01 A Cooperative Map Matching Algorithm Applied in Intelligent and Connected Vehicle Positioning
02 Indoor Sign-based Visual Localization Method
03 Intelligent Vehicles Localization Based on Semantic Map Representation from 3D Point Clouds
04 Companion Relationship Discovering Algorithm for Passengers in the Cruise Based on UWB Positioning
05 An Overview of Traffic Management in "Automatic+Manual" Driving Environment
06 An Image Generation Method for Automated Driving Based on Improved GAN
07 An Analysis of Injury Severities in School Bus Accidents Based on Random Parameter Logit Models
Aircraft scheduling is a key link in flight planning, directly affecting the safety and economic efficiency of civil aviation transport. With the expansion of the aircraft fleet in China, research on large-scale aircraft scheduling problems (ASP) has become urgent. However, the fleet assignment model and aircraft scheduling models (ASMs) with different decision-making objectives (e.g., operational profitability, maintenance requirements, and robustness) cannot meet the needs since the number of constraints and the scale of the problem are often limited. By analyzing the connections and limitations of the existing ASMs, this paper summarizes the model and its solution algorithms for large-scale integrated ASP, analyzes the scope of application, advantages and disadvantages of each algorithm, and finds that: the phased scheduling model cannot guarantee the global optimal solution, while the integrated aircraft scheduling model is more practical; the exact algorithm can theoretically guarantee the optimal solution, but it is complicated, time-consuming, and difficult to decompose; the heuristic algorithm is fast and simple, but quality of the solution and the stability of the algorithm cannot guaranteed. Lastly, further research directions for large-scale integrated ASP are concluded: ① In terms of problem modelling, an integrated scheduling model can be established to optimize the route network structure and overcome the limitations of the existing models by taking into account factors such as route demand, time-balanced scheduling, and personalized crew assignments; ② In terms of problem-solving, Benders decomposition and column generation algorithms can be combined to decompose the whole problem into relatively simple main problems and sub-problems, reducing the difficulty of solving; additionally, the exact algorithms and heuristic algorithms can be combined to reduce the computational time and guarantee the accuracy of the solution, improving the solution efficiency.
Focusing on urban UAVs route flight, in order to ensure the safety of operation, it is necessary to equip the UAVs with appropriate separation. For the longitudinal flight scenario of the same route, a separation regulation model that considers the conflict frequency and collision probability and complies with the ICAO separation principle is investigated. By considering only the collision risk of UAVs positioning error, the longitudinal separation is obtained, which is used as the benchmark for the subsequent separation calculation. By considering the position uncertainty caused by both positioning error and velocity error, the collision risk along with the flight progress of UAVs is calculated. Increasing the longitudinal separation will delay the time to break through the target level of safety, but as the flight progresses, the collision risk will eventually overstep the target level of safety. Based on this finding, the method of UAV position regulation mechanism is proposed, and the distance between two aircraft is calibrated periodically. For a given target level of safety, a curve of longitudinal separation and position control frequency can be obtained, and a game relationship is found to exist between them. Implementation of high-frequency control, a smaller route separation is needed. Otherwise, the required route separation should be increased. In order to take into account, the double constraints of urban airspace and position control ability, a compromise scheme to select the separation and the control frequency at the maximum curvature is presented. It is found that the more stringent the safety target level requirements, the greater the required frequency of regulation and flight separation. The experimental analysis finds that when the target level of safety is 5×10-9 times/flight hour, the required control frequency is 87 times/hour and the required longitudinal separation is 90 m. At the same time, in the actual operating environment, the application of the above evaluation models and methods can objectively select the required separation and regulation frequency. The research in this paper can consider the safety of urban logistics UAV air operation and improve urban airspace utilization and delivery efficiency.
The multi-rotor electric vertical take-off and landing vehicle (eVTOL) is a future vehicle, that has been a research hotspot in recent years. However, the limited accuracy of vertical positioning and potential dangers of crossing flight hamper the establishment of the operational separation standard (OSS) for eVTOL, which makes it far from the application in practice. To explore the OSS for eVTOL, the shape of the eVTOL is considered, which is wider at the bottom and taper at the top, an improved Event-based vertical collision model is developed, and the safety evaluation method for eVTOL is proposed based on the improved model. The proposed method considers the main characteristics of eVTOL such as the shape, navigation accuracy, operation feature, positioning error, flight speed, speed error, etc., uses a conical frustum collision box instead of the cuboid box in the original model, and introduces relative speed, probability of lateral overlap and probability of vertical overlap as the parameters in safety evaluation method, capturing the characteristics of the eVTOL, reducing the computational redundancy, and enhancing the accuracy of the collision model. To demonstrate the proposed model and method, the multi-rotor eVTOL EHang 216-S is taken as an example, and the vertical separation minimum (VSM) under different target levels of safety (TLS) and navigation accuracy are calculated. The results show that: ① the reduction of the TLS and the navigation accuracy will lead to the reduction of the VSM. ② When the TLS is set as 1×10-6 times/flight hour and the navigation accuracy is set as required navigation performance of 10 (RNP10), VSM can be reduced to 11 meters. ③ When the navigation accuracy is RNP10 and the VSM is 11 meters, the calculated collision risk by the proposed method will be lower than the original method by 24.78%. It indicates that the introduction of the conical frustum collision box in the safety evaluation for eVTOL would result in a more accurate and reasonable calculation of collision risk than the original method, providing theoretical support for the establishment of vertical separation standards for eVTOL.
Interchange bridges serve as important nodes in road traffic networks, facilitating the redirection of traffic flows in different directions. Currently, high-density interchanges are increasingly common in urban road networks. With closer spacing of high-density interchanges compared to regular ones, denser vehicle weaving occurs and drivers are required to perform merging and diverging maneuvers in a shorter time. To investigate the impact of interchange spacing on drivers' mental load and the corresponding statistical characteristics in the entrances and exits of high-density interchanges, a segment of the Inner Ring Expressway in Chongqing with four consecutive interchanges, three of which are high-density interchanges, was selected as the research site. Electrocardiogram data from 47 drivers during on-road experiments were collected using in-vehicle instruments. Differential analysis was conducted on the temporal and spectral indices of driver heart rate variability between the entrances and exits of high-density and regular-spacing interchanges, revealing the distributions of drivers' mental load in these sections. The results indicate that: There is no significant difference in the temporal index of heart rate variability between drivers passing through the entrances and exits of regular-spacing and high-density interchanges. However, there is a significant difference in the spectral index, i.e., the ratio of low-frequency to high-frequency power of heart rate variability (LF/HF), which is believed can serve as the main indicator for evaluating drivers' mental load in interchange entrances and exits. When passing through the entrances of high-density interchanges, the LF/HF significantly increased compared to the one when passing through the entrances of regular-spacing interchanges, indicating that insufficient interchange spacing would increase mental load in the entrances of interchanges. Conversely, the LF/HF is significantly higher when passing through the exits of regular-spacing interchanges than the one when passing through the exits of high-density interchanges, indicating greater mental load when passing through exits of regular-spacing interchanges. For high-density interchanges, drivers' mental load in entrances are slightly higher than that in exits.
Taking a certain light rail line as the basis, a low-floor trams vehicle-track coupled dynamic model is established utilizing the multi-body dynamics software Universal Mechanism (UM). LM wear-type treads and R50 standard rails are selected, and the US VI irregularity track spectrum is used as the line excitation. Firstly, the vehicle's dynamic response and wheel wear is studied under five different friction coefficients, based on Hertz and simplified Kalker theories, as well as the Archard model. Then, the variation patterns of safety indicators under 96 groups of wheel wear profiles, corresponding to four different running mileage stages, are further analyzed. Finally the changes of the safety indicators of the vehicle passing through curves under different wheel wear profiles at four different mileage stages with the friction coefficient are studied. The results show that the derailment coefficient, lateral wheelset force, lateral wheel-rail force and lateral car-body acceleration are significantly influenced by the friction coefficient, whereas the wheel load reduction rate and vertical car-body acceleration are not sensitive to changes in the friction coefficient. The depth of wheel wear increases with mileage and friction coefficient, and the wear situation of independently rotating wheels is more severe under the same working conditions. After the vehicle has traveled 40 000 km, the lateral wheel-rail force, lateral wheelset force and derailment coefficient generally exhibit an increasing trend with mileage, while the wheel load reduction rate remains unaffected. Under the combined effects of different friction coefficients and operating mileages, the positions of peak values of the lateral wheel-rail force, lateral wheelset force and derailment coefficient occur at different locations, while the wheel load reduction rate remains relatively stable.
Traffic safety awareness (TSA) of cyclists plays a crucial role in promoting safe behavior, but it is difficult to directly measure due to its multidimensionality and complexity. To investigate the impact of TSA on risky riding behavior (RRB), safety attitude, risk cognition, safety quality, and external environment are selected as the structural elements (or TSA elements) by using the cloud model, and the empirical research is carried out based on questionnaire data. The"TSA-RRB"structural equation model is developed, and the causal pathway from each TSA element to RRB is quantified by Mplus 8.0. The Bootstrap method is applied to verify the mediating roles of safety quality, risk cognition, and safety attitude, and the direct and indirect relationships between the external environment and RRB are sorted; subsequently, a hierarchical regression model is employed to validate the moderating effect of traffic safety knowledge (TSK) between TSA and RRB. The findings of this research are concluded as follows. ① the proposed structural equation model fits well with questionnaire data, and four TSA elements all have significant negative correlations with RRB. Specifically, risk cognition has the most considerable impact on unintentional behavior (-0.331), while safety attitude displays the greatest influence on intentional behavior (-0.332). ② Mediating effects show that the external environment, as an exogenous variable, could either directly act on riding behavior or indirectly affect the behavior through other TSA elements such as safety quality, risk cognition, and safety attitude. ③ The moderation effect of TSK is significant (∆R2 = 0.017, P < 0.05), enhancing the negative correlations between TSA and RRB, and the simple slope relationship between TSA and RRB implies that the effect of TSA on RRB is strengthened when the level of TSK is high.
To address the frequent occurrences of takeaway delivery riders running red-light and the high risk of crashes associated with this behavior, a filed survey is conducted at multiple signalized intersections in Xi'an, the red-light running (RLR) behaviors of delivery riders are investigated. The RLR behavior is taken as the dependent variable, while independent variables included rider personal characteristics, crossing behavior characteristics, and traffic and environmental features. A random parameter Logit model considering heterogeneity in the means and variances was constructed. Parameter estimation was carried out using Halton sequence sampling, and the impact of each independent variable on the dependent variable was quantitatively analyzed through the estimation results and average marginal effects. The findings indicate that Eleme and UU delivery riders have a lower probability of RLR. Variables such as arriving during the second or third phase of the red light, waiting behind the stop line for the green light, and higher conflicting direction traffic volumes significantly reduce the probability of RLR. Conversely, an increase in the number of violators in the same direction, the noon peak hours and evening peak hours significantly increase the probability of RLR. Among these, the variable that most significantly increases the probability of RLR is the evening peak hour, with an average marginal effect of 0.278; the variable that most significantly decreases the probability of RLR is waiting behind the stop line, with an average marginal effect of -0.222. Besides, the parameters of waiting behind the stop line and evening peak hours are random parameter variables, following a normal distribution with means and standard deviations of -1.379, 1.359 and 2.502, 5.360, respectively. Besides, both random parameters exhibit significant heterogeneity in means and variances. For the variable of waiting behind the stop line, arriving during the second phase of the red light increases both the mean and variance of this variable's parameter, hence increasing the probability of RLR and the randomness of its impact on this behavior. For the evening peak hour, a higher volume of motor vehicle traffic reduces both its parameter's mean and variance, thus lowering the probability of RLR and reducing the randomness of its impact on this behavior. Additionally, having only one violator also reduces the variance of the evening peak hour's parameter.
Journal of Transport Information and Safety
(Founded in 1983 bimonthly )
Former Name:Computer and Communications
Supervised by:Ministry of Education of P. R. CHINA
Sponsored by:Wuhan University of Technology
Network of Computer Application Information in Transportation
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Editor-in-Chief:ZHONG Ming
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Publication No.:ISSN 1674-4861
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