Vehicle Deceleration Research Articles

Influence of Drivetrain Hybridization on Transmission Lifetime

Parallel hybrid drivetrains for passenger cars have additional electric drives compared to conventional drivetrains. In the event of vehicle deceleration, the electric drives are operated as generators, thus recovering kinetic energy through regeneration. If these drives are positioned upstream of the transmission input, regeneration power must be transferred by the transmission. This creates additional loads on the individual machine elements, which has a negative effect on the transmission lifetime. This paper investigates the influence of hybridization in terms of regeneration on the lifetime of bearings as highly critical elements in a dual clutch transmission. The vehicle simulation model employed in this study consists of an internal combustion engine, an electric motor, a mechanical drivetrain and the vehicle body, as well as a driver and a simple operating strategy. In this model, a detailed transmission model including its controls is embedded to determine its component loads. The resulting load spectra are used in a methodical approach to calculate the bearing lifetime of the transmission. The results show that the additional regenerative power flow reduces the bearing lifetime so that additional loads must be taken into account in the development and operation of transmission systems.

An examination of the performance of damaged energy-absorbing end terminals

ObjectivesGuardrail end terminals are designed to gradually decelerate vehicles during impact and protect vehicle occupants from severe injuries. It has been observed that some in-service end terminals are damaged, and it is unclear if their safety performance is still acceptable. The objectives of this study were to examine the conditions of in-service end terminals, and to evaluate the performance of damaged relative to undamaged end terminals in simulated impacts. MethodsCommon damage patterns of guardrail end terminals were investigated by using post-crash pictures collected from the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS). Conditions of in-service end terminals mounted along roads in portions of six U.S. states were examined by using a sample from the second Strategic Highway Research Program-Roadway Information Database (SHRP2-RID). Finite Element (FE) models of two minorly and three severely damaged ET-Plus systems, a commonly used energy-absorbing guardrail end terminal along U.S. roads, were developed. To evaluate the performance of the damaged ET-Plus systems, we performed impact simulations with vehicle-to-damaged ET-Plus models according to the National Cooperative Highway Research Program (NCHRP) 350, test conditions 3–30. ResultsOf the 1000 in-service end terminal cases we investigated, 73% were undamaged, 18% had minor damage, and 8% had major damage. Increases in the average vehicle deceleration rates, maximum vehicle yaw angles, and vehicle local deformations were observed in simulated impacts with damaged ET-Plus end terminals relative to impacts with undamaged ET-Plus end terminals. For one damaged ET-Plus, a secondary collision was observed. Overall, we found that the damaged end terminals usually increased collision severity when compared with undamaged end terminals. ConclusionsThe findings of this study point out the need for in-service performance evaluations and proper maintenance and repair practices of end terminals. The simulation models developed in this study could be further employed to investigate device performance in crash situations that are physically impractical to test and investigate the effects of site characteristics on device performance. The simulation models could also supplement crash tests to certify new hardware designs.

Concentrations of selected trace elements in surface soils near crossroads in the city of Bratislava (the Slovak Republic).

It is well known that road transport emits various trace elements into the environment, which are deposited in soils in the vicinity of roads, so-called roadside soils, and thus contributes to the deterioration of their chemical state. The aim of this work was to determine concentrations of some metals and metalloids (arsenic (As), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), antimony (Sb), vanadium (V), and zinc (Zn)) in soils from crossroads with traffic signals, which are characterized by deceleration of vehicles and increased emissions of elements related mainly to brake and tyre wear. The results confirmed a moderate enrichment of soils with Cu, Pb, and Zn (enrichment factor (EF) values > 2) and significant enrichment for Sb (EF > 5), while the other elements showed no or minimal enrichment. The age of crossroads proved to have a positive influence on the accumulation of some elements in soils with the largest differences for Cu, Fe, Pb, Sb, and Zn (p < 0.001). Traffic volumes expressed as the average daily traffic intensity (ADTI) also positively influenced soil concentrations of Cr, Cu, Pb, Sb, and Zn, while distance to the crossroad had a significant negative effect on the soil concentration of Cu, Sb, and Zn (p < 0.001). The stable isotopic ratios of Pb, 206Pb/207Pb and 208Pb/206Pb, ranging from 1.1414 to 1.2046 and from 2.0375 to 2.1246, respectively,pointed to the mixed natural-anthropic origin of Pb in the soils of crossroads with a visible contribution of traffic-related sources. Based on the above findings combined with covariance among the studied elements using statistical methods applied to compositionally transformed data, it was possible to show that Cu, Pb, Sb, and Zn clearly originated from road traffic.

Evaluation and Optimization of Responsibility-Sensitive Safety Models on Autonomous Car-Following Maneuvers

Safety is an important challenge in the development of autonomous vehicles (AVs). To ensure the safety of AVs, Intel and Mobileye have proposed a model called Responsibility-Sensitive Safety (RSS). Previous studies have shown that RSS has the potential to improve the safety performance of AVs, especially for partial autonomous driving algorithms. However, it is been shown that RSS leads to a considerable car-following distance, which has a negative effect on traffic efficiency. To improve the efficiency of RSS when applied to adaptive cruise control (ACC) systems, this paper proposes an improved strategy that involves triggering conditions of RSS. Two triggers of safety distance are defined according to different car-following assumptions. To test the performance of RSS models, original and improved RSS models are embedded in ACC based on model predictive control (MPC) algorithms. Car-following scenarios with a sudden deceleration of the lead vehicle (LV) at various time headways are simulated to evaluate the performance of improved RSS models. Results show that triggering RSS at the boundary of the safety distance calculated by considering the vehicle’s intentions is a better RSS model. This improved RSS model has a similar safety improvement effect to the ACC system as the original RSS in most risk scenarios and performs better in car-following efficiency. As the improved RSS model achieves a better trade-off between safety and efficiency, it can be used to improve the safety performance of partial autonomous driving algorithms like ACC on autonomous car-following maneuvers on expressways.

Three-dimensional discrete element simulation of the runaway vehicle deceleration process on the arrester bed of truck escape ramps.

Due to imperfect design norms and guidelines for China's truck escape ramp, previous studies have not been able to reflect the effect of wheel subsidence process on the deceleration of runaway vehicles. A discrete element method was used to establish an aggregate discrete element and a wheel discrete element. The three-dimensional discrete element model for an aggregate-wheel combination was established based on a particle flow code in three dimensions on a software platform using the "FISH" language. The microscopic parameters of the aggregate discrete element particles and wheel discrete element particles were calibrated using a simulated static triaxial compression test and real vehicle test data, respectively. Four sets of numerical simulation tests were designed for analyzing the influence of the aggregate diameter, grade of the arrester bed, truckload, and entry speed on the wheel subsidence depth and stopping distance of runaway vehicles. The results indicate that the smaller the aggregate diameter and entry speed and the greater the truckload and grade of the arrester bed, the more easily the wheel falls into the gravel aggregate, the better the deceleration effect, and the smaller the stopping distance. As the wheel subsidence depth increases, the speed at the unit stopping distance decreases more quickly. The maximum subsidence depth mainly depends on the truckload. The research results can provide a theoretical basis for the design of the arrester bed length and the thickness of the aggregate pavement in a truck escape ramp.

Study on the improvement of the vehicle deceleration signalling system

Our paper presents a study regarding the improvement of the vehicle deceleration light signalling system. Based on global statistics on the number of road accidents caused by non-compliance with the safety distance and a market research on the availability of purchasing an extra option to allow drivers to be informed about the speed reduction of the vehicle in front, we have applied the Product Life Cycle Management (PLM). For this purpose, we made two market researches. Based on the results of the primary market research and the technical solutions currently in place, a new market research was carried out through an opinion poll. All the results of the opinion polls were discussed in a brainstorming session, which was attended by representatives of automotive companies, representatives of academia and professional drivers. At the end, we have demonstrated the possibility of developing a new product that aims to reduce road accidents caused by rear-end collisions. The working method, proposed has led to the need to find new constructive solutions and ways to apply them.

Tyre-Road friction Coefficient: Estimation Adaptive System

This paper offers an upgraded method for estimating the magnitude of friction between tyres of a motor vehicle and a road surface while investigating road accidents. The above-mentioned method is based on the resultant data of tyre-and-road interworking field tests in case of emergency braking. Such estimation of the magnitude of friction is to be carried out with a focus on the factors affecting the friction processes in the tyreand-road contact. The most important factors, which are included in the synthesized adaptive system used for friction coefficient estimation, have been defined based on the theoretical analysis of the data of deceleration and braking length of motor vehicles. The study of the existing expert methods used for estimating the level of tyre-and-road engagement and the effect of such level on the motional parameters of a motor vehicle has demonstrated the need for upgrading of the existing approaches. Unlike the existing practices, the friction coefficient estimation adaptive system offered by the authors hereof is a self-trainable system. Such system reduces any simulation uncertainty and the probability of occurrence of Type 1 and Type 2 errors. Such result is achieved owing to the fact that the system takes into account the upgraded design of the present-day brake systems and tyres, as well as the speed of motor vehicles and load of their wheels; the system is also efficient because it makes use of the up-to-date mathematical methods which are able to process raw (initial) data under conditions of stochastic and fuzzy uncertainty. The approach offered hereby has demonstrated its efficiency for motor vehicles belonging to categories М1 and N1 and has proven its potential applicability for other categories of motor vehicles.

Spatiotemporal trajectory characteristic analysis for traffic state transition prediction near expressway merge bottleneck

The theoretical analysis of traffic flow with empirical vehicle trajectory data contained within this study allows for the explanation, reconstruction, and prediction of spatiotemporal transition characteristics of traffic conditions. Using an unmanned aerial vehicle (UAV) during a morning rush hour on a working day, observations of congestion evolution near an on-ramp bottleneck of an expressway was captured. The empirical high-fidelity trajectory data of 621 vehicles were extracted. The major findings include:(1) Macroscopic perspective: Three traffic states (free flow, metastable traffic flow, and jam) were observed with different spatiotemporal physical structures and their critical characteristics in a continuous first-order phase transition. The spontaneous spatiotemporal traffic breakdown and capacity drop were also captured, the critical points of which were also recorded. The features of widening synchronized flow pattern, general pattern, and the nature of nucleation described in the three-phase traffic theory were identified, which provides a new observational cognition for congestion formation and development.(2) Microscopic perspective: The impact of lane changes on immediate vehicles were modeled and quantified with the fluctuation magnitude of speed and the theoretical lag distance, which provides a method to identify the source of perturbation and determine the microscopic critical threshold of vehicle between macroscopic phase transitions. The research shows a lane changer could cause a forced deceleration of an immediate vehicle on a target lane after inserting itself with critical spacing headway below approximately 15–20 m. The average deceleration duration of vehicles in different traffic states can be captured as crucial driving features from downstream to help predict traffic state transition in a real bottleneck.

Before–After Evaluation of Left-Turn Lane Extension Considering Injury Severity and Collision Type

Left-turn lanes are commonly used to provide space to accommodate vehicle deceleration and provide adequate storage of turning vehicles. The objective of this study is to evaluate the safety effectiveness of extending the length of left-turn lanes at signalized intersection approaches. Five years of collision data including injury severity and collision type from three treatment sites and 31 comparison sites in the City of Surrey, Canada were used in the study. The analysis focused on target crashes including left-turn-related rear-end and left-turn-related sideswipe collisions. A full Bayesian (FB) before–after analysis was conducted for all collisions, severity levels, and collision types. Multivariate Poisson–lognormal linear intervention models were used for the analysis. The treatment effectiveness index was calculated to quantitatively measure the effectiveness of the safety treatment. The FB before–after results showed that the treatment-related collisions were reduced by 57.4% following the implementation of extended left-turn lane. The reduction in injuries and fatalities collisions (63.8%) was greater than that in property damage only collisions (55.7%). The decrease in rear-end collisions (62.8%) was greater than that in sideswipe collisions (58.1%). The findings indicate a remarkable improvement in safety after the length extension of the left-turn lane.

Optimal merging into a high-speed lane dedicated to connected autonomous vehicles

In the future, High Occupancy Vehicle (HOV) lanes or other dedicated lanes might be restricted to autonomous vehicles, e.g wirelessly connected vehicles with longitudinal motion control. These vehicles would likely travel at high speeds in platoons. New criteria for the merging of a vehicle from an adjacent freeway are proposed. To reduce disruption to the flow, only merges into gaps between platoons, not within, are considered. To minimize HOV lane trip time and vehicle deceleration, the optimal merge position is determined from simulations of linear combinations of the deviation of the headway from equilibrium and vehicle velocity differences. These are between the merging vehicle and the trailing vehicle (on the HOV lane) and the merging vehicle and the last vehicle of the preceding platoon. The merging vehicle, due to acceleration limitations on the freeway, generally will merge at a significantly lower velocity than the HOV lane average velocity.

System-Level Reliability Analysis of Cooperative Driving with V2X Communication for Intersection Collision Avoidance

Cooperative driving with vehicle-to-everything (V2X) communication is a promising technique to improve traffic safety and efficiency. Intersection collision avoidance (ICA) is a typical safety application of it. This paper analyzes reliability of ICA with cooperative manual driving at the system level. First, the reliability of an ICA system is defined as the probability of the ICA system avoiding collisions or near-misses at intersections without failure under conditions that collisions or near-misses are about to happen. Post-encroachment time is used in the expression of this definition. Then, components of the ICA system are classified into four types: hardware, software, maneuver, and V2X communication, and a reliability block diagram (RBD) is applied to reveal how these components contribute to system reliability. Five ICA system patterns with different V2X communication modes and strategy types are compared based on RBD analysis. This shows that centralized strategies are more reliable than decentralized ones for V2I communication if software reliability of these two strategies is the same. Furthermore, reliabilities of ICA components are analyzed in detail, and they are classified into two categories based on their different impact modes on the system. Finally, a numerical example shows how to test reliability of an ICA system using reliabilities of its components by Monte Carlo simulation. Results show that closer distances from vehicles to their conflict point when alerted, longer driver reaction time, and smaller vehicle deceleration rates are more likely to lead to system failure, whereas communication latency has little effect on it.

Experimental strategy to determine nitrogen catalytic behavior of high‐temperature woven ceramics

AbstractNew vehicle deceleration strategies have led to the development of deployable thermal protection systems with woven fabric outer layers that can withstand the harsh aerothermal environment of planetary entry. In this work, we present an experimental strategy for testing fabric samples and a method to determine nitrogen catalytic efficiency, γN, from two‐photon laser‐induced fluorescence measurements of recombining nitrogen atoms near the sample surface. Measurements were made on other silicon carbide materials to better understand the influence of the fabric structure and porosity on catalytic recombination. The three test materials studied were a monolithic α‐SiC, a CVD β‐SiC, and a single‐ply, Hi‐Nicalon β‐SiC fabric layup. Extracted catalytic efficiencies for atomic nitrogen recombination for monolithic α‐SiC, CVD β‐SiC, and single‐ply β‐SiC fabric are (6.18 ± 1.55) × 10−4 (at 1460 K), (3.59 ± 0.90) × 10−3 (at 1500 K), and (8.34 ± 2.19) × 10−4 (at 1675 K), respectively. This would categorize these materials as low‐catalytic materials for nitrogen atom recombination in this temperature range.

Selection of the required deceleration for high-mobility wheeled vehicles with wear resistant brake systems

Analysis of the driving cycles of the high-mobility wheeled vehicles shows that the driver tries to provide a high speed when performing maneuvers. This results in high loads both on the powerplant and the brake system. During quick changes of the driving modes, the service brake system has to dissipate a lot of energy, which may cause overheating of its working elements and changes (deterioration) in their frictional properties or their increased wear, or even a failure of the system. The article reveals the method for selection of the required deceleration of high-mobility wheeled vehicles with wear resistant brake systems providing higher speeds and considerably lower loads on the service brake system and increased life of the frictional elements. The method is based on the generation of the driving cycle, which is close to the real-life operation conditions of the high-mobility wheeled vehicles with the use of stochastic data on the roads. Thus, driving conditions are described as realizations of random functions of such external factors as the trajectory curvature, the friction coefficient between the tire and the road, and the tire rolling resistance coefficient. The driving cycle is generated with allowance for the vehicle stability, the powerplant performance, the physiological capability of the driver to withstand accelerations, and the maximum available deceleration. By varying the vehicle deceleration we can find the dependence of the vehicle average speed on its deceleration. The data obtained during the analysis helps to select the deceleration which can be effectively provided by the wear resistant brake system without the use of the service brake system. A method for selection of the wear resistant brake system characteristics with the use of stochastic data on the driving conditions. The method allows selection of the torque – speed curves of the units of a wear resistant brake system providing required mobility of the vehicle.

Comparative assessment of vehicle anti-lock braking system operation using friction brake mechanisms and e-machine in the vehicle with electric drive of traction wheels

Study of the braking process of the vehicle with an electric machine in the traction wheels drive equipped with an anti-lock braking system (ABS), where the actuators are the electric machine and friction brake mechanisms, is a relevant task. This is related to the worldwide trending increase in the share of production of vehicles with an electric machine within the transmission. In this paper, the “traditional” ABS and two systems with different variants of usage of the electric machine and friction brake mechanisms as actuators are compared: 1. The electric machine fulfills the function of the wheel slip regulator; the friction brake mechanisms maintain constant pressure in the brake line, which depends on the tyre-road friction coefficient. 2. The friction brake mechanisms fulfill the function of the wheel slip regulator; the electric machine maintains the set brake torque. According to the study results, usage of the combined actuator system within the ABS allows reducing the braking distance significantly, raising the vehicle deceleration value and improving the driver’s and passengers’ comfort during braking.

A New Safety Distance Calculation for Rear-End Collision Avoidance

Rear-end collision avoidance relies on mathematical models to calculate the safety distance. Vehicle deceleration is a key parameter for the accuracy of the models. Current models, however, assume a constant deceleration during braking, which is unrealistic. This assumption results in large over-approximation / under-approximation. In this paper, we rectify this limitation by proposing a new model that accounts for realistic vehicle deceleration during braking. Simulation results show that our approach guarantees safety. Moreover, traffic flow is improved by 21.6% compared to the widely adopted the Berkeley algorithm.

Improving the quality of the investigation of a road traffic accident

The article deals with the issue of improving the quality of auto expertise and as a result, with the issue of investigating road accidents. The main parameter used in the auto expertise is vehicle deceleration. But today we consider the characteristics of the roadway and the load of the car when decelerating a car. As for temperature factor it is not only ignored, but the possibility to take it into account doesn’t even exist. The impact of the ambient temperature on vehicle deceleration was studied. There was simulation of vehicle braking which physically justified the impact of ambient temperature. On the basis of the practical tests conducted, the dependence of vehicle deceleration on the ambient temperature was determined. This dependence will allow auto experts make calculations more objectively which will positively affect not only the course of road accident investigation but also the identification of factors conducive to development and emergence of the accident.

The influence of the cargo weight and its position on the braking characteristics of light commercial vehicles

AbstractThe influence of the cargo weight loaded on the vehicle and the total gross mass of the vehicle on the braking characteristics is often researched from the road safety reason. However, there is not enough knowledge about the influence of weight and load distribution on the loading area of small trucks or vans on their braking characteristics. This article presents the results of measurements of braking decelerations of the van of N1 category and the braking characteristics of a vehicle loaded with different cargo mass with different cargo locations on the loading area. The impact of the longitudinal cargo position on the loading area on the load of the individual axles and thus on the braking deceleration of the vehicle was investigated. The influence of the height of the center of gravity on the dynamic axle load during braking was also determined. Method of direct vehicle deceleration measurement was used by a decelerometer. There were calculated cargo weight and cargo position influences on the dynamic axle load during braking according to the vehicle deceleration.

Decelerations of Passenger Vehicles on Gravel Arrester Beds

Gravel-filled arrester beds, also called safety-escape ramps or vehicle run-out areas, have long been a road-safety feature for safely stopping heavy road vehicles from running off the road. In the recent past, there has been consideration given to installing these features on highway access ramps to provide safe areas to stop passenger cars driving at highway speeds. The work presented in this article was performed to investigate the behaviour of standard-size passenger cars on gravel-filled arrester beds, with a particular focus on the achievable vehicle decelerations and the ability of the arrester beds to safely stop a passenger car coasting in an uncontrolled manner. The findings show that the achievable average decelerations are in the range of 0.3 g for coasting vehicles and up to 0.9 g when the vehicles are braking. The results prove that more research is required to quantify the influence of the gravel parameters on the achievable decelerations.

ВПЛИВ ЗМІНИ КОНСТРУКЦІЇ МОТОЦИКЛА НА ПАРАМЕТРИ ГАЛЬМУВАННЯ ТА ЗВАЖАННЯ НА НИХ ПІД ЧАС АВТОТЕХНІЧНОЇ ЕКСПЕРТИЗИ

Мета статті – виявити чинники, які впливають на зміну усталеного сповільнення мототранспортних засобів у процесі вдосконалення їх гальмової системи, окреслити проблеми невідповідності статистичної бази даних сповільнення автотранспортних засобів, яку судові експерти використовують для розрахунків у межах автотехнічної експертизи, та параметрів сповільнення сучасних мототранспортних засобів, що постали внаслідок постійного вдосконалення їх гальмових систем, і, відповідно, зміни параметрів гальмування. У процесі дослідження обґрунтовано необхідність вжиття додаткових заходів для отримання достовірних даних. Акцентовано увагу, оскільки натепер автотранспортний ринок представлений мототранспортними засобами з класичною застарілою конструкцією гальмової системи (механічною) і сучасною (гідравлічною, комбінованою тощо), на конструкції цих гальмових систем, здійснено їх порівняння, виокремлено їх переваги та недоліки. Доведено доцільність доповнення та подальшого методичного розвитку статистичної бази даних параметрів сповільнення мототранспортних засобів, зважаючи на зміни, що відбулися в гальмових системах. Достовірність отриманих результатів і висновків забезпечено системою методів наукового пізнання. Серед них, зокрема, синтезу та аналізу, у тому числі статистичного – для підвищення точності та об’єктивності, а отже якості експертних висновків, обґрунтування необхідності комплексних випробувань із метою отримання реальних значень сповільнення сучасних мототранспортних засобів.Ключові слова: судові експерти; сповільнення мотоцикла; дискові гальма; гідравлічний привід гальм; гальмова колодка; накладки; система ABS.

Mobile Phone Use in a Car-Following Situation: Impact on Time Headway and Effectiveness of Driver's Rear-End Risk Compensation Behavior via a Driving Simulator Study.

Mobile phone use while driving has become one of the leading causes of traffic accidents and poses a significant threat to public health. This study investigated the impact of speech-based texting and handheld texting (two difficulty levels in each task) on car-following performance in terms of time headway and collision avoidance capability; and further examined the relationship between time headway increase strategy and the corresponding accident frequency. Fifty-three participants completed the car-following experiment in a driving simulator. A Generalized Estimating Equation method was applied to develop the linear regression model for time headway and the binary logistic regression model for accident probability. The results of the model for time headway indicated that drivers adopted compensation behavior to offset the increased workload by increasing their time headway by 0.41 and 0.59 s while conducting speech-based texting and handheld texting, respectively. The model results for the rear-end accident probability showed that the accident probability increased by 2.34 and 3.56 times, respectively, during the use of speech-based texting and handheld texting tasks. Additionally, the greater the deceleration of the lead vehicle, the higher the probability of a rear-end accident. Further, the relationship between time headway increase patterns and the corresponding accident frequencies showed that all drivers’ compensation behaviors were different, and only a few drivers increased their time headway by 60% or more, which could completely offset the increased accident risk associated with mobile phone distraction. The findings provide a theoretical reference for the formulation of traffic regulations related to mobile phone use, driver safety education programs, and road safety public awareness campaigns. Moreover, the developed accident risk models may contribute to the development of a driving safety warning system.