AAA:  Heavy Rain Affects Vehicle Safety Systems

More and more drivers are relying on driver assistance technology these days. But just how effective is it when it comes to driving in inclement weather, like say rain? That's the question AAA set out to answer in recent testing. Researchers tested systems using simulated rainfall and concluded that moderate to heavy rain impedes a vehicle safety system’s ability to “see”, which it says may result in performance issues.

Here's how the testing worked. AAA says it simulated rainfall in a closed course setting. By that AAA means its engineers designed a water system with a high-pressure pump and a precision injector nozzle to spray the windshield. This system was placed in the cargo area of the test vehicle and was connected to a nozzle positioned above the windshield so that the spray pattern covered the entire windshield. (AAA notes that water sprayed by this system did not reach the pavement or interact with the test vehicle’s tires.)

Next AAA tested how systems like automatic emergency braking (AEB) and lane keeping assist worked under those conditions.  AAA says test vehicles equipped with AEB  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.

AAA says it believes real-world driving situations like this must be incorporated into testing procedures.

“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.”

Simulated Rain

AAA conducted its test 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

AAA researchers also say some systems may provide an alert or deactivate in extreme situations, however, the conditions AAA tested under provided no such alert or warning.

Simulated Dirty Windshield

Unlike the test results involving the simulated rain, only minor differences in performance were noted when testing with a simulated dirty windshield (stamped with a concentration of bugs, dirt and water). AAA says in those tests, performance was not negatively impacted. However, AAA says advanced driver assistance system cameras can still be influenced by a dirty windshield so they recommend drivers keep their windshields clean for their own visibility and to ensure their ADAS system camera is not obstructed.  AAA also recommends keeping windshield wipers clean so they aren't streaking the windshield and causing issues for ADAS cameras.

AAA Testing

This is the latest AAA test evaluating ADAS systems. AAA says its previous testing of vehicle safety systems in both closed-course and real-world settings shows that performance is greatly impacted by driving scenarios, road conditions and vehicle design. It notes system shortcomings like:

• Struggling to stay within in a marked lane in moderate traffic, on curved roadways and on streets with busy intersections
• Failing to stop for pedestrians in common scenarios like crossing in front of a vehicle, a child darting out between two parked vehicles, or walking at night
• Colliding with a simulated disabled vehicle and instances of coming too close to other vehicles or guardrails

AAA says safety systems vary widely and are not a replacement for a fully engaged driver. 

“AAA recognizes these systems have the ability to lessen the chance of a crash and improve the overall safety of driving,” continued Brannon. “Fine-tuning their performance and providing drivers with a more consistent experience will go a long way in unlocking their true potential.”

AAA also says it's important for drivers to understand how their vehicle's driver assistance technology works by reading their owner’s manual.  Check out our online owner manual guide here .

Driving Tips

Regardless of whether your vehicle is equipped with safety technology, wet conditions pose a challenge for motorists. AAA recommends using extra caution in slick conditions by doing the following:

• Keep windshield clean and ensure that wipers are not streaking the windshield.
• Slow down and avoid hard braking and sharp turning. If possible, follow in the tracks of other vehicles.
• Increase following distance to 5-6 seconds behind the vehicle ahead.
• Do not use cruise control in order to stay alert and to respond quickly if the car’s tires lose traction with the road.
• If the car begins to hydroplane, ease off the accelerator to gradually decrease speed until the tires regain traction, and continue to look and steer where you want to go. Don’t jam on the brakes—this can cause further traction loss.

You can check out more rainy weather driving tips here.

Photo Credit:  AAA