Autonomous Vehicle, a little deep dive about Level 3
There are words that we often come across when we hear news or advertisements about autonomous driving (AD). That’s ‘Level’. Of course, there are many cases where the term ‘Autonomous Driving’ is simply explained at once. However, the scope of the definition of technology is rather wide to be simply expressed as autonomous driving. In order to clarify this ambiguous part, it is the classification for driving automation introduced by SAE that is cited a lot.
The recent mentioned level in this classification would be probably ‘Level 3’. Some media is expressing this as an autonomous driving level where you can put your hands off the steering wheel from Level 3 (L3). Well, that could be not a wrong statement. However, it is also true that there are not many introductions to the constraints hidden behind L3 features. But already, automakers are unveiling the introduction of L3 cars to the market.
In this article, I would like to talk a little deep to help you understand Level 3, which is an intermediate level in the implementation of fully autonomous driving technology. Since the term Level 3 originated from SAE J3016, I will focus on the J3016. In addition, I would like to introduce the contents of other fields related to Level 3. Some technical terms appear, but I’ll try to keep it as simple as possible.
Contents
1. Classification of Driving Automation in SAE J3016
2. Level 3, terminology for understanding
3. Level 3, a little deep story
4. Level 3, UN regulation, ALKS
5. Level 3, ready of companies
1. Classification of Driving Automation in SAE J3016
SAE J3016, which is currently being introduced as a classification standard for driving automation, was first introduced in 2014 to reduce confusion with the advent of driving automation technology. Afterwards, through three revision updates in 2016, 2018, and 2021, the current version 202104 is the final version.
SAE J3016 divides the automation level of driving into 6 stages. These are Level 0~2, which is the Driver Support level, and Level 3~5, which is the Automated Driving level. Many of the driving automation features that are selling today are Level 2 or lower included in driver assistance. In other words, the expression ‘autonomous driving’ must not be used in the automation technology of automobiles currently on sale. Of course, because each company has a function that exceeds Level 2, expressions such as Level 2+ and Level 2++ are sometimes used. However, J3016 does not allow expressions other than Level 2.
Of course, the classification of SAE cannot be said to be absolute, but since it is a widely used classification method, understanding of each level is necessary at least. Before diving into Level 3’s in-depth discussion, I would like to briefly introduce the SAE’s driving automation classification.
>> Driver Support <<
Level 0: No Driving Automation
Level 1: Driver Assistance
Level 2: Partial Driving Automation
>> Automated Driving <<
Level 3: Conditional Driving Automation
Level 4: High Driving Automation
Level 5: Full Driving Automation
2. Level 3, terminology for understanding
SAE J3016 is the document titled “Taxonomy and Definitions for Terms Related to Driving Automation Systems for On-Road Motor Vehicles”. It can be seen that J3016 aims to reduce confusion for users by clearing up the terminology for driving automation. Initially, J3016 was created for developers, not for the public. Since then, as it has been introduced to the public, SAE has also given various methods to help them understand it.
Since this article is meant to be a little in-depth about Level 3, I summarize some technical terms to help you understand in advance.
※ I briefly introduce some terms for reference purposes below. Since this is a brief summary, please refer to J3016 for more details.
▶ Automated Driving System (ADS) — The hardware and software that are collectively capable of performing the entire DDT on a sustained basis, regardless of whether it is limited to a specific operational design domain (ODD); this term is used specifically to describe a Level 3, 4, or 5 driving automation system. (3.2)
▶ Dynamic Driving Task (DDT) — All of the real-time operational and tactical functions required to operate a vehicle in on-road traffic, excluding the strategic functions such as trip scheduling and selection of destinations and waypoints, and including, without limitation, the following subtasks (3.10)
- Lateral vehicle motion control via steering (operational).
2. Longitudinal vehicle motion control via acceleration and deceleration (operational).
3. Monitoring the driving environment via object and event detection, recognition, classification, and response preparation (operational and tactical).
4. Object and event response execution (operational and tactical).
5. Maneuver planning (tactical).
6. Enhancing conspicuity via lighting, sounding the horn, signaling, gesturing, etc. (tactical).
▶ [DDT] Fallback — A vehicle function (not an ADS function) designed to automatically bring an ADS-equipped vehicle to a controlled stop in path following either: (1) prolonged failure of the fallback-ready user of a Level 3 ADS feature to perform the fallback after the ADS has issued a request to intervene, or (2) occurrence of a system failure or external event so catastrophic that it incapacitates the ADS, which can no longer perform vehicle motion control in order to perform the fallback and achieve a minimal risk condition. (3.12)
▶ Minimal Risk Condition (MRC) — A stable, stopped condition to which a user or an ADS may bring a vehicle after performing the DDT fallback in order to reduce the risk of a crash when a given trip cannot or should not be continued. (3.16)
▶ [DDT Performance-Relevant] System Failure — A malfunction in a driving automation system and/or other vehicle system that prevents the driving automation system from reliably performing its portion of the DDT on a sustained basis, including the complete DDT, that it would otherwise perform. (3.17)
▶ Object and Event Detection and Response (OEDR) — The subtasks of the DDT that include monitoring the driving environment (detecting, recognizing, and classifying objects and events and preparing to respond as needed) and executing an appropriate response to such objects and events (i.e., as needed to complete the DDT and/or DDT fallback). (3.19)
▶ Operational Design Domain (ODD) — Operating conditions under which a given driving automation system or feature thereof is specifically designed to function, including, but not limited to, environmental, geographical, and time-of-day restrictions, and/or the requisite presence or absence of certain traffic or roadway characteristics. (3.21)
▶ Request to Intervene — An alert provided by a Level 3 ADS to a fallback-ready user indicating that s/he should promptly perform the DDT fallback, which may entail resuming manual operation of the vehicle (i.e., becoming a driver again), or achieving a minimal risk condition if the vehicle is not operable. (3.25)
▶ Usage Specification — A particular level of driving automation within a particular ODD. (3.30)
▶ [DDT] Fallback-Ready User — The user of a vehicle equipped with an engaged Level 3 ADS feature who is properly qualified and able to operate the vehicle and is receptive to ADS-issued requests to intervene and to evident DDT performance-relevant system failures in the vehicle compelling him or her to perform the DDT fallback. (3.31.3)
PS: if you need more vocabulary related to autonomous driving, please visit here.
3. Level 3, a little deep dive story
The core of Level 3 can be said to be an intermediate level between the driver assistance and the fully autonomous driving. In other words, it can be thought of as being in the middle of the boundary between human and robot driving control. For this reason, the description of Level 3 is longer than the others. In short, it’s a complicated.
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J3016 is basically classified based on the following when dividing the level of driving automation.
a. Whether the driving automation system performs either the longitudinal or the lateral vehicle motion control subtask of the DDT.
b. Whether the driving automation system performs both the longitudinal and the lateral vehicle motion control subtasks of the DDT simultaneously.
c. Whether the driving automation system also performs the OEDR subtask of the DDT.
d. Whether the driving automation system also performs DDT fallback.
e. Whether the driving automation system is limited by an ODD.
The table below defines Level 3 based on the above criteria.
For classification of driving automation, it is important who has driving control. In Level 3, the roles of users and ADS are as follows.
Here are some cases where DDT Fallback occurs while ADS is in the process of automated driving.
As introduced earlier, between ADS and User, it is dividing the driving automation by defining roles in DDT and DDT fallback. And the function of each level allows manufacturing companies that implement the function to define and use the operational characteristics including the requirements and ODD of each level. And J3016 introduces low-speed, stop-and-go highways as an example of Level 3 ADS application.
4. Level 3, UN regulation, ALKS
Among automobile makers, Honda in March 2021 was granted permission for Level 3 function and disclosed that it sells cars. In the case of Honda, it was permitted to operate only in Japan. And in December 2021, Mercedes-Benz announced that it had received the world’s first international approval for Level 3 operation. So, what kind of permission did Mercedes-Benz get to sell cars equipped with Level 3 functions that can be operated internationally? It has passed the R157 regulatory test published by UNECE. This is a regulation called ‘Automated Lane Keeping Systems, ALKS’. ALKS is a regulation that will be released in June 2020 and will be approved by 54 countries from January 2021. It is disclosed by UNECE at a time when an international consensus on autonomous driving technology is needed along with the technological advancement of automobile automation. If J3016 is the definition of driving automation, ALKS contains the contents of various conditions necessary for driving automobiles.
First of all, ALKS is defined as “for low speed application is a system which is activated by the driver and which keeps the vehicle within its lane for travelling speed of 60 km/h or less by controlling the lateral and longitudinal movements of the vehicle for extended periods without the need for further driver input”.
In addition, it defines the criteria necessary to engage ALKS and is mandatory a driver monitoring system can respond to the driver’s DDT fallback and a data storage system (Data Storage System for Automated Driving, DSSAD) that records the situation after ADS is activated. It must also comply with regulations on cybersecurity and software updates released with ALKS.
And since companies that sell vehicles equipped with the ALKS function must satisfy the performance standard requirements in countries adopting this regulation to sell them, the regulations also include test-related contents. For reference, standards such as ISO, SAE, and KS do not have compulsory powers, but regulations have a compulsory effect, so it can be said to have a great influence on companies. Of course, based on the ALKS published by UNECE, each country can put its own additional requirements. For example, a separate effort is being made to increase the speed set at 60 km/h to over 100 km/h.
Recently, UNECE announced an amendment to apply ALKS, which was applied only to passenger cars (M1), to trucks and long-distance buses. In this article, I have only given a brief introduction to ALKS. For more details, please refer to the original ALKS document. You can check the details of implementation of Level 3 features.
5. Level 3, ready of companies
Previously, I explained the terminology and current international regulation with a little deeper contents about Level 3. So, let’s see what the situation is for automakers that actually need to implement these features.
The automation technology for automobiles currently on sale is Advanced Driver Assistance Systems(ADAS) technology, which can be said to be a Level 2 or lower. In other words, in a car with a human driver, it is an assistive function that the driver needs. However, automakers cannot wait for the blurry expectations of fully autonomous vehicles. It can be said that it is a situation where we have to overcome the technical limitations through Level 3.
Currently, some companies have already obtained Level 3 related permission and released their technology, such as Honda and Mercedes-Benz, while others are introducing functions under obscure names such as Level 2+ in ADAS technology. For reference, it is revealed that the number of Level in J3016 does not specify or imply hierarchy in terms of relative merit, technology sophistication, or order of deployment. In a word, Level 4 doesn’t mean “better” than Level 3. It explains that this distinction can reduce the clarity of the roles of users and ADS. (J3016 / 8.3)
In any case, automobile manufacturers are using unique names for automobile automation technology, and in brief, they are as follows.
Companies that are released or planning to Level 3
- Honda — Traffic Jam Pilot
- Mercedes-Benz — Drive Pilot
- Hyundai — Highway Driving Pilot (to be released in the second half of 2022)
- Volvo — Ride Pilot (to be unveiled at CES 2022)
- BMW (to be released in 2022)
- Stellantis (to be released in 2024)
ADAS function, but a company preparing for Level 3 or higher
- GM — Super Cruise, Ultra Cruise
- Ford — BlueCrusie
- Nissan — ProPILOT 2.0
- Tesla — Autopilot, FSD (Beta)
It is usually called autonomous driving from Level 3. Well, it’s not completely wrong. However, the expression ‘fully autonomous driving’ cannot be used. As mentioned earlier, Level 3 has some conditions to use the term fully autonomous driving. The most important thing is that not only robots but also person is involved in driving. This is the important point.
We now need to know the obvious limitations of the upcoming Level 3 features and avoid their misuse. And the introduction of these limitations and the development of technology for functional constraints must be carried out by automobile manufacturing companies first. Currently, this is one of the difficulties in developing the technology. Of course, there is not only technical, but also social and legal. And because the wrong marketing strategies of the company can lead users to the wrong use, the introduction and education of the function is important also.
I would like to emphasize once again.
Level 3 must be activated in a situation where person is ready to drive in a dedicated area at any time.
Over the Vehicle !!!
