Road surfaces

How does road surfaces affect friction?

Friction is higher on rough, surfaces, and high friction slows things down more. Roads that have lots of fast traffic have rougher surfaces so cars can grip and stop more easily. When a rough surface gets wet, the water fills the dips and grooves in the road and makes the road smoother. With a wet surface friction is reduced and cars can't stop as quickly. This is why it is even more important to follow the road safety rules in wet weather. Not only may it be harder for the driver to see you, but even if the driver does see you, he or she may not be able to stop in time.

When it is freezing cold, the roads become even more dangerous because ice and snow make a totally smooth road surface so the car's tyres cannot grip. This means vehicles take even longer to stop. You may also have problems walking, so take extra care not to slip over while crossing the road! Click play to view the animation.