Why does banking a curve on a highway allow a vehicle to go faster around it?

Question

Why does banking a curve on a highway allow a vehicle to go faster around it?

Answer 1

It allows the normal force of the road pushing on the car to provide some of the centripetal force rather than relying on friction to provide all the force.

Draw yourself a couple of force diagrams.  One should be for a car turning on a level road.  You've got gravity down, the normal force up, and friction in providing all the centripetal force.  The other should be a car turning on a banked road.  Gravity is still down, but now the normal force has an inward component that will help out the friction.

Answer 2

Because the tilt of the car compensates for some of the outward force (centripetal) due to the curve, and makes it less likely you will lose traction.

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Answer 3

Banking the curve raises the angle so that the road can provide normal force towards the centre of rotation. The road is then capable of providing frictional force and normal force to contribute towards the centripetal force required for the acceleration needed to round the corner.

This allows a faster speed because more force is provided,

F(centripetal) = mv^2/r so F is proportional to v^2 hence larger speed is achieved through more force provided by road.

Horizontal road cannot provide the normal force, only frictional .