scholarly journals Evaluating the Safety Impact of Connected and Autonomous Vehicles with Lane Management on Freeway Crash Hotspots Using the Surrogate Safety Assessment Model

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Hui Zhang ◽  
Ninghao Hou ◽  
Jianhua Zhang ◽  
Xuyi Li ◽  
Yan Huang
Keyword(s):  
Traffic Safety ◽  
Autonomous Vehicles ◽  
Safety Assessment ◽  
Assessment Model ◽  
Trajectory Data ◽  
Collision Risk ◽  
Velocity Difference ◽  
Safety Benefit ◽  
Crash Hotspots ◽  
The Impact

One goal for large-scale deployment of connected and autonomous vehicles is to achieve the traffic safety benefit since connected and autonomous vehicles (CAVs) could reduce the collision risk by enhancing the driver’s situation perception ability. Previous studies have analyzed the safety impact of CAVs involved in traffic, but only few studies examined the safety benefits brought by CAVs when approaching high-collision-risk road segments such as the freeway crash hotspots. This study chooses one freeway crash hotspot in Wuhan, China, as an instance and attempts to estimate the safety benefits for differential penetration rates (PRs) of CAVs using the surrogate safety assessment model (SSAM). First, the freeway crash hotspot is identified with kernel density estimation and simulated by VISSIM. Then, the intelligent driver model (IDM) and Wiedemann 99 (a car-following model) are adopted and calibrated to control the driving behaviors of CAVs and human-driven vehicles (HVs) in this study, respectively. The impact that rather CAVs are constrained with or without managed lanes on traffic safety is also discussed, and the PR of CAVs is set from 10% to 90%. The results of this study show that when the PR of CAVs is lower than 50%, there is no significant improvement on the safety measures such as conflicts, acceleration, and velocity difference, which are extracted from the vehicle trajectory data using SSAM. When the penetration rate is over 70%, the experiment results demonstrate that the traffic flow passing the freeway hotspot is with fewer conflicts, smaller acceleration, and smaller velocity difference in the scenario where CAVs are constrained with managed lane compared with the scenario without managed lane control. The safety benefit that CAVs bring needs to be discussed. The lane management of CAVs will also lead to distinct safety impact.

Longitudinal Collision Risk Assessment of Paired Departure to Closed Spaced Parallel Runways

2014 ◽  
Vol 1030-1032 ◽  
pp. 2028-2033
Author(s):  
Zhao Ning Zhang ◽  
Hui Qiao ◽  
Ting Ting Lu
Keyword(s):  
Risk Assessment ◽  
Traffic Control ◽  
Air Traffic Control ◽  
Safety Assessment ◽  
Error Distribution ◽  
Air Traffic ◽  
Assessment Model ◽  
Collision Risk ◽  
Safety Operation ◽  
Calculation Models

Paired departure to closed spaced parallel runways can effectively improve capacity of terminal, and also can solve congestion of busy airport, but it also increases the complexity of air traffic control .For ensuring safety operation of paired departure, the longitudinal collision risk of paired departure to closed spaced parallel runways was studied. Based on the acceleration error distribution and requirements on wake avoidance during paired departure, a longitudinal collision risk safety assessment model of closed spaced parallel runways paired departure was built. The parameters in this model were determined by providing the calculation models. In the end, an example was calculated to verify the model, and it turns out that this model is feasible.

scholarly journals Estimating and Comparing Response Times in Traditional and Connected Environments

2019 ◽  
Vol 2673 (4) ◽  
pp. 674-684 ◽  
Author(s):  
Anshuman Sharma ◽  
Zuduo Zheng ◽  
Jiwon Kim ◽  
Ashish Bhaskar ◽  
Md. Mazharul Haque
Keyword(s):  
Decision Making ◽  
Traffic Safety ◽  
Driving Simulator ◽  
Response Times ◽  
Flow Characteristics ◽  
Trajectory Data ◽  
Stimulus Response ◽  
Wide Range ◽  
The Mean ◽  
The Impact

Response time (RT) is a critical human factor that influences traffic flow characteristics and traffic safety, and is governed by drivers’ decision-making behavior. Unlike the traditional environment (TE), the connected environment (CE) provides information assistance to drivers. This in-vehicle informed environment can influence drivers’ decision-making and thereby their RTs. Therefore, to ascertain the impact of CE on RT, this study develops RT estimation methodologies for TE (RTEM-TE) and CE (RTEM-CE), using vehicle trajectory data. Because of the intra-lingual inconsistency among traffic engineers, modelers, and psychologists in the usage of the term RT, this study also provides a ubiquitous definition of RT that can be used in a wide range of applications. Both RTEM-TE and RTEM-CE are built on the fundamental stimulus–response relationship, and they utilize the wavelet-based energy distribution of time series of speeds to detect the stimulus–response points. These methodologies are rigorously examined for their efficiency and accuracy using noise-free and noisy synthetic data, and driving simulator data. Analysis results demonstrate the excellent performance of both the methodologies. Moreover, the analysis shows that the mean RT in CE is longer than the mean RT in TE.

scholarly journals Studying the Simultaneous Effect of Autonomous Vehicles and Distracted Driving on Safety at Unsignalized Intersections

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Mohammad Khashayarfard ◽  
Habibollah Nassiri
Keyword(s):  
Intelligent Transportation Systems ◽  
Autonomous Vehicles ◽  
Safety Assessment ◽  
Human Error ◽  
Transportation Systems ◽  
Text Messages ◽  
Assessment Model ◽  
Driving Simulators ◽  
Time To Collision ◽  
Unsignalized Intersections

Human error is one of the leading causes of accidents. Distraction, fatigue, poor visibility, speeding, and other such errors made by drivers can cause accidents. With the rapid advancements in automation technologies, transportation planners have strived to use Intelligent Transportation Systems (ITS) to minimize human error. In this study, the effect of Autonomous Vehicles (AVs) on the number of potential conflicts at two unsignalized intersections is investigated by using a microsimulation model in PTV Vissim software. For human-driven cars, the factor that is considered for calibration is driver distraction mainly caused by reading or writing text messages on a cellphone while driving. This factor can be estimated using driving simulators. In this paper, five different scenarios were defined for simulation, in addition to the primary state, according to the different market penetration rates of AVs in Vissim. Safety assessment was performed by the Surrogate Safety Assessment Model (SSAM) using Time to Collision (TTC) and Deceleration Rate to Avoid Crashes (DRAC) indicators to determine the number of accidents. It was concluded that the presence of 100% of AVs could reduce the potential for accidents by up to 93%.

Operational safety of automated and human driving in mixed traffic environments: A perspective of car-following behavior

2021 ◽  
pp. 1748006X2110506
Author(s):  
Tao Li ◽  
Xu Han ◽  
Jiaqi Ma ◽  
Marilia Ramos ◽  
Changju Lee
Keyword(s):  
Traffic Safety ◽  
Risk Mitigation ◽  
Safety Evaluation ◽  
Mixed Traffic ◽  
Trajectory Data ◽  
Road Transportation ◽  
Baseline Model ◽  
Car Following ◽  
On The Road ◽  
The Impact

The advent of automated vehicles (AVs) will provide opportunities for safer, smoother, and smarter road transportation. During the transition from the current human-driven vehicle (HV) to a fully AV traffic environment, there will be a mixed traffic flow including both HVs and AVs. The impact of introducing AVs into existing traffic, however, has not yet been fully understood. In this paper, we advance this understanding by conducting mixed traffic safety evaluation from the perspective of car-following behavior using real-world AV operational data of mixed traffic. To understand how the AVs impact other vehicles on the road, we analyzed the operational behaviors of HV-following-HV, AV-following-HV, and HV-following-AV. A selected car-following model is calibrated, and results show that there are significant differences between the HV-following-HV and the other two groups, indicating safe AV behavior and changes in HV behavior (i.e. less aggressive, safer) after the introduction of AVs into the traffic. Additionally, to understand AV behavioral safety, we investigate behavior predictions (one of the most critical inputs for AVs to make car-following decisions) of AVs and their surrounding vehicles using a mature baseline model and a new Conditional Variational Autoencoder (CVAE) framework. The result shows potential risks of inaccurate predictions of the baseline model and the necessity to consider additional factors, such as vehicle interactions and driver behavior, into the prediction for risk mitigation. Arterial vehicle trajectory data from the Lyft Level 5 Dataset is applied to test the proposed methodological framework to understand the car-following safety risks of HVs and AVs in the mixed traffic stream.

scholarly journals Ground Risk Assessment of UAV Operations Based on Horizontal Distance Estimation under Uncertain Conditions

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yang Liu ◽  
Xuejun Zhang ◽  
Zhi Wang ◽  
Ziang Gao ◽  
Chang Liu
Keyword(s):  
Drag Force ◽  
Safety Assessment ◽  
Local Population ◽  
Assessment Model ◽  
Flying Height ◽  
Weather Data ◽  
Horizontal Distance ◽  
Proposed Model ◽  
Failure Point ◽  
The Impact

In this paper a ground safety assessment model is introduced based on the probability estimation of possible impact positions when unmanned aerial vehicle (UAV) crashes on the ground. By incorporating the random uncertainties during the descending process, risks associated with UAV’s ground crash are estimated accurately. The number of victims on the ground per flight hour is selected as the indicative index to evaluate the risk levels of the corresponding ground area. We mainly focus on the analysis of uncertainties that usually appear in drag coefficient which would generate a great amount of effects on the travelled horizontal distance from the failure point to the impact point on the ground, which further influences the possible impact positions. The drag force in the air, failure velocity of a UAV, and wind effects in the local area are all considered in the proposed model, as well as ground features, including sheltering effects on the ground, UAV parameter settings, and distribution of local population. Uncertainties in drag force when a UAV descends, UAV’s initial horizontal and vertical speeds at failure point, and local wind patterns are all considered as the indispensable factors in the proposed model. Especially the probability of fatality once hit by the UAV’s debris is explored to make the safety assessment more reliable and valuable. In the end, the actual UAV parameters and official historical weather data are used to estimate the risks in a real operation environment when a failure event happens at a legal flying height. Experimental results are given based on different types of UAVs and random effects in the descent. The results show that all the operations of all kinds of UAVs selected in the validation are so dangerous that the safety of people on the ground cannot be guaranteed, whose value is much bigger than the manned aircraft safety criterion 10−7.

scholarly journals Safety Evaluation of Turbo-Roundabouts with and without Internal Traffic Separations Considering Autonomous Vehicles Operation

2021 ◽  
Vol 13 (16) ◽  
pp. 8810
Author(s):  
Tullio Giuffrè ◽  
Anna Granà ◽  
Salvatore Trubia
Keyword(s):  
Autonomous Vehicles ◽  
Safety Assessment ◽  
Safety Evaluation ◽  
Simulation Models ◽  
Safety Performance ◽  
Assessment Model ◽  
Crash Data ◽  
Vehicle Trajectories ◽  
Traffic Conflicts ◽  
Surrogate Measures

The paper presents a microsimulation approach for assessing the safety performance of turbo-roundabouts where Cooperative Autonomous Vehicles “CAVs” have been introduced into the traffic mix alongside conventional vehicles “CVs”. Based on the analysis of vehicle trajectories from VISSIM and subsequent analysis of traffic conflicts through the Surrogate Safety Assessment Model (SSAM), the research aims to evaluate the safety benefits of turbo-roundabouts where the lanes are physically separated by raised curbs, compared to roundabouts without such curbs. The paper will then describe the methodological path followed to build VISSIM models of turbo-roundabouts with and without raised curbs in order to calibrate the simulation models and estimate the potential conflicts when a higher percentage of CAVs are introduced into the traffic mix. A criterion has been also proposed for setting properly the principal SSAM filters. The results confirmed both higher safety levels for turbo-roundabouts equipped with raised lane dividers compared to turbo-roundabout solutions without curbs, and better safety conditions under the traffic mix of CVs and CAVs. Therefore, it follows that, in absence of crash data including CAVs, the surrogate measures of safety are the only approach in which the safety performance of any roundabout or road entity can be evaluated.

Implementation of Active Traffic Management Strategies for Safety on Congested Expressway Weaving Segments

2017 ◽  
Vol 2635 (1) ◽  
pp. 28-35 ◽  
Author(s):  
Ling Wang ◽  
Mohamed Abdel-Aty ◽  
Jaeyoung Lee
Keyword(s):  
Traffic Safety ◽  
Traffic Management ◽  
Management Strategies ◽  
Ramp Metering ◽  
Assessment Model ◽  
Variable Speed ◽  
Analysis Model ◽  
Variable Speed Limit ◽  
Average Travel Time ◽  
The Impact

In weaving segments, traffic merges, diverges, and weaves in a limited space. These traffic maneuvers might result in high crash hazards. To improve the safety of a congested expressway weaving segment, this study tested various active traffic management (ATM) strategies in microsimulations. Crash odds and the Surrogate Safety Assessment Model were used to evaluate the impact of ATM strategies on traffic safety. The crash odds were calculated based on the real-time safety analysis model for weaving segments. The strategies included ramp metering (RM), variable speed limit (VSL), and integrated RM and VSL (RM-VSL). Overall, the results showed that the ATM strategies improved the safety of the studied weaving segment. The modified ALINEA RM algorithms, which took lane occupancy and safety into consideration, outperformed the traditional ALINEA algorithm from a safety perspective. The 45 mph VSLs, which were located at the upstream of the studied weaving segment, significantly enhanced safety without notably increasing average travel time. A consolidated RM-VSL strategy was also proposed with the aim of improving traffic safety by implementing RM and VSL. In the consolidated RM-VSL strategy, the modified ALINEA RM was adjusted according to the queue length to prevent long queues on ramps. The results proved that the consolidated RM-VSL strategy reduced the number of conflicts by 16.8% and decreased the crash odds by 6.0%.

scholarly journals Traffic Risk Modelling and Analysis under Airport-Like Simulation Environment

2022 ◽  
Vol 2022 ◽  
pp. 1-10
Author(s):  
Yanting Sheng ◽  
Rui Feng ◽  
Salvatore Antonio Biancardo
Keyword(s):  
Traffic Safety ◽  
Autonomous Vehicles ◽  
Autonomous Vehicle ◽  
Vehicle Safety ◽  
Collision Risk ◽  
Risk Modelling ◽  
Time To Collision ◽  
Additional Information ◽  
Traffic Conditions ◽  
Research Findings

Traffic safety plays a crucial role in the development of autonomous vehicles which attracts significant attention in the community. It is a challenge task to ensure autonomous vehicle safety under varied traffic environment interference, especially for airport-like closed-loop conditions. To that aim, we analyze autonomous vehicle safety at typical roadway conditions and traffic state constraints (e.g., car-following state at different speed distributions) by simulating the airport-like traffic conditions. The experimental results suggest that traffic collision risk is in a positive relationship with the speed difference and distance among adjacent vehicles. More specifically, the autonomous vehicle may collide with neighbors when the time to collision (TTC) indicator is lower than 4 s, and vice versa. The research findings can help both research community and practioners obtain additional information for improving traffic safety for autonomous vehicles.

scholarly journals Case study of a water bioengineering construction site in Austria. Ecological aspects and application of an environmental life cycle assessment model

2021 ◽  
Author(s):  
M. von der Thannen ◽  
S. Hoerbinger ◽  
C. Muellebner ◽  
H. Biber ◽  
H. P. Rauch
Keyword(s):  
Global Warming ◽  
Life Cycle Assessment ◽  
Life Cycle ◽  
Energy Demand ◽  
Assessment Model ◽  
Construction Site ◽  
Negative Effects ◽  
Environmental Life Cycle Assessment ◽  
The Impact ◽  
Soil And Water

AbstractRecently, applications of soil and water bioengineering constructions using living plants and supplementary materials have become increasingly popular. Besides technical effects, soil and water bioengineering has the advantage of additionally taking into consideration ecological values and the values of landscape aesthetics. When implementing soil and water bioengineering structures, suitable plants must be selected, and the structures must be given a dimension taking into account potential impact loads. A consideration of energy flows and the potential negative impact of construction in terms of energy and greenhouse gas balance has been neglected until now. The current study closes this gap of knowledge by introducing a method for detecting the possible negative effects of installing soil and water bioengineering measures. For this purpose, an environmental life cycle assessment model has been applied. The impact categories global warming potential and cumulative energy demand are used in this paper to describe the type of impacts which a bioengineering construction site causes. Additionally, the water bioengineering measure is contrasted with a conventional civil engineering structure. The results determine that the bioengineering alternative performs slightly better, in terms of energy demand and global warming potential, than the conventional measure. The most relevant factor is shown to be the impact of the running machines at the water bioengineering construction site. Finally, an integral ecological assessment model for applications of soil and water bioengineering structures should point out the potential negative effects caused during installation and, furthermore, integrate the assessment of potential positive effects due to the development of living plants in the use stage of the structures.

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