Automatic emergency braking system upgraded to mandatory standard! Review of AEBS regulations in various countries

This mandatory standard is revised based on the recommended standard GB/T39901-2021 "Performance Requirements and Test Methods for Automatic Emergency Braking Systems (AEBS) for Passenger Cars" (see the end of the article for the complete PDF file of the recommended standard). After the revision, there are mainly the following changes.

Firstly, the scope of application of the standard has been expanded to include N1 vehicles, and the system’s ability to identify and respond to vulnerable traffic participants such as pedestrians and two-wheeled vehicles has been increased; in addition, the system’s performance robustness has been increased and the assessment of system errors has been enriched.

Secondly, in terms of main technical content, the standard specifies the performance requirements and test methods for the automatic emergency braking system of light vehicles, mainly including the self-check, status prompt, warning signal, braking deceleration, false response, functional safety, etc. of the automatic emergency braking system, and provides corresponding test methods.

Finally, compared with the mandatory international AEBS regulations such as ECE R152, this mandatory standard is more consistent with international standards in terms of technical requirements and examines the performance of the system from more dimensions.

In addition, it is worth noting that in May this year, the Ministry of Transport issued four amendments to the Standard No. 1 (draft for comments) for the management of operating vehicles, directly requiring that operating buses, trucks, tractors and dangerous goods road transport operating vehicles must be equipped with automatic emergency braking systems (AEBS) and meet relevant technical requirements.

Automobile Development

So, how important is AEBS that national management departments have continuously issued standard policies?

Why is AEBS so important?

According to the data of the World Health Organization, about 1.35 million people die in traffic accidents and millions are injured every year. More than 80% of these traffic accidents are caused by the negligence and slow reaction of drivers.

Mercedes-Benz and Eaton in the United States have studied various types of traffic accidents and found that if drivers can recognize the danger of collision 1-2 seconds in advance and take collision avoidance measures, most traffic accidents can be avoided. Thus, the Advanced Emergency Braking System (AEBS) was developed.

AEBS is an active safety technology that uses automatic braking to avoid or mitigate collisions. It belongs to the category of advanced driver assistance system (ADAS). Among many ADAS systems, AEBS has attracted much attention due to its important role in improving driving safety and reducing traffic accidents.

The AEBS system detects and identifies the vehicle ahead through cameras or radars, and uses sound and warning lights to remind the driver to brake to avoid a collision if a collision is possible. If the driver still does not brake, the system determines that a rear-end collision is unavoidable, and will automatically brake to mitigate or avoid the collision.

The technology also includes Dynamic Brake Support, which supplements the driver's braking force when the force applied to the brake pedal is not enough to avoid an imminent collision.

According to the difference in road conditions, AEBS can be divided into urban AEBS for urban road conditions, inter-city AEBS for highway conditions, and pedestrian AEBS for protecting pedestrians.

Urban AEBS mainly uses lidar to detect target vehicles within 10 m ahead and works when the vehicle speed does not exceed 20 km/h; intercity AEBS mainly uses long-range radars such as millimeter-wave radar to detect target vehicles within 100 m ahead and works when the vehicle speed is between 50 and 80 km/h; pedestrian AEBS mainly uses cameras, infrared devices, etc. to detect target pedestrians.

Common AEBS collision avoidance strategies

①Safe distance collision avoidance strategy based on driving distance

It refers to the safe distance that should be maintained to avoid collision with the vehicle in front as much as possible. The real-time distance between the vehicle and the vehicle in front is used as an indicator to measure the dangerous driving state from the distance scale, and compared with the warning safety distance and emergency braking safety distance in the strategy, so as to guide the AEBS system to make warning and active braking collision avoidance operations.

In the strategy, the warning safety distance and the emergency braking safety distance are mainly determined in real time by parameters such as the vehicle speed, the relative speed with the target vehicle, the maximum braking deceleration of the vehicle, the maximum braking deceleration of the target vehicle, the system delay time, the driver's reaction time, and the distance between vehicles that need to be maintained after the vehicle stops.

As early as the end of the 20th century, Mazda, Honda and the U.S. Highway Safety Administration proposed classic safety distance collision avoidance strategies such as Mazda, Honda and NHTSA in order to develop the AEBS system as soon as possible.

②Collision avoidance strategy based on the driver's reaction characteristics

It refers to the time to collision (TTC) from the current motion state of the vehicle to the collision with the vehicle in front, which is used as an indicator to measure the driving danger state, under the condition that the driver's cognition and judgment of the driving danger situation are met.

The strategy divides the actual vehicle distance obtained by the front radar by the relative vehicle speed to obtain the real-time TTC value, and compares it with the TTC value of the collision warning and the TTC value of the emergency braking set in the system, thereby guiding the AEB system to make warnings and active braking to avoid collisions. Domestic and foreign automobile manufacturers and universities have carried out a lot of theoretical and practical research on collision avoidance strategies at the time of collision, and applied them to the AEB system collision avoidance strategy.

③ Braking and steering coordinated collision avoidance strategy

It refers to the coordinated work of the longitudinal AEBS and the lateral active steering system to achieve complete collision avoidance of the target ahead. It is mainly used to deal with the situation where the AEBS system cannot achieve complete collision avoidance of the target ahead at high speeds and low vehicle distances through pure longitudinal braking.

For example, if a pedestrian suddenly crosses the road in front of the vehicle, the real-time TTC changes instantly and is less than the emergency braking TTC. At this time, even if AEBS is fully effective, the vehicle will still collide with the pedestrian at a higher speed. In the collaborative collision avoidance strategy, the AEBS system still needs to provide support for active braking and active steering process braking control during the entire collision avoidance phase, which places higher requirements on the system's collision avoidance strategy.

Existing AEBS-related regulations or standards

In order to systematically test and evaluate the performance of AEBS and make the system suitable for various driving environments, various countries and regions have successively formulated regulations or standards related to AEBS technology, such as the long-standing UN R152 in the European Union, the current GB∕T 39323 in my country, and the newly released FMVSS 127 regulations in the United States...

UN R152 "Uniform Provisions for Type Approval of Advanced Emergency Braking Systems (AEBS) for Type M1 and N1 Motor Vehicles" is the United Nations' requirements for the certification of AEBS systems for M1 and N1 vehicles. Only when these requirements are met can they enter the EU market through United Nations certification.

Talking about car finishing

Table 1: Vehicle-to-vehicle scenarios

The left side shows the maximum relative collision speed of the M1 vehicle (km/h)

The right side shows the maximum relative collision speed of the N1 vehicle (km/h)

Table 2: Vehicle-to-Person Scenario

The left side shows the maximum collision speed of M1 vehicles (km/h)

The maximum collision speed of N1 vehicle (km/h)

Table 3: Vehicle-to-cyclist scenarios

The left side shows the maximum collision speed of M1 vehicles (km/h)

The right side shows the maximum collision speed of N1 vehicle (km/h)

GB∕T 39323 "Performance Requirements and Test Methods for Passenger Car Lane Keeping Assist (LKA) System" is a promotion standard that came into effect in October 2021. The standard stipulates several aspects including early warning and warning signals, performance requirements, warning signals after system failure, driver intervention performance, and false response performance.

Talking about car finishing

FMVSS 127 Automatic emergency braking systems for light vehicles: On May 9 this year, it was officially released by the National Highway Traffic Safety Administration (NHTSA) of the United States, and stipulated that from September 1, 2029, newly produced light vehicles must meet the requirements of FMVSS 127.