The heavy-haul train (HHT) has large capacity and high efficiency, which represents the level of freight and makes the amelioration of control performance a trend in various countries. Improving the model reliability and increasing the anti-disturbance ability of the operation controller are two main ways to improve the operation control accuracy of HHTs. Herein, to describe the large nonlinear system more precisely, an interval type-2 fuzzy logic system (IT2FLS) is introduced to obtain a dynamic model. Then, a linear active disturbance rejection controller (LADRC) is designed to achieve precise operational control. In addition, the ‘bandwidth method’ is combined with the sparrow search algorithm (SSA) to solve the difficulty of controller parameters adjustment. Afterwards, the stability analysis of the closed-loop control system is given. The simulation experiments are conducted based on data collected from HXD1 locomotives driven by excellent drivers. Results show that the speed tracking error is no more than 0.5 km/h, and demonstrate that the proposed method significantly improves the operational performance of HHTs.
{"title":"Linear active disturbance rejection control of heavy-haul train operation based on an interval type-2 fuzzy logic system model","authors":"Yating Fu, Wenxuan Rao, Hui Yang","doi":"10.1093/tse/tdac037","DOIUrl":"https://doi.org/10.1093/tse/tdac037","url":null,"abstract":"\u0000 The heavy-haul train (HHT) has large capacity and high efficiency, which represents the level of freight and makes the amelioration of control performance a trend in various countries. Improving the model reliability and increasing the anti-disturbance ability of the operation controller are two main ways to improve the operation control accuracy of HHTs. Herein, to describe the large nonlinear system more precisely, an interval type-2 fuzzy logic system (IT2FLS) is introduced to obtain a dynamic model. Then, a linear active disturbance rejection controller (LADRC) is designed to achieve precise operational control. In addition, the ‘bandwidth method’ is combined with the sparrow search algorithm (SSA) to solve the difficulty of controller parameters adjustment. Afterwards, the stability analysis of the closed-loop control system is given. The simulation experiments are conducted based on data collected from HXD1 locomotives driven by excellent drivers. Results show that the speed tracking error is no more than 0.5 km/h, and demonstrate that the proposed method significantly improves the operational performance of HHTs.","PeriodicalId":52804,"journal":{"name":"Transportation Safety and Environment","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44148310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper focuses on the creation of a dynamic probabilistic model which simulates deterioration trends of a marine engine lubrication system. The approach is based on risk and the implementation is achieved through a dynamic Bayesian network (dBN). Risk can be useful for decision making, while dBNs are a powerful tool for risk modelling and prediction models. The model takes into account deterioration of engine components, oil degradation and the off-line condition monitoring technique of oil analysis, in the context of predictive maintenance. The paper aims to efficiently predict probability evolution for main engine lubrication failure and to decide upon the most beneficial schemes from a variety of lubrication oil analysis interval schemes by introducing monetary costs and producing the risk model. Real data and respective analysis, along with expert elicitation, are utilized for achieving model quantification, while the model is materialized through a code in the Matlab environment. Results from the probabilistic model show a realistic simulation for the system and indicate the obvious, that with more frequent oil analyses and respective maintenance or repairs, the probability of failure drops significantly. However, the results from the risk model highlight that the costs can redefine scheme suggestions, as they can correspond to low probabilities of failure but also to higher costs. A two-month interval scheme is suggested, in contrast to the most preferred practice among shipping companies of a three-month interval. The developed model is in general identified as a failure prediction tool focusing on marine engine lubrication failure.
{"title":"A combined risk-based and condition monitoring approach: developing a dynamic model for the case of marine engine lubrication","authors":"N. Ventikos, P. Sotiralis, Emmanouil Annetis","doi":"10.1093/tse/tdac020","DOIUrl":"https://doi.org/10.1093/tse/tdac020","url":null,"abstract":"\u0000 This paper focuses on the creation of a dynamic probabilistic model which simulates deterioration trends of a marine engine lubrication system. The approach is based on risk and the implementation is achieved through a dynamic Bayesian network (dBN). Risk can be useful for decision making, while dBNs are a powerful tool for risk modelling and prediction models. The model takes into account deterioration of engine components, oil degradation and the off-line condition monitoring technique of oil analysis, in the context of predictive maintenance. The paper aims to efficiently predict probability evolution for main engine lubrication failure and to decide upon the most beneficial schemes from a variety of lubrication oil analysis interval schemes by introducing monetary costs and producing the risk model. Real data and respective analysis, along with expert elicitation, are utilized for achieving model quantification, while the model is materialized through a code in the Matlab environment. Results from the probabilistic model show a realistic simulation for the system and indicate the obvious, that with more frequent oil analyses and respective maintenance or repairs, the probability of failure drops significantly. However, the results from the risk model highlight that the costs can redefine scheme suggestions, as they can correspond to low probabilities of failure but also to higher costs. A two-month interval scheme is suggested, in contrast to the most preferred practice among shipping companies of a three-month interval. The developed model is in general identified as a failure prediction tool focusing on marine engine lubrication failure.","PeriodicalId":52804,"journal":{"name":"Transportation Safety and Environment","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47916969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yang Song, Huibin Wang, Chao Guo, Sitong Pan, Yuehua Wu
A tunnel fire may cause great damage to people, vehicles, facilities and tunnel structures if it is not effectively controlled. Therefore, it is very important to clarify the smoke propagation characteristics and influencing factors that can help to accelerate the removal of fire smoke and reduce casualties and property losses. In order to study the influence of slope, curvature radius and ambient temperature on smoke propagation during the tunnel operation period, based on the high-temperature spiral tunnel in Midi village, Yunnan Province, the internal and external environmental parameters of the tunnel were measured on site and the numerical simulation model was established by using the simulation software FDS, and the control variable method was used to study the fire smoke propagation characteristics of the tunnel with different characteristics. The results show that: the influence of slope on smoke migration velocity is non-linear, the greater the slope is, the greater the change of smoke spreading speed is; the smaller the curvature radius is, the greater the obstruction to smoke migration is, and the slower the smoke migration speed is; high temperature speeds up the smoke exhaust rate in the tunnel but has less promotion of the fire smoke migration.
{"title":"Smoke propagation characteristics and influencing factors of high-temperature spiral tunnel fire","authors":"Yang Song, Huibin Wang, Chao Guo, Sitong Pan, Yuehua Wu","doi":"10.1093/tse/tdac025","DOIUrl":"https://doi.org/10.1093/tse/tdac025","url":null,"abstract":"\u0000 A tunnel fire may cause great damage to people, vehicles, facilities and tunnel structures if it is not effectively controlled. Therefore, it is very important to clarify the smoke propagation characteristics and influencing factors that can help to accelerate the removal of fire smoke and reduce casualties and property losses. In order to study the influence of slope, curvature radius and ambient temperature on smoke propagation during the tunnel operation period, based on the high-temperature spiral tunnel in Midi village, Yunnan Province, the internal and external environmental parameters of the tunnel were measured on site and the numerical simulation model was established by using the simulation software FDS, and the control variable method was used to study the fire smoke propagation characteristics of the tunnel with different characteristics. The results show that: the influence of slope on smoke migration velocity is non-linear, the greater the slope is, the greater the change of smoke spreading speed is; the smaller the curvature radius is, the greater the obstruction to smoke migration is, and the slower the smoke migration speed is; high temperature speeds up the smoke exhaust rate in the tunnel but has less promotion of the fire smoke migration.","PeriodicalId":52804,"journal":{"name":"Transportation Safety and Environment","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48443735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To improve the traffic safety of electric two-wheelers (ETW), China has promulgated ETW standardization policies. This policy requires local governments to take measures to guide the illegal ETWs out of use. Governments have implemented a depreciation subsidy scheme to encourage users to scrap illegal ETWs early. When designing the subsidy scheme, effectively improving the ETWs' traffic safety at the road network level while saving government expenses is essential for the sustainable implementation of the policy. This study proposes an optimization method for depreciation subsidy design incorporating traffic safety evaluation. Based on the policy scheme, this study formulates a risk assessment model for the ETW traffic network to characterize the effect of the subsidy on improving safety. Then, we use the bi-level programming approach to model the subsidy strategy design problem. The upper-level problem reflects the goal of policymakers to maximize safety improvement and minimize government expenses. The lower-level problem describes the route choices of ETW users. The optimal subsidy design under different safety-expense trade-offs is analysed based on the Nguyen and Dupuis network and a real network extracted from Changsha City in China. The results show that specific subsidy schemes effectively improve road safety without a large government spending. When the market price or service life of ETWs increases, the government spending on the same safety goal increases. The government should comprehensively consider the safety effect of financial expense and the situation of the local ETW market before selecting reasonable subsidy strategies.
{"title":"Optimization of depreciation subsidy policy strategies for electric two-wheelers for improving traffic safety","authors":"Xintong Li, Helai Huang, Chunyang Han, Guangming Xu, Jaeyoung Lee, Cheng Hu","doi":"10.1093/tse/tdac028","DOIUrl":"https://doi.org/10.1093/tse/tdac028","url":null,"abstract":"\u0000 To improve the traffic safety of electric two-wheelers (ETW), China has promulgated ETW standardization policies. This policy requires local governments to take measures to guide the illegal ETWs out of use. Governments have implemented a depreciation subsidy scheme to encourage users to scrap illegal ETWs early. When designing the subsidy scheme, effectively improving the ETWs' traffic safety at the road network level while saving government expenses is essential for the sustainable implementation of the policy. This study proposes an optimization method for depreciation subsidy design incorporating traffic safety evaluation. Based on the policy scheme, this study formulates a risk assessment model for the ETW traffic network to characterize the effect of the subsidy on improving safety. Then, we use the bi-level programming approach to model the subsidy strategy design problem. The upper-level problem reflects the goal of policymakers to maximize safety improvement and minimize government expenses. The lower-level problem describes the route choices of ETW users. The optimal subsidy design under different safety-expense trade-offs is analysed based on the Nguyen and Dupuis network and a real network extracted from Changsha City in China. The results show that specific subsidy schemes effectively improve road safety without a large government spending. When the market price or service life of ETWs increases, the government spending on the same safety goal increases. The government should comprehensively consider the safety effect of financial expense and the situation of the local ETW market before selecting reasonable subsidy strategies.","PeriodicalId":52804,"journal":{"name":"Transportation Safety and Environment","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43910573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fenling Feng, Junjie Jia, Ailan Liang, Chengguang Liu
The operation of the China Railway Express features numerous links across several regions and countries. Effectively controlling the risks involved in the operation of the China Railway Express is crucial for ensuring safety and efficiency and promoting the sustainable development of the China Railway Express. The Bayesian network-based risk-management model was built corresponding to the actual operation of the China Railway Express; the model used an advanced risk-management theory. The sensitivity analysis of risk factors and Bayesian network inference were realized using the expectation-maximization and clique-tree propagation algorithms. Using the risk-checklist method, 17 risk-related factors were analysed on 17 nodes of the Bayesian network from three perspectives—safety, efficiency and effectiveness—based on expert opinions and the actual operating conditions of the China Railway Express. Data from a sensitivity analysis and evidence inference of the Bayesian network model indicated that the sensitivity coefficients of nodes N01, N04, N07, N08 and N17 of the network were high. Moreover, the risk-occurrence probabilities for nodes N01, N04, N06, N07 and N09 were higher in the case of reverse inference. Our results revealed the crucial factors influencing the risk. The identified risk factors included the stability of the political environment in countries along the route, conditions of station infrastructures and the complexity of the process of changing rails and reloading. Further, risk-management suggestions were provided. By establishing a sound risk-management framework, reliable assessment and management could be realized in accordance with changes in the operating conditions of the China Railway Express.
{"title":"Bayesian network-based risk evaluation model for the operational requirements of the China Railway Express under the Belt and Road initiative","authors":"Fenling Feng, Junjie Jia, Ailan Liang, Chengguang Liu","doi":"10.1093/tse/tdac019","DOIUrl":"https://doi.org/10.1093/tse/tdac019","url":null,"abstract":"\u0000 The operation of the China Railway Express features numerous links across several regions and countries. Effectively controlling the risks involved in the operation of the China Railway Express is crucial for ensuring safety and efficiency and promoting the sustainable development of the China Railway Express. The Bayesian network-based risk-management model was built corresponding to the actual operation of the China Railway Express; the model used an advanced risk-management theory. The sensitivity analysis of risk factors and Bayesian network inference were realized using the expectation-maximization and clique-tree propagation algorithms. Using the risk-checklist method, 17 risk-related factors were analysed on 17 nodes of the Bayesian network from three perspectives—safety, efficiency and effectiveness—based on expert opinions and the actual operating conditions of the China Railway Express. Data from a sensitivity analysis and evidence inference of the Bayesian network model indicated that the sensitivity coefficients of nodes N01, N04, N07, N08 and N17 of the network were high. Moreover, the risk-occurrence probabilities for nodes N01, N04, N06, N07 and N09 were higher in the case of reverse inference. Our results revealed the crucial factors influencing the risk. The identified risk factors included the stability of the political environment in countries along the route, conditions of station infrastructures and the complexity of the process of changing rails and reloading. Further, risk-management suggestions were provided. By establishing a sound risk-management framework, reliable assessment and management could be realized in accordance with changes in the operating conditions of the China Railway Express.","PeriodicalId":52804,"journal":{"name":"Transportation Safety and Environment","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43435042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Critical wind speed can play an important guiding role in developing an initial train operation schedule and knowledge of it may prevent safety risks for a train. Hence, the efficient and accurate calculation of the critical wind speeds of trains is critical. This study addresses this topic and focuses on the influence of different methods on the calculation of the critical wind speed. The result reveals that the five-mass and three-mass methods can both be used to determine the critical wind speed of a train more quickly with acceptable accuracy, but these two methods overestimate the crosswind safety risk of the train. With the increase of the train's operating speed, the nonlinearity of the vehicle system is further enhanced. In particular, the influence of the rolling motion between the car body and the bogie is more prominent, and the results of the five-mass method and the multi-body simulation method tend to be the closest. Last but not least, the damping parameters and inertial forces ignored by the quasi-static method will effectively reduce the wind forces transmitted to the track, resulting in a smaller overturning coefficient and higher critical wind speed.
{"title":"Effect of assessment methods on the determination of the critical wind speeds of high-speed trains","authors":"Shiwei Yang, Rong Liu, Dongrun Liu","doi":"10.1093/tse/tdac029","DOIUrl":"https://doi.org/10.1093/tse/tdac029","url":null,"abstract":"\u0000 Critical wind speed can play an important guiding role in developing an initial train operation schedule and knowledge of it may prevent safety risks for a train. Hence, the efficient and accurate calculation of the critical wind speeds of trains is critical. This study addresses this topic and focuses on the influence of different methods on the calculation of the critical wind speed. The result reveals that the five-mass and three-mass methods can both be used to determine the critical wind speed of a train more quickly with acceptable accuracy, but these two methods overestimate the crosswind safety risk of the train. With the increase of the train's operating speed, the nonlinearity of the vehicle system is further enhanced. In particular, the influence of the rolling motion between the car body and the bogie is more prominent, and the results of the five-mass method and the multi-body simulation method tend to be the closest. Last but not least, the damping parameters and inertial forces ignored by the quasi-static method will effectively reduce the wind forces transmitted to the track, resulting in a smaller overturning coefficient and higher critical wind speed.","PeriodicalId":52804,"journal":{"name":"Transportation Safety and Environment","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49396375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The development of innovative, complex marine systems, such as autonomous ship concepts, has led to risk-based approaches in design and operation that provide safety level quantification and continuous risk assessment. The existing approaches to dynamic risk assessment mainly aim at updating accident probabilities for specific risk scenarios, based on knowledge of system operation and failure, as well as on past accident and failure information. However, for innovative marine systems that include complex interactions, our ability to identify anything that might go wrong is very limited, which may lead to unidentified risks, and failure data may not be available. This paper presents the foundations of a framework for dynamic risk assessment, which is equally applicable to manned and autonomous ships and mainly relies on information about the safe operational envelope and real-time information regarding deviations from safety. Inspiration is drawn from how the biological immune system identifies the risk of infection in a dynamic environment. The objective is to show the feasibility and benefits of our approach for quantifying the operational risk of marine systems. This paper provides the conceptual basis for developing ship specific applications and describes a process for dynamic risk assessment that is methodologically based on artificial immune systems. To demonstrate the implementation of our framework, we described, an illustrative example that involves a ship in a grounding scenario. The results show that the bio-inspired assessment process and risk description can reflect the changes of the risk level of a marine system.
{"title":"Risk dynamics for marine systems: towards a bio-inspired framework for dynamic risk assessment","authors":"N. Ventikos, K. Louzis","doi":"10.1093/tse/tdac018","DOIUrl":"https://doi.org/10.1093/tse/tdac018","url":null,"abstract":"\u0000 The development of innovative, complex marine systems, such as autonomous ship concepts, has led to risk-based approaches in design and operation that provide safety level quantification and continuous risk assessment. The existing approaches to dynamic risk assessment mainly aim at updating accident probabilities for specific risk scenarios, based on knowledge of system operation and failure, as well as on past accident and failure information. However, for innovative marine systems that include complex interactions, our ability to identify anything that might go wrong is very limited, which may lead to unidentified risks, and failure data may not be available. This paper presents the foundations of a framework for dynamic risk assessment, which is equally applicable to manned and autonomous ships and mainly relies on information about the safe operational envelope and real-time information regarding deviations from safety. Inspiration is drawn from how the biological immune system identifies the risk of infection in a dynamic environment. The objective is to show the feasibility and benefits of our approach for quantifying the operational risk of marine systems. This paper provides the conceptual basis for developing ship specific applications and describes a process for dynamic risk assessment that is methodologically based on artificial immune systems. To demonstrate the implementation of our framework, we described, an illustrative example that involves a ship in a grounding scenario. The results show that the bio-inspired assessment process and risk description can reflect the changes of the risk level of a marine system.","PeriodicalId":52804,"journal":{"name":"Transportation Safety and Environment","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48835366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study proposes a conflict-based traffic safety assessment method by associating conflict frequency and severity with short-term traffic characteristics. Instead of analysing historical crash data, this study employs microscopic trajectory data to quantify the relationship between conflict risk and traffic characteristics. The time-to-collision (TTC) index is used to detect conflicts, and a severity index (SI) is proposed on the basis of time-integrated TTC. With SI, the k-means algorithm is applied to classify the conflict severity level. Then the severity of regional conflict risk is split to three levels. Zero truncated Poisson regression and ordered logit regression methods are employed to estimate the effects of short-term traffic characteristics on conflict frequency and severity, respectively. Furthermore, the copula-based joint modelling method is applied to explore the potential non-linear dependency of conflict risk outcomes. A total of 18 copula models are tested to select the optimal ones. The HighD dataset from Germany is utilized to examine the proposed framework. Both between-lane and within-lane factors are considered. Results show that the correlations between traffic characteristics and conflict risk are significant, and the dependency of conflict outcomes varies among different severity levels. The difference of speed variation between lanes significantly influences the conflict frequency and severity simultaneously. Findings indicate that the proposed method is practicable to assess real-time traffic safety within a specific region by using short-term (30-second time interval) traffic characteristics. This study also contributes to develop targeted proactive safety strategies by evaluating road safety based on conflict risk, and considering different severity levels.
{"title":"Modeling conflict risk with real-time traffic data for road safety assessment: a copula-based joint approach","authors":"Yuping Hu, Ye Li, Chen Yuan, Helai Huang","doi":"10.1093/tse/tdac017","DOIUrl":"https://doi.org/10.1093/tse/tdac017","url":null,"abstract":"\u0000 This study proposes a conflict-based traffic safety assessment method by associating conflict frequency and severity with short-term traffic characteristics. Instead of analysing historical crash data, this study employs microscopic trajectory data to quantify the relationship between conflict risk and traffic characteristics. The time-to-collision (TTC) index is used to detect conflicts, and a severity index (SI) is proposed on the basis of time-integrated TTC. With SI, the k-means algorithm is applied to classify the conflict severity level. Then the severity of regional conflict risk is split to three levels. Zero truncated Poisson regression and ordered logit regression methods are employed to estimate the effects of short-term traffic characteristics on conflict frequency and severity, respectively. Furthermore, the copula-based joint modelling method is applied to explore the potential non-linear dependency of conflict risk outcomes. A total of 18 copula models are tested to select the optimal ones. The HighD dataset from Germany is utilized to examine the proposed framework. Both between-lane and within-lane factors are considered. Results show that the correlations between traffic characteristics and conflict risk are significant, and the dependency of conflict outcomes varies among different severity levels. The difference of speed variation between lanes significantly influences the conflict frequency and severity simultaneously. Findings indicate that the proposed method is practicable to assess real-time traffic safety within a specific region by using short-term (30-second time interval) traffic characteristics. This study also contributes to develop targeted proactive safety strategies by evaluating road safety based on conflict risk, and considering different severity levels.","PeriodicalId":52804,"journal":{"name":"Transportation Safety and Environment","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46966731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Equipped with high driving automation and advanced communication technologies, connected and autonomous vehicles (CAV) are expected to possess a shorter reaction time and a wider vision, which are promising to improve traffic safety and efficiency. However, little attention has been paid to the effect of connectivity and spatial distribution on the safety performance of mixed traffic flow. In this paper, we attempt to investigate the impact of CAV on traffic safety considering these factors. To this end, a car-following model for CAV is proposed first. Then, the cooperative driving strategy for CAVs is designed. Precisely, the feedback gains of the information are adjusted in real-time and are designed based on the derived stability criterion of the mixed traffic flow. Microscopic simulations of mixed traffic flow in traffic oscillation are designed and conducted to explore how the distribution and connectivity of CAV affect the safety performance of mixed traffic flow. Simulation results show that increasing the penetration rate of CAV is promising to shift the safety performance of mixed traffic flow. In addition, the safety performance of mixed traffic flow is related to the spatial distribution and communication range of CAV. Besides, increasing communication range does not inevitably improve the safety performance of mixed traffic flow when the penetration rate of CAV is low. Moreover, it is also found from the spatial–temporal trajectory of the mixed traffic flow that introducing CAV can mitigate the propagation of the stop-and-go wave and increase the throughput.
{"title":"Impact of connected and autonomous vehicles on traffic safety of mixed traffic flow: from the perspective of connectivity and spatial distribution","authors":"Jiakuan Dong, Jiangfeng Wang, Dongyu Luo","doi":"10.1093/tse/tdac021","DOIUrl":"https://doi.org/10.1093/tse/tdac021","url":null,"abstract":"\u0000 Equipped with high driving automation and advanced communication technologies, connected and autonomous vehicles (CAV) are expected to possess a shorter reaction time and a wider vision, which are promising to improve traffic safety and efficiency. However, little attention has been paid to the effect of connectivity and spatial distribution on the safety performance of mixed traffic flow. In this paper, we attempt to investigate the impact of CAV on traffic safety considering these factors. To this end, a car-following model for CAV is proposed first. Then, the cooperative driving strategy for CAVs is designed. Precisely, the feedback gains of the information are adjusted in real-time and are designed based on the derived stability criterion of the mixed traffic flow. Microscopic simulations of mixed traffic flow in traffic oscillation are designed and conducted to explore how the distribution and connectivity of CAV affect the safety performance of mixed traffic flow. Simulation results show that increasing the penetration rate of CAV is promising to shift the safety performance of mixed traffic flow. In addition, the safety performance of mixed traffic flow is related to the spatial distribution and communication range of CAV. Besides, increasing communication range does not inevitably improve the safety performance of mixed traffic flow when the penetration rate of CAV is low. Moreover, it is also found from the spatial–temporal trajectory of the mixed traffic flow that introducing CAV can mitigate the propagation of the stop-and-go wave and increase the throughput.","PeriodicalId":52804,"journal":{"name":"Transportation Safety and Environment","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43145905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shuying Wang, Pengfei Liu, Jiazheng Zhong, Zhunlin Ni, T. Qu
When earth pressure balance (EPB) shield tunnels are constructed through clayey ground, the soil adheres to the cutter, cutterhead and chamber bulkhead due to the high adhesion strength between the steel and the clay, thus clogging the shield. To investigate the influence of different factors on the adhesion strength, this study used montmorillonite, kaolin and mixtures of the two as test soils. The adhesion strength between the steel and clay is determined with a customized rotary shear apparatus. The results show that when the consistency index of the soil specimen is less than 1, the adhesion strength between the steel and clay increases with the consistency index. As the consistency index decreases, the effect of the normal pressure on the adhesion strength gradually weakened. As the contact angle of the shear plate increases, thus reducing the hydrophilicity, the adhesion strength decreases. When the soil specimens with different plasticity index values have the same consistency index value, the adhesion strengths are similar. The adhesion strength increases gradually with increasing surface roughness. Based on grey incidence analysis, the order of the factors affecting the adhesion strength is as follows: normal pressure > consistency index > contact angle > plasticity index ≈ surface roughness. The normal pressure, consistency index and contact angle all have important effects on the adhesion strength between steel and clay. However, because there are no large differences in the contact angle among the metal materials, the approximate adhesion strength can be calculated by considering the effects of only the normal pressure and consistency index. The measures that are effective for preventing EPB shield clogging are increasing the soil softness and decreasing the hydrophilicity of the cutterhead by applying new materials for the cutters and cutterhead.
{"title":"Influence factors and calculation model of the adhesion strength of clayey soil for EPB shield tunnelling","authors":"Shuying Wang, Pengfei Liu, Jiazheng Zhong, Zhunlin Ni, T. Qu","doi":"10.1093/tse/tdac012","DOIUrl":"https://doi.org/10.1093/tse/tdac012","url":null,"abstract":"\u0000 When earth pressure balance (EPB) shield tunnels are constructed through clayey ground, the soil adheres to the cutter, cutterhead and chamber bulkhead due to the high adhesion strength between the steel and the clay, thus clogging the shield. To investigate the influence of different factors on the adhesion strength, this study used montmorillonite, kaolin and mixtures of the two as test soils. The adhesion strength between the steel and clay is determined with a customized rotary shear apparatus. The results show that when the consistency index of the soil specimen is less than 1, the adhesion strength between the steel and clay increases with the consistency index. As the consistency index decreases, the effect of the normal pressure on the adhesion strength gradually weakened. As the contact angle of the shear plate increases, thus reducing the hydrophilicity, the adhesion strength decreases. When the soil specimens with different plasticity index values have the same consistency index value, the adhesion strengths are similar. The adhesion strength increases gradually with increasing surface roughness. Based on grey incidence analysis, the order of the factors affecting the adhesion strength is as follows: normal pressure > consistency index > contact angle > plasticity index ≈ surface roughness. The normal pressure, consistency index and contact angle all have important effects on the adhesion strength between steel and clay. However, because there are no large differences in the contact angle among the metal materials, the approximate adhesion strength can be calculated by considering the effects of only the normal pressure and consistency index. The measures that are effective for preventing EPB shield clogging are increasing the soil softness and decreasing the hydrophilicity of the cutterhead by applying new materials for the cutters and cutterhead.","PeriodicalId":52804,"journal":{"name":"Transportation Safety and Environment","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41625343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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