Currently camera (player character's head) reacts to accelerations caused by the car's movement, but it isn't pronounced enough. This is especially visible, when driving offroad and hitting a major bump at speed.

From personal experience, driving offroad car shakes you terribly all over the cabin, even with seatbelts fastened and racing seat installed. Adding such shake would make driving more immersive, as well as it would provide additional visual cues about what the car is doing and how far it can be pushed, before something unpleasant happens.