In recent years, some vehicle manufacturers have begun to offer "driver control assistance systems (DCAS)" on their vehicles. Different vehicle manufacturers use different names to describe these systems, but essentially they assist the driver by regulating the acceleration and deceleration of the vehicle in accordance with traffic flow whilst ensuring that the vehicle follows the road/lane contour. However, although such systems provide support for the driver, reducing the driver’s workload and increasing comfort, they do not completely take over the driving task and the driver must remain in control of the vehicle, monitoring the environment around the vehicle and the vehicle’s/system’s performance. For these reasons, such systems are classified as SAE Level 2.
Due to the fact that there were no United Nations Economic Commission for Europe (UN ECE) Regulations covering such driver control assistance systems (DCAS), in 2021, the UN ECE Working Party on Automated/Autonomous and Connected Vehicles (GRVA) set up a specific Task Force to develop a new UN ECE Regulation on DCAS which would specify uniform provisions and safety requirements for such systems that were technology neutral. The final result of this Task Force’s work is UN ECE Regulation No. 171, which came into force on September 22, 2024.
This new Regulation is applicable to Driver Control Assistance Systems (DCAS) fitted to M and N category vehicles, i.e. passenger cars, multipurpose passenger vehicles, vans, pick up trucks, heavy trucks, buses and coaches. Within the Regulation, DCAS are defined as "the hardware and software collectively capable of assisting a driver in controlling the longitudinal and lateral motion of the vehicle on a sustained basis".
The Regulation specifies numerous design and performance criteria that the DCAS must comply with and specifies test procedures to which a DCAS equipped vehicle must be subjected to demonstrate compliance with those requirements. In addition, the Regulation specifies that the vehicle manufacturer must compile documentation detailing the design and operation of the DCAS, the safety concept for the DCAS and evidence to demonstrate that thorough consideration of functional and operational safety has been applied throughout the design and development of the system. This documentation must be submitted to the Technical Service at the time of type approval for them to review. The Technical Service may also request that a DCAS equipped vehicle is subjected to additional testing, beyond the test procedures specified in the Regulation itself, to confirm the safe operation of the system.
The design and performance requirements specified in the Regulation include requirements covering the following:
- Response to system boundaries - Specifying how the system must react when any operating condition exceeds the boundaries within which the systems is designed to operate, e.g. transitioning control back to the driver.
- Controllability - Specifying that, in all conditions, the vehicle must remain controllable by the driver, whether the driver is intentionally overriding the system or when control is being transitioned back to the driver.
- Lane positioning - Specifying that that system must assist in keeping the vehicle in a stable position within its lane of travel, whilst following the road / lane contour.
- Undertaking “manoeuvres” - Specifying that, where systems are capable of undertaking manoeuvres, such as lane changes, turns at road intersections, negotiating roundabouts, etc., the system must undertake such manoeuvres in a safe manner without endangering other road users.
- Driver state monitoring - Specifying that the vehicle must be equipped with a system which constantly monitors the driver to ensure that the driver is observing the road ahead and is available to take over the driving task, if necessary, i.e. eyes on the road and hands on the steering wheel.
- Driver disengagement warning - Specifying the optical, audible and haptic warnings and warning escalation sequence that must be implemented by the system if the driver is determined to be disengaged.
- Risk mitigation function - Specifying that the vehicle must be capable of safely bringing the vehicle to a halt where the driver has been determined to be unavailable.
- Speed limit compliance - Specifying that the system must automatically control the vehicle speed. The system must also determine the applicable speed limit for the road on which the vehicle is travelling and provide warnings to the driver if the speed limit is being exceeded.
- System response to detected failures - Specifying how the system must react when a failure is detected within the system or one of its components, e.g. providing warnings to the driver and transitioning control back to the driver in a safe manner.
- System activation and deactivation - Specifying the conditions which must be met for the system to be activated and the conditions which must cause automatic deactivation of the system, with a suitable transition back to driver control.
- Driver information - Specifying the optical, audible and haptic signals and messages that must be provided to the driver to signify operational status of the system and to provide any necessary warnings.
- Driver information materials - Specifying the information that must be included in the vehicle’s user manual regarding the system, including information on the system’s capabilities and the driver’s responsibilities when the system is in operation.
- Software updates - Specifying that the procedures and processes for any software updates must comply with the requirements of UN ECE Regulation No. 156.00 on software updates.