If the car is on an arch bridge, the centripetal force is downward. The centripetal force is the resultant force of the car. Because gravity is also downward, the direction of the supporting force of the bridge to the car is uncertain, depending on specific problems.

If the car is on the concave bridge, the centripetal force is upward. Because gravity is downward, the supporting force of the bridge to the car must be upward and greater than gravity.

I hope to help you again. You can ask.