ADAC Tests Emergency Braking Assist Systems in Rain and Fog
How reliable are emergency braking assist systems under poor visibility conditions? This question was investigated by the ADAC in a recent test. The study examined the behavior of various new vehicles in heavy rain and dense fog – conditions that pose a significant challenge both for drivers and for driver assistance systems. The tests were conducted in a weather hall operated by AVL, where different environmental and visibility conditions could be simulated realistically and reproducibly. Only professional test facilities and high quality ADAS targets from 4activeSystems were used.
Realistic Test Conditions as a Basis
Within the weather hall, scenarios such as heavy rain, dense fog, and changing lighting conditions were deliberately created.
The test vehicles drove at a constant speed of 30 km/h in two standardized scenarios:
A stationary vehicle (4activeC2 RMT – rear vehicle ADAS target with brake lights) and a crossing pedestrian (4activePA adult).
Each test run was repeated several times to ensure comparable and reliable results.
Such tests place high demands not only on vehicle sensor technology and algorithms, but also on the test equipment itself.
Precise motion sequences, stable guidance of target objects, and reliable operation under wet conditions and reduced visibility are essential to enable an objective assessment of driver assistance systems.
Varying System Performance in Adverse Weather Conditions
The test results show that emergency braking assist systems do not always function without limitations in challenging weather conditions. In particular, dense fog caused many vehicles to fail to reliably detect crossing pedestrians or stationary vehicles in all test runs. As a result, collisions in these situations could often only be mitigated, or in some cases not fully avoided at all.
A positive exception was the Mercedes CLA, which demonstrated robust performance even in dense fog and darkness. In addition, the tests made it clear that beyond braking performance itself, how vehicles handle system limitations also plays an important role. Clear indications of restricted sensor capability or reduced system availability can provide valuable support to the driver.
Contribution of 4activeSystems
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