Society Of Automotive Engineers Research Articles

A Comprehensive Investigation into Bidirectional DC-DC Converters with Soft Switching for Electric Vehicles

Electric vehicles (EVs) are one of the the promising solutions for the environmental issues such as carbon emission and global warming. The high voltage traction battery in EVs is charged from utility grid by an EV charger. The Society of Automotive Engineers (SAE) standardize EV charges into two categories on-board chargers and off-board chargers. Usually, the on-board chargers are located inside the vehicle whereas, off-board chargers are not mounted on the vehicle. For onboard chargers, size and power density of charger become a prior matter of concern. The only way to reduce the size of a converter and thereby increase the power density is to operate power electronic conversion system (PECS) at very high switching frequency (HSF) resulting in reduced size of magnetic component in the charger configuration. However, HSF operation may lead to a high electromagnetic interference (EMI), loss in switch and switch duty. The work in this paper is focused on the development of high frequency bi-directional DC-DC converter (BD2C) stage priory used in on-board chargers due to distributed sources of energy as well as to manage the power distribution in the configuration. The power electronic BDCs are derived from boost and buck unit. The boost derived converter are current fed converters and offers advantages in terms of inherent voltage gain, short circuit protection and lower input current ripple. The voltage spikes across switches, high rated device selection, hard switching, snubber and auxiliary circuit requirements are some of the undesirable factors. This occurrence happened due to unbalance power transfer by the power electronics converter. Similarly, voltage fed converter offers good voltage control during power transfer.

Influence of Quenching and Tempering on the Tribological and Corrosion Behavior of Plasma‐Nitrided Society of Automotive Engineers 52100

Society of automotive engineers (SAE) 52100 (100Cr6) steel, used in manufacturing bearings and shafts, deserves attention due to wear and corrosion problems that cause machine losses in the industry. To solve these problems, heat treatments such as quenching and tempering are adopted to reduce wear mechanisms. However, in this work, the effect of these previous heat treatments on the final properties of plasma nitrided steel at three different temperatures (400, 450, and 500 °C) is evaluated. Surface hardness, tribological behavior, and corrosion resistance are evaluated. In the results of Vickers hardness, wear, and electrochemical analysis, it is shown that performing plasma nitriding at 400 and 450 °C on previously heat‐treated SAE 52100 steel provides better mechanical resistance and chemical integrity in a corrosive environment, making the studied steel more comprehensive for important industrial applications.

Enhancing oil pressure dynamics in a high-performance racing engine with innovative lubrication system tuning

This work focuses on fine-tuning the oil pressure dynamics of a single-seater formula car, a participant in international engineering competition organized by the Society of Automotive Engineers (SAE). Adhering to competition guidelines, the Honda CBR600RR 05-06® motorcycle engine, renowned for its 600 c.c. displacement and exceptional power-to-weight ratio, emerges as a popular choice. However, as this engine is originally equipped with a wet sump lubrication system (featuring deep wet sumps to prevent oil starvation during turns), this presents challenges when adapted to Formula Society of Automotive Engineers (FSAE) cars. Cornering leads to significant pressure drops, as sloshing exposes the pickup port, causing consequential engine issues. To tackle sloshing-related challenges and pressure loss during lateral and longitudinal g-forces, a dry sump lubrication system was introduced in the Formula car. The dry sump system also lowers the engine’s center of gravity, by reducing sump height. However, transitioning to the dry sump system and integrating it with the existing engine demanded extensive design modifications to various components, including the oil reservoir, lubrication lines, scavenging pump, and oil ports. These adjustments were essential to achieve the targeted elevation in oil pressures at higher engine RPMs. A relationship between the engine oil pressure and the engine RPM was developed as part of the study.

Preface

The ESFA Congress is a part of a series of SIAR (Society of Automotive Engineers from Romania) congresses which are organized annually, by rotation, in Romanian universities that train engineers in the field of Automotive Engineering (Bucharest, Brașov, Pitesti, Craiova, Cluj, Chisinau, Timișoara). This congress is the 33rd edition of the SIAR Congress.The ESFA Congress are hosted by National University of Science and Technology POLITEHNICA Bucharest, the oldest and most prestigious engineer school from Romania. These congresses are organized by the Automotive Engineering Department since 1981, being one of the scientific events with great visibility among specialists in the field of Automotive Engineering.According to the organizers’ expectations, more than 150 Romanian specialists and from other countries, renowned companies involved in various activities specific to the field of automotive engineering, participated in this congress.The Congress provided optimal conditions for the presentation of the latest achievements of scientific and technological research in the automotive industry and automotive components, in the field of vehicle maintenance and road transport, and facilitated the exchange of information and experience between participants.One of the main purposes of the congress was to promote and present the most modern products and current technologies in the field of automotive engineering from the most prestigious romanian companies and abroad. For this purpose, exhibitions (indoor and outdoor), demonstrations, experimental tests, appropriate software presentations etc. were organized within the congress.On the occasion of the SIAR congress, the final stage of the Student Competition in Automotive Engineering “Prof. university Eng. Constantin GHIULAI” is organized annually by SIAR, with two sections: Vehicle Dynamics (nineth edition) and Automotive CAD - CATIA (sixth edition).About of 70 students from almost all Romanian university centers which have studied programs in the field of Automotive Engineering participated in the final stage of this competition.ESFA 2023 Proceedings EditorsList of Honorary Committee, Scientific and Technical Committee, Congress Management, Organizing Committee, Brief overview of ESFA 2023 Congress, Oral presentations of scientific papers by sections, Exhibition, Aknowledgements are available in this pdf.

Coil Parameter Analysis for Inductively Coupled Wireless Charging for Electric Vehicles

Wireless charging (WC) has gained popularity for the charging of electric vehicles in recent years of research, particularly dynamic wireless charging systems (DWCSs). Among the different topologies of DWCSs, this paper focuses on an inductively coupled wireless charging system (ICWCS). In this ICWCS, double-D (DD) coils create horizontal and vertical flux components between different pad configurations, which show optimal features in contrast to circular pad coils. In this work, the three-dimensional (3D) finite element technique (FEM) is used to establish the proposed design to observe the coupling coefficient, while the system design’s performance is evaluated using a circuit simulator. In the simulation, the proposed DD coil configuration is used for both the transmitter and receiver sides. It provides the maximum coupling coefficient and efficiency at perfect alignment when using an in-between air gap of 166 mm and six I-type ferrite bars on the transmitter side and five I-type ferrite bars on the receiver side. The coupling coefficient and system parameters, such as power and efficiency, are considered for different misalignments in the proposed configuration. The results of this work satisfy the Society of Automotive Engineers (SAE) J2954 Class 3 criteria. The best results obtained are on account of optimizing the ferrite core, which is achieved by varying its length and width. While varying the ferrite core’s dimensions, 0.2451, as the optimal k value, is obtained at the effective width and length of 57.5 mm and 400 mm, respectively. The simulation results of the Ansys Maxwell 3D software prove the feasibility of the proposed structure.

Choosing Optimal Cutoff Frequencies for Filtering Linear Acceleration and Angular Velocity Signals Associated with Head Impacts Measured by Instrumented Mouthguards

Head impact sensors worn in the mouth are popular because they couple directly to the teeth and provide six-degree-of-freedom head measurements. Mouthpiece signal filters have conventionally used cutoff frequencies lower than recommended practices (Society of Automotive Engineers, SAE J211-1) to eliminate extraneous noise when measuring with live subjects. However, there is little information about the effects of filter choice on the accuracy of signals measured by instrumented mouthpieces. Lack of standardization in head impact measurement device post-processing techniques can result in data that are not comparable across studies or device brands. This study sought optimal filter cutoff frequencies for six-degree-of-freedom measurements made at the teeth using instrumented mouthguards. We collected linear acceleration and angular velocity signals at the head center of gravity (CG) using laboratory-grade instrumentation. We also collected and filtered similar six-degree-of-freedom measurements from an instrumented mouthguard using 24 cutoff frequencies, from 25 to 600 Hz. We transformed the measurements to linear acceleration at the center of gravity of the head (CG) using all kinematic variables at the teeth, optimizing linear and angular mouthguard cutoff frequencies with one equation. We calculated the percent error in transformed peak resultant linear acceleration and minimized the mean and standard deviation in error. The optimal cutoff frequencies were 175 Hz for linear acceleration and 250 Hz for angular velocity. Rigid impacts (3–5 ms duration) had higher optimal cutoff frequencies (175 Hz linear acceleration, 275 Hz angular velocity) than padded impacts (10–12 ms duration; 100 Hz linear acceleration, 175 Hz angular velocity), and all impacts together (3–12 ms duration; 175 Hz linear acceleration, 250 Hz angular velocity). Instrumented mouthpiece manufacturers and researchers using these devices should consider these optimal filter cutoff frequencies to minimize measurement error. Sport-specific filter criteria for teeth-based sensors may be warranted to account for the difference in optimal cutoff frequency combination by impact duration.

Human-centered design and evaluation of a workplace for the remote assistance of highly automated vehicles

Remotely operating vehicles utilize the benefits of vehicle automation when fully automated driving is not yet possible. A human operator ensures safety and availability from afar and supports the vehicle automation when its capabilities are exceeded. The remote operator, conceptualized as remote assistant, fulfills the legal requirements in Germany as a Technical Supervisor to operate highly automated vehicles at Society of Automotive Engineers 4. To integrate the remote operator into the automated driving system, a novel user-centered human–machine interface (HMI) for a remote assistant’s workplace was developed and initially evaluated. The insights gained in this process were incorporated into the design of a workplace prototype for remote assistance. This prototype was tested in the study reported here by 34 participants meeting the professional background criteria for the role of Technical Supervisor according to the German law. Typical scenarios that may occur in highly automated driving and require remote assistance were created in a simulation environment. Even under elevated cognitive load induced by simultaneously engaging in a secondary task, participants were able to obtain sufficient situation awareness and quickly resolve the scenarios. The HMI also yielded favorable usability and acceptance ratings. The results of this study inform the iterative workplace development and further research on the remote assistance of highly automated vehicles.

Irreversibility and spectral analysis for nanofluid with melting and higher order slip effects

This work is intended to examine the impacts of first and second-order velocity slips, viscous dissipation, and melting on mixed convective flow of nickel zinc ferrite + SAE 20W-40 motor oil based nanofluid along a stretching or shrinking sheet for the first time. The multigrade 20W-40 motor oil is categorized by Society of Automotive Engineers (SAE). An irreversibility analysis has also been performed using the second law of thermodynamics. The resulting non-dimensional flow-governing equations are modified into ODEs (Ordinary Differential Equations) and then the numerical estimates are provided by adopting the spectral local linearization method. Next, the efficiency of the above-mentioned spectral procedure is verified through the maximum error norms. Finally, the influence of important parameters included in this evaluation on the flow profiles and physical quantities is systematically represented. Based on the findings, the melting effect enhances the heat transference rate by 24.6% and reduces entropy by 38.4%. The use of higher-order velocity slips and viscous dissipation effects results in a lower friction factor. In the presence and absence of ferrite particles, the streamline visualization is clarified. This type of simulation is extremely useful for the readers in considering the rates of cooling or heating at electromagnetic interfaces, industrial devices, orthopedic joint replacements, aircraft turbines, bone plate surgeries, and so on.

Automatic Electric Vehicle Charging Station

Our Automatic Electric Vehicle Charging station is a autonomous power supply unit which works without the need for human attendants. The system is designed to facilitate the existing power grid infrastructure. The system employs the Raspberry Pi as our primary controller board and hosts the User Interface on the LCD Display mounted on the Charger Housing. The Pi Board interfaces with our custom Pilot PCB to communicate with the Electric Vehicle Battery Management Systems to negotiate the charging speed, capacity of the car battery and perform safety checks. The user can choose AC level 1, 2 or DC level 3 charging. The system uses a 30A relay circuit to isolate the battery from the power supply until all the necessary checks and payment processes are completed. RazorPay is our real time Payment gateway for payment transactions. Once the user has completed the formalities the charging process will begin. We also have a charging monitoring system developed that will help users track the battery charge percentage and charging time remaining on the LCD display. The station has emergency Kill Switches and Emergency Stop buttons mounted on the housing to address safety concerns that arise on the advert of damaged high power output utilities, when engaged the entire system will kill all the power inputs from the grid so that any fault can be safely repaired without risk of electrocution. For our implementation and testing we have built a 18650 NMC chemistry 3S5P Battery pack with a 3S BMS. The unit utilizes level 3 AC charging SAE (Society of Automotive Engineering) standards to ensure the safety and quality of the service.

Analysis and improvements of a front wing for formula SAE car

Although aerodynamic packages have been developed for many years, teams still face the problem of lack of downforce and how to control the turbulence. One possible reason is that the size of a formula SAE(Society of Automotive Engineers) car is strictly limited. It is unrealistic to blindly copy Formula 1's aerodynamic package without improving. Aided by CFD (computational fluid dynamics), this article focuses on the front wings aerodynamic characteristics in order to modify the downforce and the flow field around it. The front wing is divided into two parts, one is to direct the airflow bypass the tires, and the other is to diminish the airflow lifted by the front wing. Moreover, a special flap is designed to control the airflow and achieve good results. This article also shows the airflow around the whole car with aerodynamic packages to make the results more vivid. This article may offer a reference for the front wing design of race cars.

A human factors perspective on how to keep SAE Level 3 conditional automated driving safe

The Society of Automotive Engineers (SAE) defines Conditional Automated Driving (CAD) or SAE level 3 as the next step in the transition to higher automated driving. A human factors challenge at this level is to keep the fallback-ready user aware of the driving situation. The problem with the widely accepted terminology of SAE is that it does not consider the human factors of achieving this safety-critical transition and lacks in defining a required or appropriate state of fallback readiness and how a human reaches this state.This paper aims to understand how research and industry currently perceive the problem and how they counteract it. We conducted exploratory expert interviews with N = 15 subject matter experts from universities, research centres and vehicle manufacturers.Based on the findings of the expert interviews, we discuss how fallback-ready users might be kept in the loop. The results show that the user should remain physically and sensory in the state of regular drivers to allow a safe transition, which narrows down the problem to maintaining an appropriate cognitive state, level of arousal, and motivational conditions. Lastly, the experts identify that the NDRA should be (a) limited to the onboard-entertainment system and (b) context-aware and (temporarily) restricted or interrupted. We provide concrete design recommendations grounded in (or drawing upon) theoretical frameworks and current human factors expert views and highlight specific challenges that require more research.

ANALYSIS OF THE EFFECT OF CURRENT AND COOLING MEDIA IN TUNGSTEN INERT GAS (TIG) WELDING ON MECHANICAL STRENGTH AND MICRO STRUCTURE OF AISI 1045 STEEL FOR TRUSS FRAME MOTORCYCLE FRAME CONNECTIONS

AbstractCurrently, metal joining techniques in the field of welding have developed rapidly. In constructions that use metal raw materials, most of the joints are made by welding. Apart from joining, the welding process can also be used for repairs, for example to fill holes in castings, make coatings on tools, thicken worn parts and other repairs. Welding is also widely used for building construction, bridges, piping and automotive. As we know, there are many types of welding used today. One of them is Gas Tungsten Arc Welding (GTAW) or commonly called Tungsten Inert Gas (TIG).AISI 1045 steel is referred to as carbon steel because it complies with international coding, namely the 10xx series based on the nomenclature issued by AISI and SAE (Society of Automotive Engineers). The first number 10 is the code that indicates plain carbon, then the code xxx after the number 10 indicates the carbon composition. So AISI 1045 steel means carbon steel or plain carbon steel which has a carbon composition of 0.45%. Steel of this specification is widely used as a component of gears, shafts and bearings. According to its function, it must be able to withstand wear and tear due to friction with the chain. Wear resistance is defined as resistance to abrasion or resistance to dimension reduction due to friction

Performance Analysis of Relative GPS Positioning for Low-Cost Receiver-Equipped Agricultural Rovers.

Global navigation satellite systems (GNSSs) became an integral part of all aspects of our lives, whether for positioning, navigation, or timing services. These systems are central to a range of applications including road, aviation, maritime, and location-based services, agriculture, and surveying. The Global Positioning System (GPS) Standard Position Service (SPS) provides position accuracy up to 10 m. However, some modern-day applications, such as precision agriculture (PA), smart farms, and Agriculture 4.0, have demanded navigation technologies able to provide more accurate positioning at a low cost, especially for vehicle guidance and variable rate technology purposes. The Society of Automotive Engineers (SAE), for instance, through its standard J2945 defines a maximum of 1.5 m of horizontal positioning error at 68% probability (1σ), aiming at terrestrial vehicle-to-vehicle (V2V) applications. GPS position accuracy may be improved by addressing the common-mode errors contained in its observables, and relative GNSS (RGNSS) is a well-known technique for overcoming this issue. This paper builds upon previous research conducted by the authors and investigates the sensitivity of the position estimation accuracy of low-cost receiver-equipped agricultural rovers as a function of two degradation factors that RGNSS is susceptible to: communication failures and baseline distances between GPS receivers. The extended Kalman filter (EKF) approach is used for position estimation, based on which we show that it is possible to achieve 1.5 m horizontal accuracy at 68% probability (1σ) for communication failures up to 3000 s and baseline separation of around 1500 km. Experimental data from the Brazilian Network for Continuous Monitoring of GNSS (RBMC) and a moving agricultural rover equipped with a low-cost GPS receiver are used to validate the analysis.

Deep reinforcement learning‐based dual‐mode congestion control for cellular V2X environments

AbstractThe Society of Automotive Engineers (SAE) J2945/1 standard for Dedicated Short Range Communication (DSRC) environmentutilizes transmit (Tx) power control and rate control elements for the periodic BSM transmissions, which are intended to work in a complementary manner. An equivalent standard for the cellular vehicle‐to‐everything (C‐V2X) communication environment is J3161/1, but it eliminates Tx power control and uses only rate control. However, the consequence is the degraded update delay of neighbouring vehicles’ kinematics, potentially undermineing driving safety. In this Letter, the authors propose to retain the dual‐mode control in the C‐V2X environment and find a policy through reinforcement learning (RL) to adjust the rate control function to maintain synergy. Moreover, the authors can extract the RL‐created policy from the neural network so that it can be explicitly specified in the standard, and downloaded and used more conveniently by vehicles. Finally, the RL‐generated policy achieves a better packet delivery frequency than J2945/1 or J3161/1.

Application of Arc Thermal Spray Process in Corrosion Protection of Steels and Electromagnetic Pulse Shielding

In the present work, an overview has been discussed on the application of arc thermal spray technology. This process used in erosion, corrosion and electromagnetic pulse (EMP) shielding. The Al coating exhibits excellent corrosion properties in simulated weathering i.e., Society of Automotive Engineers (SAE) J2334 as well as 3.5 wt.% NaCl solution at long run of application. However, weathering condition possesses Cl- and CO3-- ions, which simultaneously influence in the deterioration of Al coating. Once the Zn is alloyed with Al in coating, it enhances the corrosion attributed to the formation of severe defects and galvanic coupling between Al and Zn. The stainless steel and Ti coatings have been used on the concrete surface to reduce the corrosion of waste water reservoir where Ti is exhibited more corrosion resistance due to dense and uniform morphology as well as on the surface of Ti coating during exposure in acidic solution, it forms rutile and anatase, which further provide corrosion protection. Moreover, the Zn has beneficial properties in regards of EMP shielding rather than iron and Cu plate. Zn with copper has excellent EMP shielding compared to pure Cu. As the thickness is increased, the EMP shielding properties are increased. From this review article, it is suggested to reduce the porosity of arc thermal sprayed coating using some chemical post treatment.

L3 Vehicles are becoming a Reality: Important Human Factors Consideration for the Viability of Conditional Automation

As of early 2023, only a limited number of Society of Automotive Engineers (SAE) Level 3 (L3) automated driving systems are available on the market, and they are primarily offered by luxury vehicle brands. SAE L3 automated driving systems are classified as conditional automation (CA), meaning that the vehicle can undertake some well-defined driving tasks under specific conditions, but the driver must be ready to assume control of the vehicle when prompted by the system. It is anticipated that an increasing number of L3 CA systems will be introduced on public roads in the next few years. However, L3 systems pose unique Human Factors (HF) challenges that require thoughtful consideration to ensure that production systems are feasible without compromising driver or road safety. This panel discussion brings together HF researchers and practitioners with expertise in human behavior and usability design for automotive applications to discuss and delineate key issues specifically related to L3 systems, as well as potential approaches to tackle these issues.

Numerical Simulation of Aerodynamic Characteristics of Electric Vehicles with Battery Packs Mounted on Chassis

Aerodynamic characteristics are of great significance to the fuel economy and handling the stability of electric vehicles. The battery pack of electric vehicles has a huge structure and is usually arranged in the chassis area of the vehicle, which inevitably occupies the space at the bottom of the vehicle and affects the aerodynamic characteristics of the vehicle. To study the effect of the power battery pack installed in the chassis on the aerodynamics characteristics of the electric vehicle, the Computational Fluid Dynamics (CFD) method is used to study the flow and pressure fields of the SAE (Society of Automotive Engineers) hierarchical car model with battery packs mounted on chassis. The influence of the structure parameters of the battery pack on the automobile’s aerodynamics are also analyzed in detail. Based on the simulation results, it can be seen that the battery pack installed on the chassis has a great impact on the flow and pressure field at the bottom and tail of the vehicle, causing the drag coefficient and lift coefficient to increase. The structural parameters of the battery pack have contradictory effects on the drag and lift coefficients. As the length of the battery pack increases, the drag coefficient decreases, and the lift coefficient increases. As the battery pack width and height increase, the drag coefficient increases, and the lift coefficient decreases. The research results provide a reference for the optimization of the aerodynamic characteristics of electric vehicles with battery packs mounted on chassis.

Performance analysis of rectangular and double-D transmitters with various receivers for electric vehicle static charging

The inductive charging stations of the future should be able to charge any car, regardless of the type of coil configuration attached to it. In this study the performance of different configurations of coils is investigated. Where the principle of interoperability is studied between the most common types of coils in the IPT system (rectangular and double-D) recommended by Society of Automotive Engineering (SAE) J2954. This interoperability analysis is done at a power level of 11.1 kVA and Z3-class ground clearance using the two types of coils on the side of the car, while double D (DD) is used as a general transmitter in one case, and in the other case, a rectangle (R) is used as a general transmitter. Four 3D finite-element models (FEMs), along with compensation circuits, are built to perform the interoperability tests. The circuit models are utilized to determine the frequency of operation and the parameters of compensation circuit that realize the rated power at highest efficiency. The concept of interoperability has been verified through multiple performance indicators, namely coupling coefficient, transmitted power, and transmission efficiency. These indicators were calculated at ideal alignment and the different cases of misalignment, whether lateral or angular. The findings prove that the two different types of receivers (R and DD) can work efficiently and smoothly with the general transmitter, whether DD pad or rectangular pad are used. At the same time, the nominal power can be transmitted at high efficiency, above the limits permitted by SAE j2954 (>85 % at alignment conditions and >80 % at misalignment conditions).

Misalignment tolerance improvement and high efficiency design for wireless power transfer system based on DDQ‐DD coil

SummaryThis paper addresses misalignment tolerance improvement and high‐efficiency maintenance for wireless power transmission systems. Firstly, a receiving coil is designed according to Standard J2954, published by the Society of Automotive Engineers. Next, a DDQ transmitting coil is designed to accommodate a constrained operating space. The structure and parameters of the transmitting coils are determined to obtain a high coupling coefficient when offset occurs. Subsequently, an analysis is carried out to determine the relationship between the coupler magnetic fields and power transmission ability. A current phase control strategy is developed to deal with the mismatched magnetic fields, and a switching threshold is selected to obtain high power transmission efficiency. Finally, an experimental system is set up using the designed coil. The experimental results demonstrate that the system can maintain high efficiency even when lateral misalignment occurs in different directions. A maximum transmission efficiency of 89.63% is obtained, which validates the effectiveness of the proposed method.

A Taxonomy for Autonomous Vehicles Considering Ambient Road Infrastructure

To standardize definitions and guide the design, regulation, and policy related to automated transportation, the Society of Automotive Engineers (SAE) has established a taxonomy consisting of six levels of vehicle automation. The SAE taxonomy defines each level based on the capabilities of the automated system. It does not fully consider the infrastructure support required for each level. This can be considered a critical gap in the practice because the existing taxonomy does not account for the fact that the operational design domain (ODD) of any system must describe the specific conditions, including infrastructure, under which the system can function. In this paper, we argue that the ambient road infrastructure plays a critical role in characterizing the capabilities of autonomous vehicles (AVs) including mapping, perception, and motion planning, and therefore, the current taxonomy needs enhancement. To throw more light and stimulate discussion on this issue, this paper reviews, analyzes, and proposes a supplement to the existing SAE levels of automation from a road infrastructure perspective, considering the infrastructure support required for automated driving at each level of automation. Specifically, we focus on Level 4 because it is expected to be the most likely level of automation that will be deployed soon. Through an analysis of driving scenarios and state-of-the-art infrastructure technologies, we propose five sub-levels for Level 4 automated driving systems: Level 4-A (Dedicated Guideway Level), Level 4-B (Expressway Level), Level 4-C (Well-Structured Road Level), Level 4-D (Limited-Structured road Level), and Level 4-E (Disorganized Area Level). These sublevels reflect a progression from highly structured environments with robust infrastructure support to less structured environments with limited or no infrastructure support. The proposed supplement to the SAE taxonomy is expected to benefit both potential AV consumers and manufacturers through defining clear expectations of AV performance in different environments and infrastructure settings. In addition, transportation agencies may gain insights from this research towards their planning regarding future infrastructure improvements needed to support the emerging era of driving automation.