A viral driving tip claims that every motorist should keep a glass of salt inside the car. Although the story about a police officer may be exaggerated, the basic idea has a practical explanation: salt can attract moisture from the surrounding air.

During cold or rainy weather, damp shoes, wet clothing, breathing, and small leaks can raise the humidity inside a vehicle. When that warm, moist air touches cold windows, condensation forms and the glass becomes foggy. Leaving coarse salt in an open container overnight may absorb a small amount of moisture, potentially reducing condensation by morning.

However, this trick should not replace the car’s proper defogging system. Drivers should use the windshield defroster, air conditioning, and fresh-air setting to clear fog before moving. Wet items should be removed, and persistent moisture may indicate leaking door seals, blocked drains, or another problem that needs attention.

A loose drinking glass is also unsafe because it could spill or become a projectile during sudden braking. Anyone trying the idea should use a stable, sealed breathable container or a purpose-made reusable moisture absorber, positioned securely while the vehicle is parked.

Salt may offer a cheap temporary solution, but it is not magic. Clear visibility, functioning ventilation, and repairing the source of excess moisture remain far more important for safe driving.