Originally Posted by justinsain

It's to simulate the G force you would feel when driving a race car.

Your eyes look straight at the monitor so it's not about you body's orientation
in relation to the ground. Notice when he brakes in a straight line the rig dips down
causing the body to feel like it is pushed forward as one would feel upon braking.

Same principle as a sim ride at Disney only this isn't enclosed and you can see the immediate surroundings.