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The location of the U-turn median opening at signalized 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 signalized i...
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... Scholars have discussed the key influences affecting the position of median openings, highlighting the growing demand for U-turns as a crucial factor [9]. At the same time, researchers have utilized the critical gap [10,11] and various configurations of lanes [12] as the parameter, respectively, to calculate the optimum location for the median opening. Some researchers have assessed the performance of median openings from the safety and crash perspective [13]. ...
As the number of motor vehicles in China’s cities continues to increase, the imbalance between the capacity that existing urban roads have for construction and the demand for motor vehicles is becoming increasingly evident. Indeed, the design of the intersection U-turn scheme has garnered significant attention from researchers. However, as the number of vehicles requiring U-turns increases, the traditional U-turn in the median or U-turn at the intersection fails to meet the timely demand for U-turns. In such cases, vehicles needing to make U-turns are required to queue first. As the queue length grows, it ultimately impacts the operational efficiency of the intersection. To optimize the imbalance between supply and demand at these intersections and promote the sustainable development of intersections, an innovative form of U-turn organization called the Parallel U-turn has been developed. In the engineering practice of reconstructing existing intersections or constructing new ones, it is crucial to investigate the compatibility between various U-turn design forms and traffic volumes. This exploration helps ensure that the chosen U-turn design effectively accommodates the specific traffic demands at the intersection. Therefore, in this paper, a typical intersection in Xi’an was chosen as the study intersection to investigate traffic data. The researchers calibrated and simulated four U-turn organization schemes using VISSIM microsimulation software. The four schemes included a traditional U-turn at the intersection, a Parallel U-turn at the intersection, a traditional U-turn in the median, and a Parallel U-turn in the median. Then, the researchers used the entropy-weighted TOPSIS method (EWTM) to evaluate the compatibility of each U-turn organization scheme for different traffic combinations. This assessment was conducted based on three criteria: operational efficiency, environmental protection, and safety performance. The results of this study indicate that the Parallel U-turn design is advantageous for the XiaoZhai intersection in Xi’an, China, under specific traffic conditions. When the traffic volume at the intersection exceeds 5940 vehicles per hour but remains below the intersection’s maximum capacity, implementing the Parallel U-turn design could yield positive outcomes in terms of operational efficiency, safety performance, and a reduction in intersection pollution. In summary, by enhancing operational efficiency, safety, and environmental impact, the Parallel U-turn design promotes the overall performance and sustainability of the XiaoZhai intersection and the transportation system in Xi’an, China.
... On Chinese urban roads, the transformation of lane function is mainly used to achieve the transfer of traffic flow. It is a highly targeted control tool for turning tidal traffic to improve the efficiency of road traffic [1][2][3]. However, during the process, some drivers are unable to obtain effective information in time, generating problems such as lane-changing decision errors and low lane utilization. ...
... The proposed STCA-V model above correlates the lane-changing and the function change of variable direction lanes with the vehicle queue length at the inlet through Equations (3)(4)(5)(6)(7)(8)(9)(10)(11)(12) and utilizes the speed guidance under vehicle-road cooperation to improve the synchronous phase of traffic flow on the road section. The corresponding operating rules for the vehicle i at moment t+1 are designed as follows. ...
... Step 5: The random slowing process is as follows: (17) Step 6: The vehicle queue and the dissipation process are described in Section 3.2.2, refer to Equations (3)(4)(5)(6)(7)(8). ...
In this paper, we propose an improved cellular automaton model for the traffic operation characteristics of variable direction lanes in an Intelligent Vehicle Infrastructure Cooperation System (I-VICS). According to the proposed flow of variable oriented lane operation in the I-VICS environment, the idea for the improved model has been determined. According to an analysis of different signal states, an improved STCA model is proposed, in combination with the speed induction method of I-VICS and the variable direction lane switching strategy. In the assumed regular simulation environment, the STCA and STCA-V models are simulated under different vehicular densities. The results indicated that traffic parameters such as traffic flow and average speed of the variable direction lanes in the I-VICS environment are better than those in the conventional environment according to the operating rules of the proposed model. Moreover, lane utilization increased for the same density.
In urban traffic systems, alleviating traffic congestion originated from left-turn/U-turn lanes at highly demanded intersections plays an important role in enhancing the traffic efficiency. For a typical intersection, the layout with double left-turn (DLT) lanes is a relatively common geometric feature. However, the effect of DLT scheme on the performance of the entire traffic system is not clear. This paper compares the performance of urban traffic system with different lane function schemes with extended cellular automaton (CA) model considering the car-following, lane-changing, intersection-traversing and route-choice behavior of vehicles. Using the flow-density relation, three macroscopic parameters (average trip completion rate, average traffic flow and average velocity) are examined to evaluate the system performance. With the wide application of DLT scheme, the vehicles can be distributed more evenly among the lanes. As a result, the traffic flow and the trip completion rate will be higher, especially at high density. Case studies of realistic Hefei city network and Sioux Falls networks are also carried out. The results show that the performance of traffic network will be better if more intersections adopt the DLT scheme.
