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    Speed assistance not working properly

    Your car shows a speed limit that isn't correct, warns about a limit that doesn't apply there, or, when linked to cruise control, unexpectedly adjusts its speed. This is often described as a problem with speed assistance.

    Intelligent Speed Assistance (ISA) helps the driver stay within the applicable speed limit. Among other things, the system uses traffic sign recognition and digital speed data. Since July 2024, ISA has been mandatory on new cars in the European Union.

    An incorrectly recognised speed doesn't automatically mean the system is faulty. How it behaves depends on what the vehicle detects and which information it uses.

    Have you experienced an unexpected speed adjustment or an incorrect speed display? Report your experience to ADAS Meldpunt. Your report helps show where speed assistance reacts differently in practice than expected.

    Does this sound familiar? Share your experience with ADAS Meldpunt. Your report helps build a clearer picture of how driver assistance systems perform in everyday driving.

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    What does Intelligent Speed Assistance do?

    Speed assistance informs or supports the driver about the applicable speed limit. Depending on the vehicle, the system may warn when you're driving too fast, show the recognised speed limit on the dashboard, or actively influence the speed.

    The system determines the speed limit from a combination of information. Which sources a vehicle uses varies by make and model.

    • traffic sign recognition via a camera;
    • digital speed data from map information;
    • in some vehicles: a link to Adaptive Cruise Control (ACC), so the set speed is automatically adjusted.

    What unexpected behaviour might you experience?

    The points below describe experiences, not diagnoses.

    • the displayed speed limit doesn't match the actual situation;
    • a road sign is misread, for example a sign on a parallel road or slip road;
    • when linked to cruise control, the car unexpectedly lowers or raises the set speed;
    • the car brakes unexpectedly after a lower speed limit has been recognised;
    • the warning stays active after the speed zone has already been passed;
    • temporary signage at roadworks is not recognised, or recognised incorrectly.

    Why might speed assistance react differently than expected?

    An unexpected speed adjustment can have several causes. A single event isn't enough to establish which factor was the cause; that requires an examination of the vehicle and the situation.

    • incorrect recognition of a road sign, for example near slip roads, parallel roads or temporary signage;
    • incorrect or outdated digital speed data in map information;
    • how the vehicle links speed recognition to cruise control;
    • conditions that can affect the camera, such as glare, rain or dirt;
    • the road layout or unusual signage;
    • a technical fault or an issue with sensor calibration.

    What can you do about a speed assistance problem?

    The driver remains responsible for the driving task and the speed being driven. Once the situation has passed and you can do so safely, note down the following details:

    • location and direction of travel;
    • date and time;
    • which speed limit the car displayed;
    • which speed limit you believe actually applied;
    • whether cruise control was switched on;
    • exactly what the car did;
    • any signage at the location, for example near roadworks;
    • whether the same behaviour has happened before.

    Reporting and getting it checked

    Check your car's handbook to see how speed assistance works in your vehicle and which sources of information the system uses. If the behaviour occurs regularly, have a qualified garage or service centre check whether a software update, inspection or calibration is needed.

    Report a speed assistance problem → In the report form, you can select "Speed recognition / ISA combined with ACC" under driver assistance system if the speed adjustment happened via cruise control. A report does not replace a technical diagnosis.

    Can I turn off speed assistance?

    The controls vary by vehicle. For systems covered by the relevant European requirements, the driver must be able to override the system. Where switching off is possible, the system returns to its normal operating mode each time the vehicle is started.

    If unexpected behaviour happens repeatedly, simply switching it off doesn't explain the cause. Have it checked if necessary to find out why the system is reacting this way.

    Frequently asked questions

    Traffic sign recognition uses a camera and can be affected by the position of the sign, signage on parallel roads or slip roads, temporary signs at roadworks, and conditions such as glare or dirt. Some vehicles also use digital map data, which can be out of date. A single event isn't enough to establish the cause.

    In some vehicles, the recognised speed limit can be linked to Adaptive Cruise Control (ACC). The car can then automatically adjust the set speed. If a road sign is misread or the speed data is incorrect, this can make the car slow down unexpectedly.

    Yes. Since July 2024, new cars in the European Union must be fitted with Intelligent Speed Assistance (ISA). The driver must still be able to override the system.

    Note down where and when it happens and which speed the car displayed. Check your handbook to see which sources of information the system uses, and ask a qualified garage or service centre to check it if the behaviour occurs regularly. You can also report your experience to ADAS Meldpunt.

    Yes. You can report without giving your name or email address. A registration number is required, though, to link the report to the correct vehicle type. Your registration number is not stored in readable form; it is pseudonymised.

    An independent reporting platform

    ADAS Meldpunt is an independent initiative. It is not affiliated with any vehicle manufacturer, importer, insurer, regulator or other government body.

    We do not sell cars or carry out repairs, and we receive no payment from manufacturers, importers or insurers for the content of reports.

    Reports are used to understand how driver assistance systems work and how they can be used safely, and to identify possible patterns of unexpected or unwanted behaviour. Personal data is kept protected.

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