Road surfaces
How does road surface
affect traffic?
Friction slows down moving things. We need friction to stop, to grip things andto change direction. You need friction to walk. Look at the soles of your shoes! If they're smooth, you'll find they move quite easily over the floor.
If you have grooves on the soles of your shoes, your shoes will grip the ground more.
This is why trainers have deep grooves so you can run, jump and turn without slipping over!
Just like with your shoes on the floor, objects move more easily over some surfaces than others.