Comfort systems pose risks on roads outside built-up areas

Driver assistance systems such as emergency brake assist can significantly increase road safety. However, a distinction must be made between safety systems and comfort systems. While the former make a major contribution to road safety, the latter harbor risks.

Too much trust in systems is dangerous

Comfort systems such as cruise control and lane departure warning (combined) support the driver over a longer period of time. They help to keep the vehicle centered in the lane and brake or accelerate if necessary. The longer the systems provide support, the greater the risk of inattention and distraction. It becomes particularly dangerous if the system suddenly switches off after a long period of activity. Drivers may then no longer be able to intervene appropriately and in good time.

Special challenges on roads outside built-up areas

Compared to freeways - the actual intended area of application for such comfort systems - roads outside built-up areas have tighter bends, poorer road markings, oncoming traffic, junctions and other road users. The study shows that this results in three central challenges for the use of comfort systems:

• Unreliable lane guidance: Vehicles left the lane or were in danger of running into oncoming traffic on straight stretches because the system steered towards the center of the lane due to a lack of lane markings.
• Incorrect speed selection: Both the selection of an appropriate speed and the precise recognition of speed limits proved to be prone to error.
• Inconsistent braking and acceleration processes: without clear points of reference, the system regulated the speed incorrectly, for example after a vehicle in front had turned off or when leaving a traffic circle.

Drivers need to know the functions and limits of assistance systems in order to be safe on the road. You can read all the details in the new study «Assisted driving functions on rural roads». The study is available in German.

Source: AAIB