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The temperature of axle box bearing is always one of the indicators used to monitor whether the high-speed train is running safely. In this paper, a thermal model of axle box bearing considering the change of bearing lubrication state and the operating condition of the high-speed train was established. Based on the analysis of the generation mechanism of frictional heat inside the bearing, the influence of proportion of grease involved in lubrication was introduced for the first time and a detailed temperature transfer system of the axle box system was established. At the same time, through the axle box bearing-vehicle system dynamics model, the vertical and lateral loads of the axle box bearing under different operating condition were obtained as input parameters of the axle box bearing thermal model, the temperature distribution curve of the bearing under different operating conditions was obtained. Finally, based on the long-term wireless transmission device system (WTDS) temperature monitoring data, the calculation results of the established model were verified. The verification results showed the reliability of the model established in this paper, and showed the necessity of considering the change of the internal lubrication state of the bearing when evaluating the axle box bearing temperature. [ABSTRACT FROM AUTHOR]

The advent of autonomous vehicles has brought about significant advancements in transportation technology, promising safer and more efficient means of travel. However, their full integration into society depends on the accuracy of path-tracking realised by a lateral controller. Lateral control is achieved by regulating the steering angle to minimise the lateral error between the vehicle and a target point at a look-ahead distance on the reference path. This paper investigates the look-ahead distance as it is considered a key parameter that impacts vehicle performance, stability, and energy consumption. A qualitative analysis is performed to deduct a set of rules to adapt the look-ahead distance to three parameters: vehicle velocity, road curvature, and road adherence. Then, an original explicit mathematical formulation is developed for the look-ahead distance as a function of the considered parameters. A fuzzy logic decision for the look-ahead distance is further established and compared with the formulated one. Both approaches are implemented on a look-ahead distance-based lateral controller based on the super-twisting sliding mode control. Simulation results carried out in a joint simulation between Simulink/MatLab and SCANeR $ ^{{\rm TM}} $ TM Studio vehicle dynamics simulator demonstrate the effectiveness of the developed model on vehicle performance, stability, computational efficiency, and energy consumption. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive procedure for the parametric design and analysis of a underwater vehicle rotary docking skirt (RDS) structure. Different types of software were integrated to improve the design efficiency, and different techniques were used to establish an approximate model of the RDS structure with high fitting accuracy. Nondominated sorting genetic algorithm II (NSGA-II) was improved by dynamic adjustment of the population size according to the number of iterations and new crossover and mutation operations (i.e. INSGA-II), which was then applied to a multi-objective optimisation model of the RDS structure. A Pareto solution set was obtained, and a sensitivity analysis was performed on the design variables and objective functions of four representative optimisation schemes. These results can be used to provide a richer selection for designers to reference when designing RDS structures. Abbreviations: RDS; Rotary docking skirt; NSGA-II; Nondominated sorting genetic algorithm II [ABSTRACT FROM AUTHOR]

The electrification of commercial vehicles has led to new wheel torque allocation options for propulsion and braking of articulated heavy vehicles. Each unit or axle can be individually braked or propelled whilst the other units or axles are excluded from such action. This may achieve the best energy efficiency. However, this can also lead to potential yaw stability problems such as jackknifing and trailer swing, especially under bad loading and weather conditions. This paper describes the above instabilities and introduces a nonlinear single-track model to study the vehicle dynamics of the tractor-semitrailer combination. The effects of different vehicle and environment parameters are analysed with this vehicle model. A safe operating envelope for limiting the wheel forces is obtained using this vehicle model. Since the vehicle model introduced in this paper is computationally effective, it can be run online in real vehicles, with an instantaneous safe operating envelope obtained for the momentary conditions. Thus, yaw instabilities such as jackknifing and trailer swing may be avoided. [ABSTRACT FROM AUTHOR]

The vibration of high-speed trains induced by track irregularities is a main factor affecting ride comfort. Especially, the long-wavelength track irregularities can reduce the passengers' ride comfort by increasing the vibration of the high-speed trains. A three-dimensional human body model coupled to a vehicle body and tracks is established to form a coupled human-seat-vehicle-track system for investigating the influence of the long-wavelength track irregularities on ride comfort. The parameters of the seated human model are determined by measurement based on the multi-island GA method. The coupled model is then used to evaluate the ride comfort of high-speed trains using ISO 2631 under the excitation of the track longitudinal level irregularities. The effects of primary, secondary suspension, and seat support vertical stiffness and damping on ride comfort are analysed. The results show that the track's longitudinal irregularities lead to high human body vibration levels and large ride comfort indices (lower ride comfort), especially when the irregularity excitation frequency is near the natural frequency of the high-speed train. The passengers' ride comfort is more sensitive to the vertical secondary suspension stiffness than the other suspension parameters. [ABSTRACT FROM AUTHOR]

This paper presents a novel probabilistic data-driven approach to trip-level energy consumption estimation of battery electric vehicles (BEVs). As there are very few electric vehicle (EV) charging stations, EV trip energy consumption estimation can make EV routing and charging planning easier for drivers. In this research article, we propose a new driver behavior-centric EV energy consumption estimation model using probabilistic neural networks with model uncertainty. By incorporating model uncertainty into neural networks, we have created an ensemble of neural networks using Monte Carlo approximation. Our method comprehensively considers various vehicle dynamics, driver behavior, and environmental factors to estimate EV energy consumption for a given trip. We propose relative positive acceleration (RPA), average acceleration, and average deceleration as driver behavior factors in EV energy consumption estimation, and this paper shows that the use of these driver behavior features improves the accuracy of the EV energy consumption model significantly. Instead of predicting a single-point estimate for EV trip energy consumption, this proposed method predicts a probability distribution for the EV trip energy consumption. The experimental results of our approach show that our proposed probabilistic neural network with weight uncertainty achieves a mean absolute percentage error of 9.3% and outperforms other existing EV energy consumption models in terms of accuracy. [ABSTRACT FROM AUTHOR]

This paper proposes an optimal lane-changing and control strategy to solve the collision avoidance of intelligent vehicles in highway driving. A quintic polynomial lane-changing trajectory model is established in the Frenet frame, and the trajectory planning problem is transformed into the optimisation problem of lane-changing target coordinates. To consider the multiple environmental factors on vehicle lane-changing, the feasible region of the lane-changing target point was generated based on the lateral acceleration limitation and the safe distance constraints. The performance evaluation indexes were established, considering efficiency, comfort, lateral slip, and lane offset. The multi-objective optimisation problem is solved in the feasible region, and the optimisation results were applied to the collision detection process. In addition, considering the nonlinear characteristics of tire force caused by sudden lateral movements of vehicles at high-speed, a vehicle dynamics model based on the Magic Formula is established, and Model Predictive Control is applied to track the expected trajectory. Simulation results show that this strategy can plan suitable lane-changing trajectories in high-speed working conditions and achieve vehicle collision avoidance. [ABSTRACT FROM AUTHOR]

Research and development of innovative suspension components for rail vehicles have involved huge investments in recent years. Research efforts have focussed on designing and optimising suspension systems to deal with the new challenges introduced in railway dynamics by the continuous increase in vehicle speed. In particular, yaw dampers have been a relevant research topic due to their influence on vehicle stability. In this context, this paper aims to propose a Hardware-In-the-Loop (HIL) methodology for testing yaw dampers under experimental conditions close to real operating scenarios, comparing the influence of different prototypes on the stability of high-speed rail vehicles. A reduced vehicle model is proposed for real-time integration in HIL tests. This model provides a reference stroke to be imposed on the prototype tested, considering the actual damping force provided by the device being analysed. Two yaw damper prototypes are introduced to validate the proposed methodology by means of comparative analysis at different vehicle speeds. The experimental results provided by the HIL test bench are then compared with corresponding analysis done using Multi-Body (MB) simulations. The proposed HIL methodology has proved to be able to test physical prototypes and define guidelines to assist damper manufacturers developing and optimising yaw damper components. [ABSTRACT FROM AUTHOR]

Four-wheel steering (4WS) is an effective technique to improve handling performance and lateral stability of road vehicles. Conventionally, controllers utilise the driver's actions and vehicle dynamics to coordinate front and rear-axle steering. This paper proposes a novel approach for 4WS controller design, based on the concept of Artificial Flow Guidance (AFG), which relies on a spatially distributed motion reference through a two-dimensional vector field. This field provides high-level guidance while lower-level steering controllers to control axle centres motions relative to the flow. These flow vectors, computed in real-time via simple geometric construction, can be pre-computed globally to evaluate the guidance algorithm's efficacy. When controlling only the front axle, this same approach can function as an autonomous driving system. Relying solely on a spatial reference field and control targets' velocities enables the controller to work in a simple and robust fashion, without using a reference vehicle dynamics model or lengthy parameter tuning. The proposed approach's effectiveness is validated through co-simulation with MATLAB/Simulink and the CarMaker simulation platform. AFG control performance is found to be at least comparable to that of more complex 4WS controllers using methods such as MPC; in the cases considered, AFG provides superior path-tracking performance. [ABSTRACT FROM AUTHOR]

The paper presents a novel control strategy for autonomous vehicles, which can effectively handle the nonlinear effects and uncertainties of the controlled system. This solution is based on a new formulation of the ultra-local model-based control approach. This method can deal with the unknown dynamics and other uncertainties of the vehicle without any further measurement or complex modelling process. The control methods require a reduced-complexity nominal linear model of the system, and the unknown part is continuously estimated by the proposed ultra-local model. The proposed control-oriented vehicle modelling method leads to an increased performance level of vehicle motion. The effectiveness of the proposed method through a high-fidelity vehicle simulator (CarMaker) is illustrated. Moreover, the operation of the control through its implementation on a test vehicle of ThyssenKrupp is also demonstrated. [ABSTRACT FROM AUTHOR]

Semi-active primary suspensions are an effective means of improving ride quality in high-speed railway vehicles in relation to the mitigation of car-body bending vibration. In this paper, prototype magnetorheological (MR) dampers are tested and the results are used to define a mathematical model of the dampers. Then, three control schemes for semi-active primary suspensions are proposed: Skyhook, LQG and Mix-1-Sensor, and their performance is assessed by means of Hardware-In-the-Loop (HIL) tests considering a simple quarter-vehicle model which is run on a real-time board and set in interaction with one physical MR damper. The results show that all three considered control strategies lead to a reduction of car-body vibration by around 30% and a very good agreement is found between HIL tests and numerical simulations in which the physical damper is replaced by the mathematical damper model. The damper model is finally interfaced with a flexible multi-body model of the complete vehicle to provide further assessment of semi-active control. The results of the latter simulations show that the semi-active suspension could provide an improvement of the $ {N_{mvz}} $ N mvz ride quality index in the order of 40–45% with respect to the passive vehicle for all three control schemes. [ABSTRACT FROM AUTHOR]

Polygonalization is a typical non-uniform wear phenomenon that affects the performance and comfort of the vehicle/track system. Therefore, the vehicle system performance could be strictly troubled by polygonal damage close to the wheel circumference at the wheel/rail contact. A 3D vehicle/track an EMU type train consisting of 8 coupled vehicles model has been established. The coupled model car body and bogie frame are considered rigid and integrated with the flexible wheelset, rail, and slab track to investigate the elastic deformation caused by the impact load induced by the wheel polygonalization. The flexible track can be incorporated into the multi-body vehicle model using the movable reference frame formulation. Uncertainty parameters are presented, such as passenger weight, wind force, coefficient friction, and suspension variation. The proposed research is validated based on the existing research work and shows excellent agreement. The simulation result deliberated the vertical wheel-rail force, wheelset acceleration, rail acceleration, rail displacement, and slab track acceleration. The results of this study show that as the wheel polygonal damage amplitude increase, the value of wheel/rail normal forces and the dynamic vibrational response of the wheelset axle increase. Additionally, polygonal wear-induced impact stresses may cause the wheelset axle to resonate. When wheel polygonal damage amplitude and uncertainty parameters are corporate into the system dynamics, the maximum magnitude of the wheelset, rail, and slab track acceleration increases. Besides, the train failure degree is comparable to the polygonised wheel harmonic order, defect parameters, and amplitude of out-of-roundness. [ABSTRACT FROM AUTHOR]

To increase vehicle dynamics modelling accuracy in simulation environments, in this work, we propose a model, where the mutual influence of the vehicle dynamics and tyre wear is taken into account. In this context, simulation-oriented models aim at representing the main features of the vehicle dynamics, while keeping the complexity low, making them suitable for control-oriented analyses and design. The wear model quantifies tyre wear as a tyre mass loss depending on the tyre-road interaction, derived from the vehicle dynamics and kinematics; then, the outcome of this model is consequently used to update the tyre friction characteristics, by modifying the main parameters of the Pacejka's magic formula. We also discuss the steps required to use the model in two-wheeled vehicles, where the roll dynamics plays an important role in the tyre wear. The main features of the developed model are discussed on a motorcycle, as a simulation case-study. [ABSTRACT FROM AUTHOR]

In a typical traffic scenario, automated vehicles are required to interact with surrounding traffic participants, e.g. human-driven vehicles, pedestrians, etc. In this paper, a novel adaptive authority allocation strategy considering the social behaviours of surrounding vehicles is proposed for the shared steering control (SSC) of automated vehicles. First, a Koopman-based potential-field-driven distributed model predictive control (K-PF-DMPC) method is proposed for the modelling of vehicle interaction to describe surrounding vehicle's social behaviour. This method effectively deals with the nonlinearity embedded in the non-cooperative game-based vehicle interaction model, so that the analytical form of Nash equilibrium can be derived for a fast online solution. Then, the SSC system of the automated vehicle is implemented by a weighted summation method. To balance the driving performance and intervention degree while considering the surrounding vehicles' social behaviours, a hybrid fuzzy strategy (HFS) is proposed for allocating the control authority between the driver and automation. The value of authority allocation coefficient is calculated by fusing the outputs from two shared fuzzy controllers, i.e. the enhanced and weakened shared fuzzy controllers, in accordance to the belief of the surrounding vehicle's type. Several numerical simulations and driver-in-the-loop simulator experiments are conducted for validation. Results show that the proposed strategy can provide appropriate steering intervention to the driver owing to the consideration of the surrounding vehicle's social behaviour and obtains the best driver-automation collaboration performance compared with the comparative groups. [ABSTRACT FROM AUTHOR]

We present a general approach to model the motion of a rigid body ground vehicle on a smooth nonplanar road surface. We generalise planar control-oriented models while preserving standard model states, inputs and outputs. We derive our approach from first principles, apply it to existing vehicle modelling approaches and test it through real-world experiments. We demonstrate that our approach improves upon the prediction accuracy of planar models. [ABSTRACT FROM AUTHOR]

In this paper, a typical motion-based modelling and tracking issue is investigated for vehicle targets in linear road segment by a variable structure multiple model (VSMM) method. Vehicle target motions in a road with multiple lanes are described by typical lane keeping and lane changing manoeuvres. To describe trajectories of typical manoeuvres, an Ornstein–Uhlenbeck process and a sine half-cycle are used to model lane keeping and lane changing motions in lateral direction, respectively. Note that starting point and length of lane changing motion are unknown in target tracking. Time-varying model sets are designed based on the current motion model with different motion parameters. A VSMM tracking frame is constructed to obtain target state estimates with time-varying model set. The effectiveness of the proposed typical motion-based tracking scheme is displayed by simulation results on road vehicle tracking. [ABSTRACT FROM AUTHOR]

A comprehensive RFD-FTC-DCA system is proposed for the hypersonic vehicle with saturation constraints to resist the control surface damage, actuator faults, disturbances and parameter perturbation. Firstly, the hypersonic vehicle fault model is established. Secondly, the robust fault detection (RFD) observer is designed to detect the control surface damage and actuator faults accurately under the influences of disturbances and parameter perturbation. Thirdly, the fault-tolerant control (FTC) law is designed to resist the control surface damage, actuator faults, disturbances and parameter perturbation simultaneously. Finally, a dynamic control allocation (DCA) algorithm is designed to reallocate the FTC law and limit the deflection angle and velocity within saturation constraint. The comparison simulation results are presented to demonstrate that the RFD observer can detect the faults accurately and reduce false alarm rates effectively, the FTC law can resist the control surface damage, actuator faults, disturbances and parameter perturbation simultaneously, and the tracing errors of attack angle, side-slip angle and roll angle are only $ \pm 0.7^\circ $ ± 0.7 ∘ , $ \pm 0.2^\circ $ ± 0.2 ∘ and $ \pm 1.5^\circ $ ± 1.5 ∘ , respectively, and the DCA algorithm can reallocate the FTC law and limit the deflection angle and velocity within saturation values. [ABSTRACT FROM AUTHOR]

Vehicle and occupant responses in 35 mph NCAP tests were determined for small-midsize passenger cars grouped around model year (MY) 1980, 1990, 2000, 2010 and 2020. A baseline was established with 1980 vehicles not designed for NCAP. The results of four decades of vehicles designed for NCAP were compared to the baseline. The study also determined the risk for serious injury (MAIS 3 + F) by vehicle model year (MY) using 1989–2015 NASS and 2017–2020 CISS. It explored safety trends in frontal crashes over 50 MYs of vehicles. The 1980 baseline group was established with 10 1979–1983 MY passenger cars weighing <1,500 kg. Four decades of vehicle crash tests from five manufacturers established trends in vehicle dynamics and dummy responses over four decades of vehicles designed for NCAP. Triaxial acceleration of the head and chest were reanalyzed for each test to have a consistent set of responses over five decades. The risk for serious injury (MAIS 3 + F) to the driver and front passenger was determined by vehicle MY using 1989–2015 NASS and 2017–2020 CISS with belted and unbelted drivers and right-front passengers. The data was sorted in four MY groups 1961–1989 MY, 1990–1999 MY, 2000–2009 MY and 2010 MY-2021 MY. The risk for MAIS 3 + F injury was determined with standard errors using weighted data. The 1980 NCAP tests brought about changes in vehicle structures and occupant restraints by 1990; however, HIC15 and 3 ms chest acceleration have not changed much the past 20 years since the use of advanced airbags and seatbelts with pretensioner and load-limiters. For the driver, HIC15 dropped 40 ± 19% from the 1980 to 1990 NCAP tests and dropped further to 76 ± 32% in 2020. The percentage drops after 1990 were not statistically significant. The driver 3 ms chest acceleration dropped 18 ± 5% from 1980 to 1990 and plateaued with 22 ± 6% in 2020. For the front passenger, HIC15 dropped 68 ± 52% from the 1980 to 1990 NCAP tests and plateaued at 71 ± 49% in 2020. The passenger 3 ms chest acceleration dropped 13 ± 5% from 1980 to 1990 and has fluctuated with minimal change. Injury risks based on responses show the same initial drop in 1990 and have remained essentially constant. Nothing meaningful has changed in dummy responses in the past 20 years of NCAP testing. The field data found the belted driver MAIS 3 + F risk was 1.66 ± 0.37% in 1961–1989 MY vehicles and 1.39 ± 0.33% in 2010–2021 MY vehicles. For belted right-front passengers, the risk was 1.52 ± 0.39% in 1961–1989 MY vehicles and 1.42 ± 0.46% in 2010–2021 MY vehicles. The field data shows no meaningful change in injury risk in 50 MYs of vehicles. NCAP involves 35–40 mph delta-V, which represents a small fraction, 0.33%, of belted occupant exposure and only 8.6% of severe injury based on 1994–2015 NASS. The NCAP test lacks field relevance. Manufacturers are merely "tuning" the restraint systems for star ratings without meaningful changes in field injury risks the past 20 years. There are disbenefits of "tuning" safety for a single, high-severity crash when most of the severe injury occurs in lower severity crashes. NHTSA should reevaluate plans to change the dummy to Thor and add BrIC injury criteria to assess NCAP responses. These changes would cause manufacturers to further "tune" structures, restraints and interiors without meaningful effects in real-world crashes. [ABSTRACT FROM AUTHOR]

Although Van Dijk and Kintsch's model of text comprehension has been shown to be an effective theory for describing many findings with academic implications, their model has far reaching potential beyond the classroom – perhaps into the courtroom. At the end of a criminal trial, jurors are provided with a set of instructions regarding how they should apply relevant law to the present case. Unfortunately, most current juror instructions are very difficult to comprehend. Though linguistically based simplifications of these instructions have improved comprehension for jury-eligible adults, comprehension remains quite poor resulting in jurors basing decisions on stereotypes and biases rather than the law. The present essay reviews some of the research that has been conducted on improving juror comprehension, the effectiveness of some of these attempts, and makes an argument for utilizing Van Dijk and Kintsch's situation model as a vehicle for additional improvement in juror instructions and hence juror comprehension. [ABSTRACT FROM AUTHOR]

Countdown timers impact driver behavior significantly and are widely used at signalized intersections in many countries. Literature shows potential vehicle class-specific temporal and spatial variations in driver behavior in the presence of timer. Therefore, first, this paper analyzed the temporal, spatial, and vehicle class-specific impacts of timer on driver behavior in heterogeneous traffic conditions based on variations in acceleration. Second, a Long Short-Term Memory model was developed to model vehicle discharge, incorporating the heterogeneity of traffic and impacts of timer. The performance of the model was compared with that of the Intelligent Driver Model using field trajectory data from three signalized intersections in Kerala, India. The model accurately predicts the following behavior with mixed spacing errors of 0.24 to 0.35 and an average mean squared error of spacing of 1.23. The results were better than, or comparable to, results from recent data-driven car-following models and significantly better than IDM. [ABSTRACT FROM AUTHOR]

The so-called g-g diagram is widely employed to assess the performance of road vehicles since it provides the maximum longitudinal and lateral accelerations that can be extracted from the selected vehicle. The different points of the g-g diagram are usually computed independently from one another, e.g. the maximum longitudinal accelerations corresponding to given lateral accelerations are computed sequentially. In this work, the problem of computing the points of the g-g diagram is transformed into an optimal control problem, which allows to avoid one of the most annoying practical problems often encountered when deriving such diagrams, namely the 'jumps' between different solutions (i.e. large slip vs. small slip solutions at similar lateral acceleration) in adjacent points along the g-g envelope. In the proposed method, the objective is to maximise the area enclosed within the g-g diagram, which has a polar representation. The rate of change of the radial coordinate is the control input. Additional constraints are included to enforce the continuity between the states of the vehicle model in adjacent points along the envelope. These conditions can hardly be enforced using standard methods based on sequential and independent computation of the g-g points. An example of the application of the method is demonstrated on the classic double-track car model with nonlinear tyres. [ABSTRACT FROM AUTHOR]

In this paper, we compared the linear and nonlinear motion prediction models of a long combination vehicle (LCV). We designed a nonlinear model predictive control (NMPC) for trajectory-following and off-tracking minimisation of the LCV. The used prediction model allowed coupled longitudinal and lateral dynamics together with the possibility of a combined steering, propulsion and braking control of those vehicles in long prediction horizons and in all ranges of forward velocity. For LCVs where the vehicle model is highly nonlinear, we showed that the control actions calculated by a linear time-varying model predictive control (LTV-MPC) are relatively close to those obtained by the NMPC if the guess linearisation trajectory is sufficiently close to the nonlinear solution, in contrast to linearising for specific operating conditions that limit the generality of the designed function. We discussed how those guess trajectories can be obtained allowing off-line fixed time-varying model linearisation that is beneficial for real-time implementation of MPC in LCVs with long prediction horizons. The long prediction horizons are necessary for motion planning and trajectory-following of LCVs to maintain stability and tracking quality, e.g. by optimally reducing the speed prior to reaching a curve, and by generating control actions within the actuators limits. [ABSTRACT FROM AUTHOR]

The safety of increasingly automated vehicles is of great concern to regulators, yet crash rates are generally reported by manufacturers using proprietary metrics with limited source data. Without consistent definitions of crashes and exposure, automated vehicle crash rates cannot be meaningfully compared with baseline datasets. The objective of this study was to establish methods to normalize automated vehicle crash rates using one manufacturer's crash reports as a case study. The manufacturer's quarterly crash rates for vehicles using SAE Level 1 and Level 2 automation were compared. Road type was controlled for using data from a naturalistic driving study with the same model vehicles, while driver age was controlled for using demographic ownership surveys. Although Level 2 vehicles were claimed to have a 43% lower crash rate than Level 1 vehicles, their improvement was only 10% after controlling for different rates of freeway driving. Direct comparison with general public driving was impossible due to unclear crash severity thresholds in the manufacturer's reports, but analysis showed that controlling for driver age would increase reported crash rates by 11%. These results establish the need for detailed crash data, crash definitions, and exposure and demographic data in order to accurately assess automated vehicle safety. [ABSTRACT FROM AUTHOR]

Faults of railway suspension units may endanger vehicle operation safety. Therefore, timely fault detection of railway suspension is necessary. The reported fault detection method that uses Bidirectional Long Short-Term Memory (BiLSTM) neural network in a denoising autoencoder fashion suffers from a shortcoming that the condition monitoring data under faulty states needs to be ultilized to determine the added noise level. Such data is not always available in practice. In this paper, we modified the BiLSTM such that the output data point is excluded from the input when predicting this specific output data point. The requirement of using condition monitoring data under faulty states is therefore relaxed, as the modified BiLSTM is free from determining the level of added noise. A case study on railway suspension fault detection was presented. We used the railway vehicle dynamics model to generate car body vibration under healthy, three levels of reduced first suspension stiffness states, and three levels of reduced first suspension damping states. We compared the performance of the modified BiLSTM with the linear autoregression model, LSTM, and BiLSTM-DAE models. The results have shown that the modified BiLSTM-based fault detection method performs the best, having the highest area under the receiver operating curve. [ABSTRACT FROM AUTHOR]

This work describes the development of a vehicle state estimator, designed to be employed onboard in real-time, based on the data acquisitions already available within the vehicle CAN bus infrastructure. The proposed estimation algorithm, taking into account the suspension elasto-kinematics, the longitudinal, lateral and combined dynamics of the tyres as well as the aligning interaction torques at the ground, represents at the current stage a significantly complete tool, since it also provides an estimation of road slope and banking angles, generalising the adoption of the presented vehicle model even on highly inclined roads. A further advantage of the presented estimator consists of its capability to identify in real-time and with a good level of accuracy the tyre/road interaction physical characteristics in terms of grip and cornering stiffness. [ABSTRACT FROM AUTHOR]

Mobility is a vast and comprehensive system where many new multimodal technology revolutions occur. To make strategies of sustainable development, policy makers particularly focus on the residents’ trip scenarios in the long-term future affected by policies but not the extreme accuracy of the predictions. In this paper, we construct a strategic and integrated model of residents’ travel demand and trip pattern based on system dynamics methods. Changes from and relationships between policies, markets and consumers under electrification, automation and sharing revolution in mobility have been considered in this model. This model follows the utility methods in travel cost calculation from MARS and retains the original framework of travel pattern. Moreover, it includes new modes and models under technology revolutions such as (1) new sharing patterns: paratransit; (2) new travel modes: customized shuttle bus and sharing cars and (3) new vehicle models: EVs and Avs. As using the three-level classification system of ownership—mode—model, this strategic analysis model demonstrated a comprehensive structure of future mobility. The validity of model was verified through a case study of Shanghai 2035 with three scenarios developed under possible policy directions. [ABSTRACT FROM AUTHOR]

xComputational representation of real-world systems plays an important role in vehicle analysis. Aiming to improve mobility systems, this article presents the development of a chassis dynamometer and vehicle model describing the vehicle longitudinal dynamics considering the tire-bench contact. The model simulates the longitudinal vehicle-bench tests where the system is powered by the bench's electric motor and the gearbox in the neutral position, considering tire interaction forces, rolling resistance, and system losses. It was implemented in Matlab/Simulink™ and validated by coast-down experiments, starting at 60 km/h and 100 km/h, where the model result curves presented an appropriated representativity for the experimental data. A total movement resistance analysis resulted in a mean error of 6.71% when compared to experimental data, while the literature slip-independent equations presented mean errors between 31.94% and 77.61%. The developed model is a representative approximation of the vehicle-dynamometer set and can predict longitudinal experiments, helping the vehicle evaluation process, and saving time and resources. [ABSTRACT FROM AUTHOR]

To enhance the lateral stability of a certain type of high-speed train under bogie's active control, characteristics of inertial actuators that generate control force in the active control system are studied, the control delay of the whole Hardware-in-the-Loop (HIL) system is measured, and multi-objective optimisation for feedback parameters with or without the control delay is achieved in this study. A linear model of bogie lateral dynamics, with two inertial actuators, acting on the front and rear end beams, is established for the optimisation. Correspondingly, a nonlinear vehicle model is established in the Simpack platform for both mathematical simulation and HIL simulation to verify the control effects. As the force source of active control, dynamic characteristics of the inertial actuator with different control strategies are examined. Multi-objective optimal control is carried out on the linear active bogie models with and without the delay measured in the experiment to improve the bogie hunting stability. The control method is then evaluated in a nonlinear vehicle model and HIL simulation. Simulation results show that the lateral dynamic performance of the high-speed train can be effectively improved with the active stability system even with a large time delay. [ABSTRACT FROM AUTHOR]

Semi-active suspensions are seen as a promising technology to improve ride quality in high-speed railway vehicles as they provide substantial benefits not achievable through an optimisation of the passive suspension while avoiding some drawbacks of full-active control. Previous works showed that semi-active primary suspensions (SAPS) offer significant improvement of ride quality. However, published implementations of this concept did not consider the coupling effects between car-body and bogie vibrations, which play a decisive role in the success of control strategies for SAPS. This paper provides a comprehensive analysis of SAPS to improve vehicle ride comfort, with special attention to the mitigation of car-body bending vibration. A vehicle model considering the coupling of car-body bending and bogie pitch is proposed and used for the synthesis of an LQG controller. The performance of the semi-active suspension and controller is assessed using a detailed flexible multibody system of a high-speed vehicle. The proposed control scheme is shown to be highly effective in reducing car-body vibration in the entire frequency range of interest from 1 Hz to20Hz. A remarkable ride comfort improvement is found in the entire speed range from 150 km/h to 350 km/h. [ABSTRACT FROM AUTHOR]

A growing number of studies have demonstrated the effectiveness and superiority of reverse engineering in using axle box vibration acceleration signals to deduce the operation state of wheelsets. However, there is a lack of discussion and summary on the overall mapping relationship between wheel excitation and axle box response, and there has been no detailed investigation on resonance characteristics of axle box. To address the deficiency, a novel resonant excitation loading method is proposed, which is applied to the vehicle model with flexible wheelset and axle box. Amplitude frequency response (AFR) curve of the resonance characteristics of axle box is obtained. AFR is used to characterise the characteristics of various excitation states of wheel, including wheel polygon, wheel tread flat, and wheel-rail separation state, and the corresponding evolution law is revealed. Finally, through two case studies, the guiding role of axle box resonance characteristics on wheel operation status detection is discussed in detail. Analyses show that mastering the resonance characteristics of axle box is an effective way to deduce the operation status of wheel based on the complex axle box vibration response signal, and it will provide a basis for the quantitative evaluation of wheel local damage. [ABSTRACT FROM AUTHOR]

Vehicle active safety system is the hotspot of current research and development, and the road adhesion coefficient is one of the essential parameters in the development of automobile active safety system, which plays a pivotal role in automobile safety. To improve the real-time performance and accuracy of the road adhesion coefficient, this paper proposes different control methods and compares and analyzes them. To accurately estimate the road adhesion coefficient in real-time, an eight-degree-of-freedom vehicle model was adopted in this paper. According to the tire torque and wheel speed, the adhesion coefficient was estimated based on the second-order nonlinear extended state observer. The experimental data, such as slip rate, using the improved tire model, is based on the recursive least squares method with forgetting factor and fuzzy logic algorithm real-time of tire-road friction coefficient estimation. The results show that the observer can effectively observe utilisation adhesion coefficient, and both control algorithms can estimate the road adhesion coefficient in real-time, effectively and quickly. On different roads, the use of the recursive least squares algorithm resulted in higher estimation accuracy, better robustness, and better control effect than using a fuzzy logic algorithm. [ABSTRACT FROM AUTHOR]

In this study, the resistance characteristics of the amphibious vehicle in the transitional stage are studied. A deformable track wheel is designed and its effect on the amphibious vehicle's resistance is studied. The numerical calculation method based on the RANS solver and the towing test method is used to analyse the hydrodynamic performance of the amphibious vehicle. Based on the comparison of the vehicle model with no wheel, the influence of wheels on additional resistance at the groove fault is studied. The inclination angles of the front and rear deformation wheels are studied respectively. The influence and principle of the track wheel configuration on drag are analysed and expounded in terms of pressure distribution, water climbing and spray on the wheel grooves, and the hull attitude. Finally, an adjustment strategy of the deformable configuration wheel in the transition stage is proposed. [ABSTRACT FROM AUTHOR]

This paper explores the optimization for the integrated vehicle routing of package collection and delivery in rural areas, based on the coverage idea and customer self-pickup strategy. The purpose is to optimize package collection and delivery in rural areas with the scattered and small-scale demand for the express service. An integrated vehicle routing model for rural package collection and delivery is established with regard to the radius of customer self-pickup, via taking the sum of operation cost, transportation cost, time penalty cost and carbon emission cost as the optimization goal. A two-stage algorithm based on the improved k-means clustering algorithm and genetic algorithm is designed to solve the model. Ziyuan county of Guangxi province is taken for typical example. The simulation results show that the optimization model can raise vehicle loading rate and service coverage rate, while reducing cost. A rise in the customer's self-pickup radius and the number of packages collected and delivered can decrease the unit collection and delivery cost, and it is found that carbon emissions have little effects on the optimization of vehicle routing from the perspective of cost. [ABSTRACT FROM AUTHOR]

This paper proposes a novel prioritisation model predictive control for improving the handling and stability of all-wheel-drive vehicles configured with an electric motor and an open differential per axle with differential braking capability. The configuration of the powertrain provides a significant handling improvement by optimising front/rear torque distribution. The controller gives a high priority to front/rear torque distribution and, if needed, activates the differential braking. A coupled force prediction model of the vehicle handling dynamics is developed to capture the interaction of longitudinal and lateral tyre forces. Since differential braking causes speed drop, energy waste, and noise, two control actuations are prioritised: (1) front/rear torque shifting, (2) differential braking. Appropriate stability constraints are defined for the vehicle yaw rate and sideslip, dividing the sideslip-yaw rate phase plane into three regions – stable, marginal, unstable – based on which three control objectives are defined. Then, the priorities of the control actuations and the control objectives are combined, and a model predictive control structure is developed for this multi-objective multi-actuation control problem. The predictive controller prioritises the objectives and actuations through the prediction horizon. The performance of the proposed controller is thoroughly evaluated through numerical and full vehicle experimental studies. [ABSTRACT FROM AUTHOR]

As racing vehicles become more complex, optimising the interaction between subsystems becomes critical for racing performance. In this work, we incorporate two such subsystems into a vehicle model. We investigate the performance benefits of a four-wheel-drive vehicle with independent control over its in-hub motors and active control on the rear wing flap rotation. The performance is evaluated by solving minimum lap time optimal control problems (OCP) for various vehicle configurations. The OCP is transformed into a nonlinear programming problem through direct collocation and is solved by an interior point method. The four-wheel-drive configuration performs better than rear-wheel drive in terms of lap time, finishing the Barcelona circuit 4 % faster. The benefits come mainly from higher longitudinal accelerations. Active aerodynamic control improves performance regardless of the propulsion configuration, leading to another 1 % of lap time improvement on the Barcelona circuit. The optimal aerodynamic control strategy is different between propulsion configurations, particularly on corner exits. This model enables the exploration of optimal torque vectoring controls and their interaction with a vehicle's active aerodynamics. This is needed to guide the design of the increasingly complex racing vehicle controllers of the future. [ABSTRACT FROM AUTHOR]

Step increase of electric motor torque results in wheel slip during the acceleration of battery electric vehicle (BEV), making vehicle body instability paramount. This is particularly challenging for regulating the torque of electric motor to keep stability in the process of acceleration, for which regulating the wheel slip to an ideal set-point is difficult for the central driving powertrain that adopts one electric motor to drive both left and right wheels by a differential. While much of the research on acceleration slip regulation has focused on solving the wheel anti-slip of internal combustion powertrain by electronic stability programme, comparatively little is known about the wheel slip control by electric motor torque of the central driving powertrain that is the most common style of driveline in the market of BEV currently. Here we discuss a series of studies on the acceleration slip regulation by electric motor torque that, collectively, design an approach of how the nonlinear model predictive controller based on a novel driving dynamics model regulates the wheel slip to an ideal set-point from the ideal slip ratio curve. Testing and validating this approach embedded into vehicle control unit are carried out in a BEV to fully realise the wheel slip control by electric motor torque during the acceleration. [ABSTRACT FROM AUTHOR]

In order to perform optimizations with vehicle models efficiently, the resource requirements for a simulation must be reduced. In this article, approaches for the physical reduction of the vehicle model are presented, which automatically removes components or elements from the model. For the reduction, evaluation functions considering the crash behaviour of the model are used, as well as geometric methods that ensure its viability. Suitable boundary conditions, such as an equivalent mass or displacements of individual nodes, are applied to the reduced model to recover the kinematics. Finally, the practical application of the methodology is presented by two optimizations. [ABSTRACT FROM AUTHOR]

The introduction of more automation into our vehicles is increasing our ability to avoid or mitigate the effects of collisions. Early systems could brake when a likely collision was detected, while more advanced systems will be able to steer to avoid or reconfigure a collision during the same circumstances. This paper addresses how the post-impact motion of an impacted vehicle could be included in the decision-making process of severity minimisation motion planning. A framework is proposed that builds on previous work by the authors, combining models from motion planning, vehicle dynamics, and accident reconstruction. This framework can be configured for different contexts by adjusting its cost function according to relevant risks. Simulations of the unified system are carried out and analysed from the perspective of vehicle model complexity and collision parameters sensitivity. Additionally, effects are highlighted concerning different modelling decisions, with respect to vehicle dynamics models and collision models, that are important to consider in further research. [ABSTRACT FROM AUTHOR]

Efficient path tracking plays a key role in the overall ride experience of Autonomous Vehicles (AVs). Model Predictive Control (MPC) is one of the most competent techniques which is capable of handling multiple variables and constraints. The performance of this controller heavily relies on the proper choice of the vehicle model used to predict future states. This work proposes a novel MPC framework for the effective adoption of vehicle models to achieve a compromise between MPC's performance and computational cost. To this aim, a Switched MPC (SMPC) using vehicle models with different levels of complexity and fidelity is developed. The SMPC uses a novel supervision scheme to adopt the appropriate vehicle model based on the models' prediction error and MPC's solution time. Two different configurations of SMPC are implemented: (1) A Fuzzy Logic System (FLS), and (2) An adaptive switching supervisor. The outcomes show that both approaches can perform path tracking accurately on roads with varying curvatures for different AV speeds. Moreover, comparisons with the conventional MPCs show that the proposed controllers can perform comparably with selective use of a complex vehicle model. Notably, they benefit from a higher computation efficiency from sidestepping the most complex models during path tracking. [ABSTRACT FROM AUTHOR]

Active steering technology can effectively solve the contradiction between the running stability and curving performance of traditional bogies. However, the execution deviations between the actual and theoretical steering actions, which expressed in this paper as equivalent curvature differences, would occur when mileage error or other abnormal operating conditions happens. In this study, the influence of equivalent curvature differences on running safety was studied, and a steering efficiency evaluation method was proposed. First, the equivalence between the wheel–rail relationship in the under- and over-steering states and that in the passive state was demonstrated by combining analytical and numerical simulation methods. It was concluded that under- and over-steering states do not worsen the running safety of rail vehicles. Then, the formula for wear number with the equivalent curvature difference as the independent variable was derived based on the linear model of the rail vehicle, and the accuracy of the formula was verified using the nonlinear model. Finally, a steering efficiency evaluation method was established, and a steering efficiency evaluation under different equivalent curvature differences and steering rates was conducted. The results of this study can provide a reference for engineering active steering systems. [ABSTRACT FROM AUTHOR]

As the greenhouse gas emission regulations have strengthened, establishing a sustainable transportation system has become more essential. Thus, studies on the transportation system using electric vehicles have received more research attention. However, operation using electric vehicles has obstacles such as technical limitations of vehicle batteries and insufficient number of charging stations, which can be much affected by the traffic flow changes. Therefore, we propose a robust electric vehicle routing model under road traffic flow uncertainty. An arc segmentation method is used to apply the road traffic flow uncertainty more realistically and mitigate the conservativeness of the solutions. We also use the genetic algorithm with three-layer chromosome encoding schemes. Three-layer chromosome encoding schemes guarantee the feasibility of the solutions by checking the product and battery capacity of electric vehicles. The experiments show that the solutions of the robust electric vehicle routing model tend to visit charging stations more often due to the uncertain road traffic flow. However, simulation experiments show that the robust electric vehicle routing model provides better performance. [ABSTRACT FROM AUTHOR]

This paper deals with the control of a hydraulically interconnected suspension system to improve the handling performance of the vehicle. A seven-degrees-of-freedom MATLAB/Simulink vehicle model and an Adams/Car model are used for simulation purposes. A Simscape model for analysing the hydraulic subsystem is also employed. It was observed that the yaw rate and roll responses of the vehicle are influenced to a large extent by the flow control valve opening values. The handling performance of the vehicle was investigated by the control of the orifice valves and their adjustment according to the lateral acceleration inputs. Considerable improvements were obtained in the handling qualities without sacrificing the ride responses, compared to the responses of a passive interconnected suspension. [ABSTRACT FROM AUTHOR]

Vehicle safety performance is important to reduce occupant injuries during accidents. In general, vehicle manufacturers are utilizing analytical models to predict the vehicle passive safety performance during the early design stage. The two popular methods are the Occupant Limit Criterion (OLC) and Vehicle Pulse Index (VPI). In this paper, new VPI parameters are proposed to predict the driver 3 ms chest acceleration of Hybrid III 50th percentile (H350) in B-segment vehicle subjected to generic crash load cases. A good correlation between the newly optimized VPI parameters with the measured 3 ms chest acceleration is observed in this work. More refinement can be further included to improve the robustness of the new proposed parameters by adding more sampling data. [ABSTRACT FROM AUTHOR]

Objective: Vehicle collisions are described with the help of collision severity parameters such as energy equivalent speed (EES) and the collision-based change of velocity (delta-v). These serve as an input for injury outcome estimations through injury risk functions (IRF) or for the virtual assessment of active safety systems in case of a modified collision. A novel method was developed with the aim of simulating various vehicle collisions within a short time frame while ensuring the accuracy of the collision severity parameters. Methods: Previously developed three-dimensional EES models were used in this study. They were used to compute 2 D vehicle substitute models, which are deformed during a new, time-discrete method. By using fundamentals of mechanical impact calculation and vehicle kinematics, relevant collision severity parameters are calculated. These steps are executed in an own developed standalone tool named impactEES. The results obtained were verified against measured crash test data from the European New Car Assessment Programme (Euro NCAP) and the Technical Center of Allgemeiner–Deutscher–Automobil-Club (ADAC). Results: The novel method enables the automated computation of various car-to-car and car-to-object collisions. The output of impactEES includes the deformation area, EES, and delta-v. Furthermore, it includes the following time-discrete data for each vehicle: translational and angular accelerations, translational and angular velocities, and the position of the center of gravity in addition to the heading of the vehicle. Finally, without the need of highly sophisticated hardware, a single simulation of a collision between two vehicles can be calculated within only a few seconds including collision severity parameters. Based on the comparison of measured crash test data and results obtained from impactEES the mean percentage error (MPE) and its standard deviation (SD) were calculated for EES (MPE= − 2.0%, SD = 8.4%, n = 14) and delta-v (MPE= − 1.2%, SD = 14.2%, n = 18). Conclusions: The novel method allows for the 2 D computation of various car-to-car and car-to-object collisions. Using predefined IRF allows the assessment of injury probabilities relative to the change of collision severity parameters. Both can be used for the virtual assessment of injury mitigation capabilities of active safety systems and thus represent an important contribution to its targeted development. [ABSTRACT FROM AUTHOR]

Pedestrians who use wheelchairs (seated pedestrians) report 36% - 75% higher mortality rates than standing pedestrians in car-to-pedestrian collisions but the cause of this mortality is unknown. This is the first study to investigate the cause of seated pedestrian mortality in vehicle impacts using finite element simulations. In this study a manual wheelchair model was developed using geometry taken from publicly available CAD data, and was tested to meet ISO standards. The GHBMC 50th percentile male simplified occupant model was used as the seated pedestrian and the EuroNCAP family car and sports utility vehicle models were used as the impacting vehicles. The seated pedestrian was impacted by the two vehicles at three different locations on the vehicle and at 30 and 40 km/h. In 75% of the impacts the pedestrian was ejected from the wheelchair. In the rest of the impacts, the pedestrian and wheelchair were pinned to the vehicle and the pedestrian was not ejected. The underlying causes of seated pedestrian mortality in these impacts were head and brain injury. Life-threatening head injury risks (0.0% - 100%) were caused by the ground-pedestrian contact, and life-threatening brain injury risks (0.0 - 97.9%) were caused by the initial vehicle-wheelchair contact and ground-pedestrian contact. Thoracic and abdominal compression reported no risks of life-threatening injuries, but may do so in faster impacts or with different wheelchair designs. Protective equipment such as the wheelchair seatbelt or personal airbag may be useful in reducing injury risks but future research is required to investigate their efficacy. [ABSTRACT FROM AUTHOR]

The present research aims to understand the safety over the midblock road sections and proposes a safety framework using the conventional Time to Collision (TTC) measure. In the present work, the safety framework underlines a supporting structure connecting the actions of the surrounding vehicles and assesses the collisions changes for a given subject vehicle. The Framework principally checks the likelihood of lateral overlap and the time gap between the subject vehicle and its surrounding vehicles. Later, for the trajectory data development, an automated trajectory data development tool is built with the help of image processing for generating the trajectory data from the study sections. In supporting the developed safety framework, the lateral movement of the vehicles is modeled precisely with the help of deep learning. Further, the conceptualized safety framework is tested with the developed trajectory data sets over the study sections. From the results, it is observed that, in mixed traffic, the collision points are over the entire geometry of the study section. In the case of homogeneous traffic, the collision instincts are clustered toward the median lanes. With the advancement of technology, trajectory data development can be a real-time exercise, and the safety framework can be implemented. By applying the study methodology, the critical spots over the road network can be flagged for better treatment and improve safety over the sections. [ABSTRACT FROM AUTHOR]

In this work, we report a novel controller to solve (globally) the position and orientation consensus-based formation problem of multiple nonholonomic vehicles modelled as differential drive robots affected by external disturbances. The controller has the structure of a simple to implement Proportional Integral Derivative (PID) scheme. In order to satisfy the well-known Brocket stabilisation theorem for nonholonomic systems, we also incorporate a time-varying persistency of excitation term in the angular velocity dynamics. Our proposal reports the first solution to the robust formation problem using a smooth time-varying controller. Simulations are shown to evidence the theoretical findings of this work. [ABSTRACT FROM AUTHOR]

Under the trend of promoting economy, environmental protection and high efficiency in the urban rail transit industry, this paper proposes a new type of straddle-type rapid transit system. Compared with most straddle-type monorail systems, it has the advantages of low construction cost and low operating cost, which makes it more suitable for urban rail transit system in small and medium-sized cities. In the process of vehicle development and design, in order to achieve the coordination and matching of tire systems and reduce the wear of tire systems, this work uses a multi-objective optimisation method to reduce the guiding torque of each tire system when the vehicle passes through the curve. Based on the vehicle dynamics model, the multi-body dynamics simulation model of the vehicle is established. The guiding torque of each tire system is taken as the optimisation objective, and the position and dynamic parameters of each tire system are taken as the optimisation parameter. Based on the NSGA-II algorithm, the ISIGHT and SIMPACK software are used for co-simulation. Finally, the guiding torque of each tire system is effectively reduced, and the coordination and matching of tire system is realised. [ABSTRACT FROM AUTHOR]

This investigation integrates an alternative fully-parameterized approximation of nonlinear wheel/rail interaction into a simplified vehicle model, and a two-parameter Hopf bifurcation analysis is conducted to reveal the influence of the wheel/rail contact geometry and secondary suspension parameters for high-speed rail vehicles. The bifurcation diagram is compared among the 6 DOFs bogie model, linear and nonlinear 7 DOFs vehicle model, nonlinear 17 DOFs vehicle model, and 3D full DOFs vehicle model. It shows that the nonlinear 7 DOFs vehicle model can meet the requirement of both carbody hunting and bogie hunting simulations. 6 DOFs bogie model can only be used in bogie hunting bifurcation analysis. Linear vehicle model would bring errors in either critical speed or limit circle magnitude. The divergences in the linear terms of rolling radius and contact angle polynomials are significant enough in field operation to cause a noticeable difference in Hopf bifurcation speed. Attention shall be paid to the shape of equivalent conicity and contact angle curve. The crucial parameters to the Hopf bifurcation include the series stiffness and damping coefficient of the yaw damper and the lateral damper damping. However, the requirement of suspension parameters for stability can conflict in carbody hunting and bogie hunting cases. [ABSTRACT FROM AUTHOR]

This study investigates the impacts of the sharing economy and vehicle automation on household vehicle ownership by considering the earning potential of household vehicles. While many studies have examined the impact of the sharing economy (namely ridesourcing) on vehicle ownership of ridesourcing customers, there is a gap in understanding its impact on vehicle ownership among ridesourcing suppliers. Data from an original survey are used to develop discrete choice models that evaluate the effects of earning potential, automation, and shared autonomous vehicle services on vehicle transaction decisions. The estimated models are applied to perform national-level simulations. It is found that, in comparison to a non-sharing economy context, individuals in the sharing economy tend to purchase more vehicles in times of income gain, and to preserve their fleets more readily in times of income loss. This study provides evidence that the sharing economy incentivizes some individuals to own more – not fewer – vehicles.. [ABSTRACT FROM AUTHOR]