This research proposes a numerical methodology to assess the behavior of a car towing a generic caravan in crosswind conditions. Driving with crosswind can lead to dangerous situations. The vehicle can have stability issues and eventually crash. Different crosswind and vehicle velocities have been analysed using a car-caravan dynamic model with accurate aerodynamic loads. The forces generated by the action of the wind are calculated with CFD simulations and applied to the vehicle to perform dynamic simulations. Results show that also non-extreme crosswind condition could lead to dangerous situations.
For obstacle avoidance against randomly moving traffic participants, stochastic model predictive control is promising. In crowded environments, however, feasible trajectories satisfying chance constraints do not necessarily exist; crowding induces a relaxation of constraints that causes deterioration of safety. To address this issue, we developed a velocity control method that decelerates the ego vehicle to a speed that satisfies the chance constraints on the prediction horizon. We conducted numerical simulations of obstacle avoidance and experiments of moving through a crowd comprising vehicles and pedestrians to evaluate the performance. The results indicate that the designed controller can generate a trajectory that mitigates the relaxation of constraints and adapts to various traffic participants.
In Japan, the guidelines of safety technology for automated vehicles clearly state the requirement of level-3 equipment with minimal risk maneuver (MRM) in automated vehicles. In case the drivers fail to respond to a request for intervention, the conditional driving automation system activates an MRM to control the vehicle to a halt in the driving lane or on the side of the road. The current study aims to explore the research question: how does the information of the MRM functionality equipped within the automated vehicle affect the driver behavior during conditionally automated driving? In this study, we hypothesized that drivers who are provided with information about MRM functionality may reduce their attention toward the surrounding environment. The attention allocation to the surrounding environment may be related to the quality of take-over performance. Therefore, we attempted to observe the drivers’ takeover performance in response to RtI. Accordingly, a driving simulator experiment was conducted with 28 drivers as participants to investigate the influence of information regarding MRM on driver behavior. Two groups were formed by randomly placing the participants with and without providing MRM information. The results revealed that the information on MRM triggered a behavioral change in the drivers and reduced their attention toward the surrounding environment or allocated more attention toward the surrounding environment. In future, we would examine the method and content of communicating the MRM information to drivers using automated driving systems.
Traffic congestion on highways is a social issue that requires immediate resolution as it is a cause of economic loss, environmental problems, as well as traffic accidents. The objective of this research is to help resolve the issue of traffic congestion using connected vehicle and automated driving technologies, which have continued to make remarkable progress in recent years. This paper proposes a lane change control system and an optimization-based control algorithm running on a cloud server to rectify traffic flows. The effects of these proposals on reducing congestion at the Kashima interchange merging zone on the Hanshin Expressway was investigated using a traffic simulation with actual traffic data. This paper also studies the effects of communication delays between vehicles and the cloud server.
ABSTRACT: Road accidents have been caused by many factors and finding the root cause is very important. In previous report, logistic regression analysis method was used to identify high-risk accident factors. It was possible to analyze the significant factors, but the method alone cannot identify the causal chain and root cause of accidents. This paper presents an analysis of 86,331 traffic accident (TA) data in Nagano prefecture, where eight accident factors with odds ratio ≥ 3 considered to cause high-risk accidents were applied to build Bayesian Network (BN)s. The aim of this study is to study the method of extracting high-risk accident causes in Nagano using Bayesian Network analysis. As a result, 37 BN causal chains were obtained with all sequence orders lead to high-risk accidents, which caused serious injuries or deaths in Nagano. The results also confirmed that the highest-risk accident in Nagano to be single-vehicle collision accidents happened due to law violation such as over speeding at intersection and the high impact causing severe injury or death. Using information obtained through BN analysis, more focus on high-risk accidents with typical characteristics in Nagano can be given and countermeasures can be constructed for cases that needed more attention with logical and reasonable approach.
ABSTRACT: The objective of this study is to improve fatigue life of T-shape arc welded joint structures which are often used in automobiles. In conventional T-shape joint, ST-joint (Standard T-joint), a vertical part is welded to a flat surface in the horizontal part. In this paper, a new structure, CCT-joint (Concave shape T-joint), is proposed which can reduce stresses around a joint line in car driving. In a CCT-joint, a vertical part is welded to a concave surface in the horizontal part. Fatigue life of a CCT-joint was significantly longer than that of a conventional ST-joint. Results of this study suggest that the drastic improvement in fatigue life was due to stress reduction by the concave shape around the joint line. FEM stress analysis revealed that the maximum stress near the weld line of CCT-joint was reduced to less than half that of the ST-joint. Furthermore, it was found that the locations of the maximum stress were different between the CCT-joint and the ST-joint. This suggests that the crack origin positions of both joints are different, which was also confirmed experimentally. The geometry, hardness, and residual stresses after welding were investigated around the weld toe. The effects of geometry and hardness were small on the fatigue life. The residual stresses were decreased by CCT-joint. The evaluation of the advantage of residual stress reduction by CCT-joint compared with that of stress reduction in car driving will be investigated and discussed in the next step of this study.