-turn and the left-turn movements at signalised intersections with double left-turn lanes. A lane selection model, based on the Wardrop Equilibrium Principles is developed for left-turn drivers. The saturation flow rate model of the double left-turn lanes is developed to quantitatively evaluate its utilisation. This study also presents the guidelines for the design of the U-turn median opening for maximising the saturation flow rate of double left-turn lanes. The proposed model is also verified by means of simulation, and then a case study is used to compare the intersection performance before and after optimisation. The results of case study show that if the U-turn locations are varied, the saturation flow rate of the double left-turn lanes would also vary considerably. The authors show that there can be a major difference of 77.47%, and the saturation flow rate of optimal location can be improved by 7.63% compared with the current location of the U-turn median opening.