Which statement describes the difference in road friction between dry and wet conditions?

• A. Friction on a dry surface is the same as a wet surface
• B. Wet surfaces have greater friction than dry
• C. Friction present on a dry surface differs from that on a wet surface
• D. Road surface friction is not affected by moisture

Answer: (C)

Friction at the tire–road interface changes when moisture is present. On a dry surface, the tire rubber digs into the road’s microtexture, creating a strong grip and higher friction. When the road is wet, a thin water layer can act like a lubricant, reducing direct rubber–road contact and lowering the friction coefficient; water can even lift portions of the tire at higher speeds, increasing the risk of hydroplanning. Because moisture alters how the tire interacts with the road, friction on a dry surface differs from friction on a wet surface.