In Bad Weather, Advanced Vehicles May Not “See” the Road

During new AAA testing, lane-keeping, automatic braking features struggled with rain

BOISE – Advanced driver assistance systems, or ADAS, have the potential to significantly reduce the number of fatal and injury crashes on American roads.  But AAA warns that when rain and other inclement weather are in the forecast, these systems may not operate as intended.

Car manufacturers often test safety features like automatic emergency braking and lane keeping assistance in ideal weather conditions in order to replicate the results and rule out other variables.  But during AAA’s new research, test vehicles traveled on a closed course under a simulated downpour of moderate to heavy rainfall.

The results were shocking.  Test vehicles traveling at 35 mph collided with a stopped “dummy” vehicle in the lane ahead of them about a third of the time.  And lane keeping assistance was even less effective, with test vehicles departing their lane 69% of the time in rainy conditions.

“During times of rain, snow, ice and fog, all of which are common in Idaho, drivers who own vehicles equipped with these features should stay alert and be ready to take over at a moment’s notice,” says AAA Idaho spokesman Matthew Conde.  “Someday, this advanced technology may be able to do everything on its own, but for now, there’s no substitute for an engaged driver.”

ADAS rely on a combination of sensors and cameras to “see” the road and take appropriate action.  But just like foggy lenses on a pair of glasses, reduced visibility can cause the vehicle to misjudge the situation, including its relative position on the road and distance from other cars.

In another test, AAA researchers evaluated the systems’ performance with a dirty windshield.  While the vehicles were largely unaffected by grime, AAA notes that keeping a windshield clean is just as important to drivers as it is to the machines that support them.

To simulate steady rainfall, AAA engineers designed a system with a reservoir and precision nozzle that sprayed the windshield at a predictable rate.  The dirty windshield was created by using a custom-made stamping tool to apply a mixture of bugs and dirt.

Safely using ADAS

AAA offers these tips to keep you safe behind the wheel in bad weather:

  • Don’t rely too much on the tech. These systems are intended to provide “assistance,” not replace your role as an attentive driver.
  • Know how it works. Use your vehicle owners’ manual to better understand how these features are intended to work, and under what conditions.
  • Keep it clean. Keep areas around cameras and radar sensors clean and free of dirt and grime.  The owner’s manual will provide the location of sensors and recommend proper cleaning procedures.  Make sure windshield wipers are working well, too.
  • Increase your following distance to 5-6 seconds and reduce speed in bad weather.
  • Stay calm. If your car starts to hydroplane, ease off the accelerator to gradually reduce speed until your tires regain traction, and continue to look and steer in the direction you want to go.  Don’t slam on the brakes – this could make the problem worse.

“Our hope is that auto manufacturers will expand their testing to include the real-life scenarios that Idahoans face every day, including when the weather gets a little rough,” Conde said.  “A better understanding of system limitations will inspire further innovation and ultimately lead to a system that is so reliable that it can be completely trusted.”