Signal Optimization Method for Car-and Truck-separation Management at Intersections on Port Access Roads
Container trucks are common on port access roads;they are heavy,slow,and have a long braking distance.Container trucks at a high quantity reduces the operational efficiency at signalized intersections on port access roads and causes greater security risks.To improve both traffic safety and efficiency at signalized intersections,this study redesigns the intersection layout and the corresponding signal phase scheme to accommodate car-and truck-separation.A nonlinear integer programming model is established to reduce the number of left-through collisions and the average delay of both cars and trucks,and a corresponding genetic algorithm is designed to solve the model.To fully consider the effect of vehicle type,"vehicle per hour"is used as the unit of truck flow.An intersection on a port access road in the Lingang New Area within the Shanghai Pilot Free Trade Zone is selected to validate the method,and the current scheme is compared with the optimized mixed car-truck and car-and truck-separation schemes.The results show that the car-and truck-separation scheme not only effectively reduces left-through conflicts but also decreases the average delay of cars and trucks.Compared with the current scheme,the optimized scheme reduces the number of left-through conflicts by 5.14 times·h-1,the average car delay by 27.5 s,and the average truck delay by 29.6 s.Additionally,the effect of the weights of three objectives on the car-and truck-separation scheme is investigated.The results show that when the weight of the number of collisions is in the interval of[0.2,0.4]and the ratio of car to truck delay weights is 2∶5,the car-and truck-separation scheme performed better.Additionally,the effect of the car-to-truck volume proportion on the car-and truck-separation scheme is investigated.The results show that the average numbers of cars and trucks first increased and then stabilized,whereas the number of left-through conflicts decreased with the number of trucks.The proposed method can effectively improve and balance the traffic efficiency and safety at signalized intersections on port access roads.
traffic engineeringtraffic signal controlcar-and truck-separationport access roadleft-through conflictdelay