Why are highways actually tilted?

Why are highways actually tilted?

Next time you are driving on a perfectly straight highway, look closely. It is not actually flat. If it were, rain would just pool on the surface, turning the road into a dangerous water slide.

Instead, engineers build a hidden slope into the road called a Normal Crown. The center is slightly raised, dropping off exactly two percent toward the edges. It is steep enough to instantly shed water, but gentle enough that you never feel it.

Every time you take a sharp corner, a phantom force is actively trying to throw your car off the road. This is centrifugal force. Your tires fight back with friction, but at high highway speeds, friction alone simply isn't enough.