Xiang Xiaowei
Guangxi Qinzhou Municipal Bureau of Natural Resources
Abstract: The coordination and control optimization of cross-river bridges and regional transportation networks along rivers can reduce the congestion of trunk lines and key intersections, and greatly save manpower and time costs. Taking the Yongfu Bridge and Zicai Bridge of the Pinglu Canal in Qinzhou and the regional transportation network along the river as the research object, the optimization method of timed traffic signal cooperative control method and adaptive traffic signal cooperative control method was proposed, and the method was simulated and tested and compared with the example analysis. The results show that the optimization effect of the timed and adaptive traffic signal cooperative control method is greatly improved compared with the original effect, and the effect of reducing the delay time of vehicles is better.
Keywords: coordinated control; bridges across rivers; traffic signals; regional transport networks;
About author:XIANG Xiaowei (1984—), female, from Nanning, Guangxi, master's degree, engineer, research direction is urban transportation planning.
0 Introduction
With the development of social economy, the construction of urban transportation infrastructure along the river is accelerating, and the two banks of the river are frequently connected by cross-river bridges, cross-river tunnels and other facilities, and due to the limited traffic capacity that bridges, cross-river tunnels and other facilities can accommodate, it often leads to cross-river bridges and other cross-river passages becoming the most prone to congestion. Although the congestion problem can be solved in the short term by building public facilities such as cross-river bridges, it will not change the current situation of the weak point of the transportation network in the long term [1]. Therefore, studying the traffic characteristics of the cross-river transportation network and formulating reasonable management measures are the key points to fundamentally improve the weakness of the cross-river bridges and the regional transportation network along the river.
In this regard, many scholars have optimized the city's cross-river bridges and the transportation network along the river. Huang Peibei [2] proposed a dynamic discrete model of urban traffic for application control based on the nonlinear characteristics of urban traffic, and simulated the actual traffic volume data in the central area of Shanghai to verify the feasibility of the model. Sun Youxin [3] designed a regional traffic control system according to the characteristics of urban traffic network loops, and found that the system can have a certain effect on vehicle delays and reduce the number of parking times through the analysis of examples. Wu Xiongtao [4] analyzed the congestion points of the Yibin cross-river bridge, proposed a traffic organization scheme, and verified the scheme through a simulation model, and found that the congestion time was significantly reduced and the average driving speed was significantly improved. Liu Qin [5] established a traffic control model based on the waiting and output of vehicles at intersections, and used particle swarm optimization and annealing algorithm to simulate the simulation, and found that the control effect of the proposed model was better than that of the TRANSYT model in all aspects. Although scholars have carried out optimization analysis and model simulation of various types of cross-river bridges and cross-river passages from various aspects, there are few studies from the perspective of regional traffic signal coordination.
In this paper, taking the Yongfu Bridge and Zicai Bridge of the Pinglu Canal in Qinzhou City and the surrounding transportation network along the river as the object, the timing and adaptive control methods for the cross-river bridges and the areas along the river are proposed, and the optimization effect of the main trunk line, regional boundary, key trunk line and key intersection is analyzed for simulation, so as to verify its feasibility and provide a certain reference for practical application.
1 Background Overview
The Pinglu Canal is the main channel connecting the Xijiang shipping line and the Beibu Gulf, which will shorten the length to the sea and reduce the transportation cost. According to the relevant planning and design, most of the Pinglu Canal will be renovated by using the existing Shaping River and Qinjiang River, of which 6km of river channel in the watershed is a fully excavated section. The water level difference of the whole canal is about 60m, and 4~6 steps are preliminarily selected, and the construction is carried out according to the standard of inland river I. class waterway and navigable 5 000t class cargo ships and 3 000t class sea vessels, and the total investment budget of the project is about 60 billion yuan. After the completion of the Pinglu Canal, the length of the sea from Nanning to Qinzhou Port through the Pinglu Canal is only 291km, which greatly shortens the length of Guangxi's inland rivers to the sea (shortened by 563km). After the canalization of the upstream Youjiang, Zuojiang and Hongshui rivers, it is expected to form a new and convenient passage to the sea in the southwest of the mainland with the extensive water and land combined transportation network of the southwestern provinces, which will solve the bottleneck problem of insufficient transit capacity of the Changzhou hub to a certain extent.
After the completion of the construction of the Pinglu Canal, due to the improvement of the design standards, the waterway grade was adjusted from the original third-class waterway to the first-class waterway, due to the substantial improvement of the waterway grade, the new bridge was lifted greatly, and the outward movement of the slope and grounding points on both sides of the Pinglu Canal will inevitably lead to great changes in the current traffic connection and construction on both sides of the Pinglu Canal. Therefore, it is necessary to study the future lifting and new construction scheme of the existing bridge cross-river node in Qinzhou urban area, which has a positive effect on ensuring the smooth connection of motor vehicles, non-motor vehicles and pedestrians across the river within the study area after the level of the Pinglu Canal is upgraded, improving the road traffic network in the affected area, improving the overall efficiency of the road network, balancing the traffic load of the regional road network, reducing the traffic pressure of the surrounding roads, and improving the overall service level of the road network.
2 Research Methods and Objects
2.1 Timed collaborative control
Control of the number of cross-river entrances and exits: In order to alleviate the congestion of the bridge during peak hours, the timing constraints are carried out at both ends of the bridge to ensure that the waiting vehicles on the bridge do not exceed the maximum number. The maximum number of waiting vehicles that can be accommodated during a period of a bridge crossing the river is:
In equation (1): Nmax is the maximum number of waiting vehicles that can be accommodated in a period of a bridge across the river; S is the length of the bridge across the river; HD is the front spacing; n is the number of lanes.
Determine the necessity of phase adjustment after obtaining the maximum value of the waiting vehicle, if:
The phase does not need to be adjusted. If:
You need to adjust the green light time for each phase:
In equation (2)~(4): η is the spillover coefficient, generally 0.9; qr is the traffic volume from ramp to bridge (pcu/h); qa is the traffic volume from the intersection to the bridge (pcu/h); gr is the green light time from the ramp to the bridge; ga is the green light time from the intersection to the bridge; trdown is the phase adjustment time from the ramp to the bridge; tadown is the phase adjustment time from the intersection to the bridge.
2.2 Adaptive collaborative control
For the multi-phase adaptive control system, it is necessary to obtain the vehicle distance through actual monitoring, and obtain its saturation through the phase setting factor:
In Eq. (5): SAi,j is the j phase in the i intersection; SAi,j,p is the saturation of the p inlet in the j phase in the i intersection.
Finally, according to the obtained coefficient and saturation, the green light time of each phase is adjusted:
In equation (6)~(7): SAfi,k is the saturation after sorting; Sort_Id is a sorted function.
2.3 Subjects
The research objects are the two river bridges and the main bridge crossing line and the area along the river on the Pinglu Canal in Qinzhou City. The main parameters are shown in Table 1.
Table 1 Main parameters of the bridge crossing the main road of the Pinglu Canal in Qinzhou City Download the original map
2.4 Simulation software
Using the VISSIM simulation software developed in Germany, VISSIM can simulate urban traffic behavior and analyze the operation capacity of urban traffic under different traffic conditions, such as different lanes, different means of transportation, etc., through time interval and on the basis of different driving behaviors, and can systematically evaluate the city and public transportation from a micro perspective. Therefore, VISSIM is currently the most widely used urban transportation capacity evaluation software.
Fig.1 Traffic capacity and delay index of the main trunk line of Vinh Phuc Bridge and Zicai Bridge Download the original map
3 Analysis of results
The optimization effect of the control object is analyzed by the timed and adaptive traffic capacity and delay data output by VISSIM. Among them, the traffic capacity and delay data of Vinh Phuc Bridge and Zicai Bridge are shown in Figure 1.
It can be seen from Figure 1 that the traffic volume from west to east in the main line of the Pinglu Canal is larger than that from east to west, and the traffic capacity of Yongfu Bridge and Zicai Bridge is increased by 24.5%, 23.2%, 22.2% and 18.1% respectively compared with the current situation through the timing and adaptive control methods. Compared with the current situation, the delay indicators of Vinh Phuc Bridge and Zicai Bridge were reduced by 24.1%, 25.3%, 18.2% and 21.6%, respectively. It can be seen that the effects of the two control methods of timed and adaptive fixed period are better than those of the present situation, and the effect of the timed control method is better than that of the adaptive type, which may be due to the fact that the overlap phase of the timed type is stronger than the adaptive type in selecting a certain traffic direction.
Figure 2 shows the overall optimization effect of the controlled area. It can be seen from Fig. 2 that the optimization effect of timed and adaptive fixed period is better in terms of traffic capacity, and the control method under the adaptive change period is reduced compared with the first two. In the delay index, the control method using timed and adaptive fixed-period control methods has a worse effect than the existing control methods, and will produce negative optimization, but in the control method of periodic change, the optimization effect of the adaptive control method is stronger than that of the timed control method.
In addition, the optimization effect of the key trunk lines also needs to be simulated and tested, and the test results are shown in Figure 3.
The optimization effect of key trunk lines is shown in 3. It can be seen from Fig. 3 that the traffic capacity optimized by the timer and adaptive control methods is significantly improved, and the overall effect of the adaptive control method is better than that of the timed control method. The increase and decrease rates of traffic capacity and delay under timing optimization were 17.2% and 14.1%, respectively. The increase and decrease of traffic capacity and delay under the optimization of the adaptive control method are 25.7% and 19.6%, respectively.
The simulation test of three key intersections of the Pinglu Canal and its riverside area is carried out, and the optimization effect is shown in Figure 4. The analysis of the optimization effect of the key intersections 1, 2 and 3 shows that the timing control method and the adaptive control method are generally improved compared with the existing control methods. In view of the traffic capacity and delay indicators, the optimization effect of the adaptive control method of the three key intersections is better than that of the timed control method. The traffic capacity of intersection 1 under timing optimization is increased by 480 pcu/h, and the delay is reduced by 15 seconds. Under the adaptive optimization, the traffic capacity of intersection 1 is increased by 630 pcu/h, and the delay is reduced by 21 seconds. The traffic capacity of intersection 2 under timing optimization is increased by 500 pcu/h, and the delay is reduced by 19s. Under the adaptive optimization, the traffic capacity of intersection 2 is increased by 780 pcu/h, and the delay is reduced by 24 seconds. The traffic capacity of intersection 3 under timing optimization is increased by 600 pcu/h, and the delay is reduced by 16 seconds. Under the adaptive optimization, the traffic capacity of intersection 3 is increased by 980 pcu/h, and the delay is reduced by 21 seconds.
4 Conclusion
In this paper, taking the Yongfu Bridge and Zicai Bridge of the Pinglu Canal in Qinzhou and the regional transportation network along the river as the research object, the optimization method of the timed traffic signal cooperative control method and the adaptive traffic signal cooperative control method is proposed, and the simulation test of the method is carried out and the comparison examples are analyzed, and the following conclusions are drawn:
(1) Compared with the original effect, the optimization effect of the timed and adaptive traffic signal cooperative control method has been greatly improved, and the delay time has been reduced.
Figure 2 Regional boundary indicators Download the original image
Figure 3 Key trunk indicators Download the original image
Figure 4 Key trunk indicators Download the original image
(2) For the main line, the timed traffic signal cooperative control method has a good optimization effect, and the adaptive traffic signal cooperative control method is recommended for the optimization of regional boundaries, key arteries and key intersections.
bibliography
[1] Xu Guangqing. A preliminary study on the externalities of traffic congestion in Beijing and its government solutions[J].Progress in Geography,2006(4):129-136.)
[2] Huang Peibei, Liu Miaolong. Research on fractal characteristics of urban transportation network based on GIS[J].Journal of Tongji University(Engineering Science),2002(11):1370-1374.)
[3] Sun Youxin, Qian Yongsheng, Wang Chunlei. Regional Traffic Coordinated Control System for Urban Road Network Loop[C]//Annual Conference of the Asian Society of Transportation and Transportation and Symposium on "Transportation and Logistics". Dalian:China Communications and Transportation Association,2007(in Chinese).
[4] Wu Xiongtao, Jiang Xiaoqing, Liu Liu, et al. Smart City,2020,6(7):169-170.)
[5] Liu Qin, Xu Jianmin. Journal of Traffic and Transportation Engineering,2012,12(3):108-112
Disclaimer: We respect originality and also focus on sharing. Some of the content comes from the Internet, the copyright belongs to the original author, only for learning and reference, it is forbidden to use it for commercial purposes, if you inadvertently infringe on the intellectual property rights of any media, company, enterprise or individual, please contact to delete (email: [email protected]), and the content of this headline push only represents the author's point of view, and has nothing to do with the headline operator, the authenticity of the content please readers identify by themselves, this headline does not assume any responsibility.