Vehicles equipped with automatic emergency braking traveling at 35 MPH collided with a stopped vehicle 33% of the time when they were tested during simulated rainfall. Lane keeping assistance did even worse with test vehicles departing their lane a staggering 69% of the time.

AAA conducted the “rainfall” testing and released the findings of the research in late October. Typically, advanced driver assistance systems (ADAS) are assessed in ideal operating conditions versus settings that mimic real-world bad weather conditions.

Essentially, the AAA evaluations found that moderate to heavy rain impacts on a safety system’s ability to “see,” which can result in performance issues.

For example, even when traveling at just 25 MPH, vehicles with automatic emergency braking resulted in a collision for 17% of the test runs.

Today’s advanced safety systems rely on sensors and cameras to see road markings, other cars, pedestrians, and obstacles, so it should come as no surprise that rain might obscure the technology’s visibility.

Noteworthy, AAA also tested the vehicles with a simulated dirty windshield —covered with a concentration of bugs, dirt, and water — and found that overall performance was not negatively impacted.

Even so, AAA notes that ADAS cameras can be influenced by a dirty windshield. It is important drivers keep their windshields clean for their own visibility and to ensure their ADAS system camera is not obstructed.