Autonomous vehicles need to be cleaned more often than regular cars but putting them through an automated car wash could actually cause other hazardous issues, according to a CNN report.

Autonomous vehicles have dozens of sensors and in order to keep them free of obstructions, the exterior of a self-driving vehicle needs to be cleaned frequently. Anything that sticks on the exterior such as twigs, leaves, bird droppings, or dead insects can get in the way of cameras and radar, and interfere with the vehicle's ability to drive safely.

Yet there are reasons why autonomous vehicles should not be subjected to the traditional automated car wash. For starters, soap residue or water spots could effectively blind an autonomous car. Moreover, the heavy brushes used in car washes can be particularly hazardous to self-driving cars. For example, brushes could jar the vehicle's sensors, disrupting their calibration and accuracy. Worse still, brushes could actually break the sensors, causing a significant safety risk, reports CNN.

So just how are manufacturers keeping self-driving vehicles clean and safe? The old-fashioned way, reports CNN. Toyota, Aptiv, Drive.AI, and Uber perform manual cleanings using microfiber cloths along with rubbing alcohol, water, or glass cleaner.

In frigid conditions, Uber has a worker apply windshield washer fluid with a squirt bottle to its camera lenses. A puff of air is then used to remove whatever residue remains. Toyota primarily uses rubbing alcohol on a cloth to clean camera lenses, but sometimes relies on cleaning wipes. Self-driving startup May Mobility uses just a cloth and water for the entire vehicle.

Some manufacturers such as Cruise and Seeva are building sensor cleaning equipment into their autonomous vehicles, which may alleviate some of the need for manual cleaning, reports CNN. However, experts say that due to the sheer number of sensors, manufacturers need to find a better, long-term solution.