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    Adaptive Cruise Control not working properly

    Your car brakes unexpectedly even though the road ahead is clear, accelerates when you're not expecting it, or adjusts the set speed on its own. This is often described as a problem with Adaptive Cruise Control.

    Adaptive Cruise Control (ACC) automatically keeps a distance from the vehicle ahead and adjusts the car's speed accordingly. In some vehicles, ACC is linked to speed recognition (ISA), so the set speed can also be adjusted to the recognised speed limit.

    An unexpected adjustment 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 braking or speed adjustment? Report your experience to ADAS Meldpunt. Your report helps show where Adaptive Cruise Control 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.

    Report an incident

    What does Adaptive Cruise Control do?

    ACC maintains the set speed and automatically adjusts it when the system detects a slower vehicle ahead of you. It usually uses a radar for this, sometimes combined with a camera.

    In a growing number of vehicles, ACC can be linked to Intelligent Speed Assistance (ISA). The car can then automatically adjust the set speed to the recognised or digitally received speed limit.

    What unexpected behaviour might you experience?

    The points below describe experiences, not diagnoses.

    • the car brakes unexpectedly even though there's no vehicle ahead of you;
    • the car reacts to a vehicle in a neighbouring lane or in a bend;
    • the car accelerates unexpectedly, for example after the vehicle ahead changes lane;
    • the set speed is automatically adjusted after a road sign is recognised;
    • the car slows unexpectedly near a slip road or parallel road;
    • the system switches itself off or is temporarily unavailable.

    Why might ACC react differently than expected?

    An unexpected braking or 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.

    • detection of a vehicle or object that the system judges to be relevant, for example in a bend;
    • incorrect recognition of a road sign, or outdated digital speed data, when linked to ISA;
    • the shape of the road, such as bends, gradients or slip roads;
    • conditions that can affect the sensors, such as rain, snow or dirt;
    • the road layout or temporary traffic arrangements;
    • a technical fault or an issue with sensor calibration.

    What can you do about an ACC problem?

    The driver remains responsible for the driving task and must be able to intervene when the vehicle reacts differently than expected. Once the situation has passed and you can do so safely, note down the following details:

    • location and direction of travel;
    • date and time;
    • the set speed and exactly what the car did;
    • whether speed recognition was linked to cruise control;
    • the traffic situation, for example a bend, slip road or vehicle ahead;
    • any signage at the location;
    • weather and visibility conditions;
    • whether the same behaviour has happened before.

    Reporting and getting it checked

    Check your car's handbook to see how ACC works in your vehicle and whether it's linked to speed recognition. Keep the sensor areas clean according to the manufacturer's instructions.

    If the behaviour occurs regularly, have a qualified garage or service centre check whether a software update, inspection or calibration is needed.

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

    Frequently asked questions

    ACC adjusts speed based on what the sensors detect. In bends or near slip roads, the system can judge a vehicle or object to be relevant. Linked speed recognition can also cause the car to slow down when a road sign is misread. A single event isn't enough to establish the cause.

    In some vehicles, the recognised or digitally received speed limit can be linked to cruise control. The car can then automatically adjust the set speed. If the speed data is incorrect, this can make the car slow down or speed up unexpectedly.

    Adaptive Cruise Control (ACC) automatically keeps a distance from the vehicle ahead. Intelligent Speed Assistance (ISA) informs or supports the driver about the applicable speed limit. In some vehicles, the systems are linked.

    When the system repeatedly brakes or accelerates unexpectedly, shows a fault warning, or after damage or a repair involving sensors. A qualified garage or service centre can check whether inspection, calibration or a software update is needed.

    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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