Modelling Spatial-temporal Resource Optimization For Intersections With One-to-multi-lane Left-turn Waiting Areas

The left-turn waiting area is a channelization way for urban intersections,which helps to alleviate driving anxiety.When one-to-one-lane left-turn waiting area is set,especially when the length is short,the traffic emission and vehicle delay will increase due to the second stop.However,when the internal space of the intersection is large enough to allow the setting of one-to-multi-lane left-turn waiting area,the traffic emission and vehicle delay can be reduced due to the improvement of traffic capacity.This study focuses on the critical setting conditions of one-to-multi-lane left-turn waiting areas and the signal timing optimization models considering left-turn short lanes and one-to-multi-lane left-turn waiting areas.Firstly,considering the spatial layout and traffic flow,the potential conflicts between traffic flows are analyzed,and the geometric and flow critical conditions for adding one-to-multi-lane left-turn waiting areas at intersections are proposed.Secondly,considering the left-turn short lanes and left-turn waiting areas,for one-to-multi-lane left-turn waiting areas,the calculation formulas of saturation flow rate,capacity and average vehicle delay of an entrance lane group are modified,and the calculation formulas of vehicle emission factors for an entrance lane group during green and red are also modified;Furthermore,taking the effective green times as the decision variables and the minimum vehicle delay and traffic emission as the objectives,the signal timing optimization models of an intersection(group)are established.Finally,the intersections of Datun-Beichen East Road and Datun-Anli Road in Beijing are selected.Considering the channelization,phase sequence and timing scheme of the intersection,a variety of comparative experimental schemes are designed.With the help of the microscopic simulation software VISSIM,traffic flow operations are simulated,and the pollutant emission,average vehicle delay and number of stops are selected as the performance indexes;using the multivariate statistical analysis,the sensitivity of traffic efficiency and vehicle emissions to setting one-to-multi-lane left-turn waiting areas and the effectiveness of the signal timing optimization model are studied.The results show that,for an isolated intersection,the proposed signal timing optimization model can reduce traffic emissions,average vehicle delay and number of stops by 26.55%,6.94% and 14.46% on average;after adding one-to-one-lane left-turn waiting areas before the left-turn short lane,the traffic emission,average vehicle delay and number of stops increase by5.96%,11.27% and 7.89% on average;setting one-to-two-lane left-turn waiting areas and one-to-three-lane left-turn waiting areas in front of left-turn short lane can reduce traffic emissions by 5.88% and 5.37%,average vehicle delay by 1.36% and 1.83%,and number of stops by 0.44% and 3.16%,respectively.For an arterial road system,the proposed signal timing optimization model can reduce traffic emissions,average vehicle delay and number of stops by19.75%,32.03% and 15.37% on average;after adding one-to-one-lane left-turn waiting areas in front of the short lane,the traffic emission,average vehicle delay and number of stops increase by 4.76%,8.23% and 2.53% on average;one-to-two-lane left-turn waiting areas in front of short lanes can reduce traffic emissions,average vehicle delay and number of stops by 9.32%,4.90% and 3.8% on average.In conclusion,if the intersection space is limited,it is not recommended to set one-to-one-lane left-turn waiting areas;if the intersection is located under the bridge pier and the space is large enough,it is suggested to set up one-to-multi-lane left-turn waiting areas,and use the proposed intersection timing optimization model,so as to maximize the use of intersection spatial-temporal resources.