Optimal coordination of variable speed limit to eliminate freeway wide moving jams

2014 ◽  
Vol 25 (09) ◽  
pp. 1450038 ◽  
Author(s):  
Yizhi Wang ◽  
Jianming Hu ◽  
Li Li ◽  
Yi Zhang
Keyword(s):  
Speed Limit ◽  
Variable Speed ◽  
Variable Speed Limit ◽  
Coordination Model ◽  
Traffic Conditions ◽  
Traffic Uncertainty ◽  
Three Phase ◽  
Ca Model ◽  
Optimal Coordination ◽  
Traffic Theory

Variable speed limit (VSL) is well-known for the ability to eliminate freeway wide moving jam (WMJ). Different VSL maneuvers have been proposed and proved to be useful theoretically or empirically. However, the coordination of VSL still needs to be analyzed in order to cater for different traffic conditions encountered on the roadway. In this paper, we execute a study on freeway VSL method based on the three-phase traffic theory and Cellular Automata (CA) based simulations. Results indicate that VSL is a promising method in solving freeway WMJs, but in some cases, it induces new congestions due to improper configurations and the stochastic feature of traffic flow. Therefore, in this paper, we propose an optimal coordination model of VSL including five main principles. The purpose of our model lies on two aspects, to ensure the elimination of WMJ and to avoid the emergence of new traffic jams. By analyzing the traffic dynamics, we first present several theoretical principles of VSL configuration with respect to the WMJ elimination. Second, we study the relation between VSL effectiveness and the traffic uncertainty through CA model-based simulations and some empirical principles are raised.

scholarly journals Enhancing Freeway Safety through Intervening in Traffic Flow Dynamics Based on Variable Speed Limit Control

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Jinming You ◽  
Shouen Fang ◽  
Lanfang Zhang ◽  
John Taplin ◽  
Jingqiu Guo
Keyword(s):  
Real Time ◽  
Traffic Flow ◽  
New Technologies ◽  
Flow Dynamics ◽  
Crash Risk ◽  
Speed Limit ◽  
Variable Speed ◽  
Variable Speed Limit ◽  
Traffic Conditions ◽  
Safety Research

New technologies and traffic data sources provide great potential to extend advanced strategies in freeway safety research. The High Definition Monitoring System (HDMS) data contribute comprehensive and precise individual vehicle information. This paper proposes an innovative Variable Speed Limit (VSL) based approach to manage crash risks by intervening in traffic flow dynamics on freeways using HDMS data. We first conducted an empirical analysis on real-time crash risk estimation using a binary logistic regression model. Then, intensive microscopic simulations based on AIMSUN were carried out to explore the effects of various intervention strategies with respect to a 3-lane freeway stretch in China. Different speed limits with distinct compliance rates under specified traffic conditions have been simulated. By taking into account the trade-off between safety benefits and delay in travel time, the speed limit strategies were optimized under various traffic conditions and the model with gradient feedback produces more satisfactory performance in controlling real-time crash risks. Last, the results were integrated into lane management strategies. This research can provide new ideas and methods to reveal the freeway crash risk evolution and active traffic management.

USING VARIABLE SPEED LIMITS TO ELIMINATE WIDE MOVING JAMS: A STUDY BASED ON THREE-PHASE TRAFFIC THEORY

2012 ◽  
Vol 23 (09) ◽  
pp. 1250060 ◽  
Author(s):  
YIZHI WANG ◽  
YI ZHANG ◽  
JIANMING HU ◽  
LI LI
Keyword(s):  
Traffic Flow ◽  
Control Strategies ◽  
Vehicle Speed ◽  
Variable Speed ◽  
Speed Limits ◽  
Congested Traffic ◽  
Three Phase ◽  
Variable Speed Limits ◽  
Ca Model ◽  
Traffic Theory

One frequently observed congested traffic flow pattern is wide moving jam (WMJ), in which the average vehicle speed is very low and the density is very high. In some recent studies, variable speed limits (VSL) were proposed as effective measures to eliminate or abate the influence of jam waves. However, in most of these studies, the stochastic features of driving behaviors and the resulting uncertainty of traffic flow dynamics were not fully considered. In this paper, we use cellular automaton (CA) model-based simulations to test the performances of different VSL control strategies and apply the three-phase traffic theory to further analyze the obtained results. Based on the simulation results, we got two novel findings. Firstly, we observed seven, instead of the previously assumed six, states of traffic flow in the evolution process of WMJ, when VSL were applied. Secondly and more importantly, we found that inappropriate speed limit may induce new WMJ and exaggerate congestions in two ways: one way corresponds to an F → J transition and the other corresponds to an F → S → J transition. Based on these findings, the appropriate lower bound of VSL was finally discussed in this paper.

scholarly journals The Multi-Station Based Variable Speed Limit Model for Realization on Urban Highway

Electronics ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 801 ◽  
Author(s):  
Soobin Jeon ◽  
Chongmyung Park ◽  
Dongmahn Seo
Keyword(s):  
Real Time ◽  
Transportation Systems ◽  
Traffic Information ◽  
Transport Systems ◽  
Speed Limit ◽  
Stability Assessment ◽  
Variable Speed ◽  
Variable Speed Limit ◽  
Traffic Conditions ◽  
Real Time Traffic

Intelligent transport systems (ITS) are a convergence of information technology and transportation systems as seen in the variable speed limit (VSL) system. Since the VSL system controls the speed limit according to the traffic conditions, it can improve the safety and efficiency of a transport network. Many researchers have studied the real-time VSL (RVSL) algorithm based on real-time traffic information from multiple stations recording traffic data. However, this method can suffer from inaccurate selection of the VSL start station (VSS), incorrect VSL calculations, and is unable to quickly react to the changing traffic conditions. Unstable VSL systems result in more congestion on freeways. In this study, an enhanced VSL algorithm (EVSL) is proposed to address the limitations of the existing RVSL algorithm. This selects preliminary VSL start stations (pVSS), which is expected to end congestion using acceleration and allocates final VSSs for each congestion interval using selected pVSS. This controls the vehicles that entered the congestion area based on the selected VSS. We used four metrics to evaluate the performance of the proposed VSL (VSS stability assessment, speed control stability assessment, travel time, and shockwave), which were all enhanced when compared to the standard RVSL algorithm. In addition, the EVSL algorithm showed stable VSL performance, which is critical for road safety.

Cycle-based variable speed limit methodology for improved freeway merging

2017 ◽  
Vol 11 (10) ◽  
pp. 632-640 ◽  
Author(s):  
Li Zhang ◽  
Lei Zhang ◽  
David K. Hale ◽  
Jia Hu ◽  
Zhitong Huang
Keyword(s):  
Speed Limit ◽  
Variable Speed ◽  
Variable Speed Limit

scholarly journals Variable Speed Limit and Ramp Metering for Mixed Traffic Flows: A Review and Open Questions

2021 ◽  
Vol 11 (6) ◽  
pp. 2574
Author(s):  
Filip Vrbanić ◽  
Edouard Ivanjko ◽  
Krešimir Kušić ◽  
Dino Čakija
Keyword(s):  
Traffic Control ◽  
Ramp Metering ◽  
Transport Infrastructure ◽  
Control Algorithms ◽  
Speed Limit ◽  
Mixed Traffic ◽  
Traffic Flows ◽  
Variable Speed ◽  
Variable Speed Limit ◽  
Traffic Demand

The trend of increasing traffic demand is causing congestion on existing urban roads, including urban motorways, resulting in a decrease in Level of Service (LoS) and safety, and an increase in fuel consumption. Lack of space and non-compliance with cities’ sustainable urban plans prevent the expansion of new transport infrastructure in some urban areas. To alleviate the aforementioned problems, appropriate solutions come from the domain of Intelligent Transportation Systems by implementing traffic control services. Those services include Variable Speed Limit (VSL) and Ramp Metering (RM) for urban motorways. VSL reduces the speed of incoming vehicles to a bottleneck area, and RM limits the inflow through on-ramps. In addition, with the increasing development of Autonomous Vehicles (AVs) and Connected AVs (CAVs), new opportunities for traffic control are emerging. VSL and RM can reduce traffic congestion on urban motorways, especially so in the case of mixed traffic flows where AVs and CAVs can fully comply with the control system output. Currently, there is no existing overview of control algorithms and applications for VSL and RM in mixed traffic flows. Therefore, we present a comprehensive survey of VSL and RM control algorithms including the most recent reinforcement learning-based approaches. Best practices for mixed traffic flow control are summarized and new viewpoints and future research directions are presented, including an overview of the currently open research questions.

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