Advanced vehicle systems: ISA to be introduced


After a transitional period of two years, it will be mandatory to equip new vehicles with intelligent speed assistance (ISA) in the European Union from 7 July 2024. From that date, the registration of a vehicle without such a system will be prohibited (see under D8 in Annex II of Regulation 2019/2144).

Background and legislative basis

The reason for introducing the ISA is the objective pursued by Regulation 2019/2144 of further improving road safety through the mandatory introduction of advanced vehicle systems. The intelligent speed assistance system described in Article 6(2) of Regulation 2019/2144 is such an advanced vehicle system within the meaning of the regulation.

The specific operation and technical requirements of the ISA are described in more detail in Delegated Regulation 2021/1958 and its annexes. Where reference is made below to specific points, these refer to the provisions in Annex I of Delegated Regulation 2021/1958.

Design of the ISA and how it works

The Speed Limit Information Function (SLIF) is an integral part of the ISA system in accordance with point 2.1. Corresponding information systems have been in use for some time in the automotive sector, such as the display of the maximum speed limit recognised by the vehicle on the dashboard or head-up display.

The further configuration of the ISA is variable. For one thing, the SLIF can be combined with a Speed Limit Warning Function (SLWF). As the name suggests, this feature actively warns the driver as clearly as possible if the maximum permitted speed is exceeded. According to point 3.5.2, this warning can be given in various forms; for example, visually and acoustically in a cascade or only haptically via the accelerator pedal. Alternatively, the ISA can also be equipped with a speed control feature (SCF), which intervenes and automatically reduces the speed if the speed limit is exceeded.

Technical specifications

Regarding vehicles in the field already equipped with ISA, some customers have found the system to be annoying, as acoustic warnings are given even when the speed limit is marginally exceeded and the assistance system cannot be permanently disabled. However, the manufacturers cannot be “blamed” for this technical design, as they are bound by technical specifications in this respect. In detail:

  • The ISA must issue a warning (or, depending on the system configuration, automatically reduce the speed) if the speed limit recognised by the system is exceeded even slightly. According to point 3.2.3, a maximum speed tolerance of 3.0% is permitted. This means, for example, a tolerance of only 1.5 km/h at a speed of 50 km/h.
  • According to point 3.2.1, it must generally be possible to disable the ISA. However, permanent disabling is not permitted. This means that the system is automatically reenabled at the latest once the vehicle has been restarted (see point
  • While some internet forum users report that the ISA is highly error-prone when recognising the maximum permitted speed, this experience is likely to be subjective. According to point 2.2, the ISA must be designed to avoid or at least minimise the error rate under real driving conditions. If high-performance traffic sign recognition is used in combination with GPS data and digital map material, the system should be very reliable (see also recital 14 of Delegated Regulation 2021/1958).

Automatic disabling when controlled by ALKS

Given that vehicle automation is increasing, an interesting aspect is found in point 3.2.2, which states that automatic disabling of the ISA is permitted if the vehicle is controlled by an Automated Lane Keeping System (ALKS). The technical requirements of ALKS are described in more detail in UN Regulation No. 157. This is a level 3 automation system that is sufficiently sophisticated to keep the vehicle in lane on motorways or dual carriageways in compliance with traffic regulations, to detect obstacles and to change lanes without further driver command. Therefore, under certain conditions, the ALKS is able to perform the driving task instead of the driver.

If the vehicle is controlled by ALKS, it makes no sense to warn the driver since the vehicle must recognise and comply with the maximum permitted speed on its own. If (approved) driving features are designed as required according to section 1a(2) of the German Road Traffic Act, drivers in Germany are permitted also under behavioural law (section 1b(1) of the German Road Traffic Act) to turn their attention away from the traffic situation and vehicle control. This means that the driver may rely on the correct functioning of the automatic driving feature and compliance with traffic regulations (within the limits of section 1b(2) no. 2 of the German Road Traffic Act, i.e. obvious malfunctions of the system).

Conclusion and outlook

It remains to be seen whether the mandatory introduction of ISA will meet with broad customer acceptance. Many manufacturers are now moving away from allowing the ISA to be disabled only in a (potentially complex) menu structure in the vehicle settings, and instead are allowing the driver to disable the system also by pressing and holding a button on the steering wheel, for example. Eventually, manufacturers have a certain freedom in how to implement the required features.

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