What is a requirement for passenger cars regarding safety equipment?

Windshield wipers are a crucial safety feature required for passenger cars because they ensure that drivers can maintain clear visibility while driving in inclement weather, such as rain or snow. Proper functioning windshield wipers help to remove water, debris, and other obstructions from the windshield, allowing the driver to see the road and surrounding environment. This visibility is essential for safe driving, helping to prevent accidents caused by impaired sightlines due to weather conditions.

While rearview mirrors are also important for safety, they alone do not provide the comprehensive visibility needed in adverse weather. Air conditioning and navigation systems, while they can enhance comfort and convenience, are not safety requirements for passenger cars and do not directly impact the ability to drive safely.