1. Preface
ADAS (Advanced Driver Assistance Systems) have been developed to support drivers and enhance road safety. Among the products on the market are warning systems to advise of a safety hazard; control systems to improve the ease of control during normal driving and help avoid accidents and/or mitigate the crash severity in critical situations. In June 2011, the WP.29/ITS Informal Group developed and proposed basic guidelines for imminent warning systems, part of which was already referred to in the regulatory discussion of AEBS (Advanced Emergency Braking Systems) and LDWS (Lane Departure Warning Systems).
Studies on control systems are under way in various countries and regions, but they have not yet resulted in internationally uniform guidelines. However, control systems require a certain basic understanding for development, because it is imperative that the average driver is able to safely and comfortably operate these systems according to his/ her intentions and take full control as needed. To address this concern, Europe has conducted studies under the RESPONSE 3 project and Japan similar studies under the ASV project.
This document focuses on control systems among ADAS and summarizes the minimum necessary principles that are of vital importance for HMI (Human-Machine Interaction) in the use of control systems. Considering that newly developed control systems are still on the way and that a variety of systems will be marketed in the future, this document focuses on general principles that are applicable across the board and not those applicable only to specific systems.
In the main text of this document, we first describe the principles that are important for HMI in the use of ADAS. For control systems, there are twelve principles in total. Next, in the form of an annex, we summarize some issues in automation, important viewpoints and future tasks for HMI based on findings and experience. Reference is made to the influence of further automation of these systems that is expected as control systems evolve.
This document was drafted by the IHRA (International Harmonized Research Activities)-ITS working group, revised several times, and then submitted to the ITS Informal Group. The next step is left to the discretion of the ITS Informal Group. It should be noted that this document is not aimed at regulation but was written as a reference for the stakeholders who are engaged in the design and development of human-centered ADAS
2. Scope
ADAS can be classified into three categories: information provision, warning, and control. Guidelines for limiting driver distraction from in-vehicle information systems have already been established and are used on a self-commitment basis. Regarding warnings, the ITS Informal Group submitted the "Guidelines on establishing requirements for high-priority warning signals", which was adopted at the 154th session of WP.29 in June 2011.
This document discusses control systems that support and assist the driver’s driving operations. Systems covered include those that involve a certain interaction (transfer of control) between the driver and the system, but exclude those that control the driving operations independently. Therefore, this document does not discuss existing ABS (Anti-lock Braking Systems) and ESC (Electronic Stability Control), nor does it cover information provision systems such as navigation devices.
In this document, we discuss systems that are used during normal driving, such as ACC (Advanced Cruise Control system) and LKS (Lane Keeping-assistance System), as well as systems used in critical situations, such as AEBS (Advanced Emergency Braking Systems), to avoid accidents and mitigate crash severity. AEBS are currently being regulated, but we include them in our discussion because they involve the transfer of control between the driver and the system.
The present principles are applicable mainly to passenger cars (M1), but the basic philosophy is applicable to other categories of vehicles. Therefore, it is desirable that they are also applied to vehicle categories such as M2, M3, N1, N2, and N3. The principles are expected to apply to both original equipment and aftermarket devices. It should be noted, however, that there may be some difficulties coordinating aftermarket devices with the control systems fitted by vehicle manufacturers.
3. Existing Regulations
There are existing Regulations which are most relevant to the principles in this document.
/ UN Regulation No. 121 Vehicles with regard to the location and identification of hand controls, tell-tales and indicators
/ FMVSS No. 101 Controls and displays.
/ UN Regulation No. 130 Lane Departure Warning System (LDWS)
/ UN Regulation No. 131 Advanced Emergency Braking Systems (AEBS)
4. Control Principles
The principles are divided into four sections:
Control elements;
Operational elements;
Display elements; and
Supplementary elements.
A total of twelve principles are established. Each principle defines the main Recommendations to be fulfilled for the HMI to allow the driver to easily and accurately understand and judge driving situations and effectively use the control system according to their intentions.
The section on control elements and operational elements is divided into those for normal situations and those for critical situations, and an explanation is given on how the control system should be operated. In the section on display elements, the discussion covers the notification of normal functionality, failure, reduction in the scope of functionality, and the transfer of control. The section on supplementary elements includes a warning against over-reliance on sensors and systems, which is potentially dangerous, and discusses the use of standard symbols and information for road users.
In this document, normal driving refers to situations that do not require immediate responses from the driver and/or vehicle to avoid a collision. Critical driving refers to situations that do require immediate responses from the driver and/or vehicle to avoid or mitigate a collision.
4.1. Control Elements
(a) System actions should be easy to override at any time under normal driving situations and when collisions are avoidable.
Explanation: One of the main objectives of ADAS such as ACC, etc., used in normal driving situations, is to reduce the driving workload. During normal driving, the system should be capable of being overridden by the driver using simple, deliberate action(s) at any point in time.
(b) When a collision is determined to be imminent, the system can take actions intended to avoid and/or mitigate the crash severity.
Explanation: In critical driving situations where the driver has not taken proper avoidance actions because of impairment, distraction, inattention, or other unforeseen incidents, it should be possible to apply system intervention to try to avoid the collision or mitigate the crash severity.
4.2. Operational Elements
(a) For systems that control the vehicle under normal driving situations, the driver should have a means to transition from ON to OFF manually and to keep the system in the OFF state.
Explanation: For ease of use and/or convenience in driving, the driver’s intentions should be ensured as a priority, so that the driver can switch the state of control from system to driver that is from ON to OFF and the OFF state should be kept under the driver’s operation.
(b) For systems that control the vehicle under critical driving situations, the initial set state of the system should be ON.
Explanation: For collision avoidance and/or mitigation, the first priority is to reduce trauma, therefore the system status ON should be maintained during driving. However, accounting for driver preferences, the system can be equipped with a manual OFF switch. In this case the system status should be recognizable to the driver
4.3. Display Elements
(a) Drivers should be provided with clear feedback informing them when the system is actively controlling the vehicle’s speed and/ or path.
Explanation: When the system is actively controlling the vehicle, the driver should be provided with clear feedback on its activation. The driver has to be made aware of system activation so as to properly manage driving a car with assistance systems.
(b) Drivers should be informed of the system status when system operation is malfunctioning or when there is a failure.
Explanation: When the system is malfunctioning or has failed, the driver should be informed of the system status. This is needed to avoid any misunderstanding by the driver that the system is still working.
(c) The driver should be informed when the system detects that conditions are such that normal performance cannot be assured.
Explanation: When the system is not fully functioning, for example, the sensor performance is impaired under certain driving conditions such as rain or when road markings are not visible, the driver should be informed of the status to allow a smooth transfer of control to the driver.
(d) Drivers should be notified of any system-initiated transfer of control between the driver and vehicle.
Explanation: Transfer of control between the driver and the vehicle would be the point when automation is realized. Any transfer of control should be transparent to the driver, but at the very least, the driver should be notified of any transfer initiated by the system so the driver is always aware if they have control of the vehicle.
4.4. Supplementary Element
(a) In cases where systems automatically control the longitudinal and lateral behaviour of the vehicle and the driver’s task is to monitor system operations, appropriate arrangements should be considered to prompt the driver to maintain their attention to the vehicle, road and traffic situation.
Explanation: When the driver is using highly automated systems such as ACC with LKS, which is the automation of longitudinal and lateral control, the driving tasks are reduced and the driver simply monitors the systems and surroundings. In these situations, it is important to ensure the driver’s attention to the driving task is maintained. To ensure that the driver stays aware of the driving situation, appropriate measures should be considered to keep the driver in-the-loop.
(b) Drivers should be notified of the proper use of the system prior to general use.
Explanation: The manufacturer should provide information on correct system use to avoid any misunderstanding and/or over-dependence on the system. For example, it is required that the driver understand what assistance systems are installed in the vehicle, and that instructions be provided on the physical limitations of the system functions prior to its use.
(c) If symbols are used to notify the driver, a standard symbol should be used if available.
Explanation: Taking into account the use of different and/or unfamiliar vehicles, commonality of information should be secured, therefore standard symbols should be used, if available. UN Regulation No.121 could be the one that might be referred.
(d) System actions requiring the attention of other road users should be signaled to other road users.
Explanation: To help surrounding road users, such as other drivers, pedestrians, and cyclists, be aware of vehicle actions, the system’s actions should be signaled when braking, changing lanes or for hazards. In consideration of the system functions and driving situation, the need for display might be determined on a case-by-case basis.
5. Summary
ADAS control systems are still being developed and various new systems will emerge in the future. For the development of technologies, it is important to continuously improve the safety and user-friendliness of these systems for the average driver. If a negative effect is felt, these systems may lose credibility among the general public and subsequent development may be hindered. To prevent such an event and to encourage proper development of the systems, it is important to define the principles to be followed as a basic guideline.
These principles are limited to the main Recommendations considered to be of critical importance. However, systems that arrive on the market in the future may require guidance for aspects that are not covered. Changes over time may also make some of the principles obsolete or unnecessary. The present principles shall therefore be revised as appropriate, and this task should be assigned to the ITS Informal Group (in some cases in consultation with the respective GR group that may govern a specific system in question), since the present principles deal with ADAS in general and not with specific systems.
As a future process, the UNECE WP.29 ITS Informal Group and other relevant working groups in the UNECE WP.29 will engage in comprehensive discussions on a mechanism that will ensure effective implementation of the control system principles. This annex was adopted by WP.29 at its 160th session (ECE/TRANS/WP.29/1104, para.22) and transmitted to the Working Party on Road Safety (WP.1) as a reference.
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