In recent years, the development of automotive intelligent driving technology has been rapid. Many advanced driving features have shifted from high-end vehicle configurations to mass-market models, with even models priced over 100,000 yuan equipped with ADAS features. The widespread application of new technologies is a good thing for consumers, but during the car-buying process, these various ADAS functions can confuse many people. What do these English abbreviations mean, and what are their uses?
What Is ADAS? What Functions Does It Include?
ADAS, short for Advanced Driver Assistance System, is an advanced driving assistance system. This name may seem a bit strange, because from the consumer’s perspective, the truly advanced technology would be a car that can drive itself, rather than just “assisting”; the term “advanced” could be seen as self-promotion. So just how advanced is it?
According to the latest 2018 version of the SAE J3016 standard, the driving levels defined correspond to levels L0 to L2. Yes, you read that right; from L0 to L2, all driving functions can be referred to as ADAS, corresponding to the term “Assist”. It is merely an assisting function, which to some extent replaces your eyes, hands, and feet, but the driver is still responsible for driving.In terms of specific functional performance, the examples given in SAE J3016 are quite clear: L0 provides alerts and transient assistance, L1 offers lateral or longitudinal control assistance, and L2 provides simultaneous lateral and longitudinal control assistance.
The Mystery Behind ADAS Function Naming
As seen above, ADAS has many functions and uses numerous abbreviations. When I first encountered these terms at work, I was also confused by these names. After some research, I understood the naming rules for these functions: look at the last letter.W = warning, which indicates warning functions, like BSW (Blind Spot Warning), LDW (Lane Departure Warning), and FCW (Forward Collision Warning);A = assist, indicating assistance functions that have certain execution capabilities, such as LKA (Lane Keeping Assist), TJA (Traffic Jam Assist), and HWA (Highway Assist);P = Pilot, which indicates a combination of multiple ADAS functions, offering stronger capabilities and broader applicability than Assist. For example, Audi’s claimed but not yet realized L3 level Traffic Jam Pilot (TJP) and Highway Pilot (HWP). However, Pilot is also a term that has been misused; originally, TJP and HWP are considered L3 level intelligent driving, but features like Tesla’s AutoPilot, Nio’s Nio Pilot, SAIC’s AI Pilot, and BYD’s DiPilot are all L2 intelligent driving functions that also use the name Pilot.
Overview of Main ADAS Functions
In essence, ADAS assists or replaces the driver in observing, accelerating/braking, and steering operations. Therefore, functions can be divided into lateral functions, longitudinal functions, and combination functions, with the level of assistance capabilities generally increasing from warning → transient execution → assistive execution.Lateral ADAS FunctionsLateral functions refer to ADAS functions related to lateral control of the vehicle, i.e., steering.
Warning function: Lane Departure Warning (LDW)
Assistive execution function: Lane Keeping Assist (LKA)
Longitudinal ADAS FunctionsLongitudinal functions refer to ADAS functions related to longitudinal control of the vehicle, i.e., acceleration and deceleration.
Assistive execution function: Adaptive Cruise Control (ACC)
Combination ADAS Functions
ACC + LKA = Traffic Jam Assist (TJA) or Highway Assist (HWA) (depending on the applicable range)
How to Understand a Car’s ADAS Level
When purchasing a car, pay attention to ADAS. First, check the corresponding configurations. Due to the novelty of the features, the introduction of ADAS configurations is not very user-friendly. Taking the popular automotive website Autohome as an example:Most ADAS features are categorized under active/passive safety equipment options, while adaptive cruise control is listed under assist/control configuration options. So does having these configurations mean that the ADAS levels of these vehicles are the same?Clearly not; just as different manufacturers’ engines and transmissions perform differently, ADAS functions also exhibit different performances. However, the difficulty of evaluating ADAS functions is much higher than that of traditional performance evaluations. For example, evaluating AEB requires multiple tests to determine whether collisions can be avoided at different speeds and with various targets. Evaluating LKA requires testing the ability to maintain lane keeping under different lighting conditions and curvature radii, which imposes new requirements for testing sites and lighting environments. Therefore, testing ADAS functions is far more complex than traditional evaluations of acceleration, braking performance, and collision behavior. Currently, there are no universally recognized comprehensive evaluation metrics and methods for vehicle promotional materials.However, the market is gradually realizing the importance of ADAS evaluations. NCAP has included some ADAS functions in its testing processes, and there are car review media like Garage 42 that have begun to conduct corresponding evaluations of autonomous driving. The following image shows the ADAS capability scoring by Garage 42, known as 42Mark.So how can we understand the ADAS level of vehicles that have not undergone relevant testing? From the logic of ADAS implementation, it is a process of perception → decision-making → execution. Perception is the prerequisite for correct decision-making and execution. As an intelligent driving developer, I suggest starting with the ADAS hardware configuration. Especially for some basic ADAS functions, they generally use vendor solutions, making it relatively easy to compare pros and cons.Cameras and radars are currently the most widely used ADAS sensors. We usually use V (video) and R (Radar) to represent cameras and millimeter-wave radars, with numbers indicating the quantity of each. For example, 1R1V refers to an ADAS system consisting of one radar and one camera. Common configurations include 1V, 1R, 1R1V, 3R1V, 5R1V, and 5R multi-V. More sensors increase costs but definitely improve the accuracy and false alarm rates. Therefore, it can be initially concluded that ADAS systems with more sensors will perform better.In terms of camera solutions, Mobileye‘s camera chips are superior to others, with Mobileye Q4 > Mobileye Q3, and multi-camera systems outperform single-camera systems.From the perspective of sensing solutions, it is necessary to elaborate a bit more: for longitudinal functions like ACC and AEB, there are solutions using millimeter-wave radars, front-view camera radars, and fusion solutions combining cameras and radars. It should be noted that millimeter-wave radars are not very effective at recognizing non-metallic and static objects; AEB functions based solely on millimeter-wave radar may perform poorly on pedestrians and at low speeds. Not understanding this characteristic of radar may pose corresponding risks. On the other hand, camera solutions have less accuracy in distance judgment, which may lead to a poorer functional experience. The fusion solutions can leverage the strengths of both, providing relatively better performance.Another way to understand the ADAS level is from the perspective of functional experience. Moving from 0 to 1 solves the issue of presence, while moving from 1 to 100 requires looking at actual experiential levels, where some quantifiable metrics can be established. Below, I list some common ADAS experience metrics:ACC vs. Full-Speed ACC: Many ACC functions require a speed of over 30 km/h to operate, while full-speed ACC typically works at speeds ranging from 0-150 km/h.LKA’s adaptability to curve radius: The LKA function requires a curve radius of at least 250m, whereas better perception solutions and steering system capabilities can allow the LKA function to adapt to smaller curve radii.Stopping and starting time for TJA function: The TJA function allows the vehicle to automatically follow and stop behind the vehicle in front, which can be very relieving during traffic jams. Short-term congestion or even when the vehicle in front stops can be handled without driver intervention. However, if the vehicle in front stops for a long time before moving again, the TJA function will require the driver to apply some throttle to start. The longer the time the vehicle can remain stopped without requiring driver input, the better the experience.Short-term hands-off time on the steering wheel: Using the TJA function as an example, it allows the driver to take their hands off the steering wheel for a short time, while long-term hands-off will prompt the system to warn the driver to take control. The longer the time allowed for hands-off, the better the driving experience. PS: Traffic regulations require that both hands must not be off the steering wheel simultaneously, but technological advancements may eventually overcome this limitation.Overall, the perspective of driving experience is aimed at minimizing driver intervention and control. These takeover reminders, adaptability to road curvature, etc., cannot be achieved through simple calibration or settings. There is a significant amount of development, simulation, and testing validation work behind to ensure the feasibility of the functions. A better driving experience means more accurate perception, more scientific decision-making, and more precise execution.
Disclaimer: This article is reproduced from Zhihu author @WindyWing, with some images sourced from the internet, for learning and communication purposes only. Please contact for removal if there is any infringement.
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