i started this project in march 2022 and gived up, because the collision didn't work. You could fly through the walls and hills. I stopped this project. And now in autumn i tried it again for the improve jam.
First I removed the transform.position-controls because they destroy the physic-engine of Unity. I made the movement with:
m_Rigidbody.AddForce(car.transform.forward * speed * Time.deltaTime);
To stop the increasing speed i made ---> if(m_Rigidbody.velocity.magnitude > 3000) m_Rigidbody.velocity = m_Rigidbody.velocity.normalized * 3000;
Of course i give the player a rigidbody and a box collider. The course can't have a boxcollider, i take a mesh-collider and select the course as mesh.
But first the player moved down, so I fixed in the Rigidbody 4 constraints.