Monday, 18 October 2021 15:59

Rained Out: Vehicle Safety Systems Struggle to ‘See’ in Bad Weather

Written by Ellen Edmonds, AAA


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New research from AAA finds moderate to heavy rain affects a vehicle safety system’s ability to “see," which may result in performance issues.

During closed course testing, AAA simulated rainfall and found that test vehicles equipped with automatic emergency braking traveling at 35 mph collided with a stopped vehicle one third (33%) of the time. Lane keeping assistance didn’t fare any better, with test vehicles departing their lane 69% of the time.


Vehicle safety systems, also known as advanced driver assistance systems or ADAS, are typically evaluated in ideal operating conditions. However, AAA believes testing standards must incorporate real-world conditions that drivers normally encounter.


“Vehicle safety systems rely on sensors and cameras to see road markings, other cars, pedestrians and roadway obstacles. So naturally, they are more vulnerable to environmental factors like rain,” said Greg Brannon, AAA’s director of automotive engineering and industry relations. “The reality is people aren’t always driving around in perfect, sunny weather so we must expand testing and take into consideration things people actually contend with in their day-to-day driving.”


Research Shows Rain has the Biggest Effect on Vehicle Safety Systems


AAA, in collaboration with the Automobile Club of Southern California’s Automotive Research Center (ARC), simulated rain and other environmental conditions (bugs and dirt) to measure impact on the performance of ADAS like automatic emergency braking and lane keeping assistance.


Generally, both systems struggled with simulated moderate to heavy rain.


Automatic emergency braking engaged while approaching a stopped vehicle in the lane ahead:

  • In aggregate, testing conducted at 25 mph resulted in a collision for 17% of test runs
  • In aggregate, testing conducted at 35 mph resulted in a collision for 33% of test runs


Lane keeping assistance engaged to maintain the vehicle’s lane position:

  • In aggregate, veered outside of the lane markers 69% of the time


During testing with a simulated dirty windshield (stamped with a concentration of bugs, dirt and water), minor differences were noted; however, performance...

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