“…Whereas in models belonging to the fundamental diagram approach (e.g., [10,12,16,18,22,23,36,39,46,49,47] and the reviews [2, 1]) a vehicle would close up to the leading one adjusting its speed and gap as required by secure driving, in models with the basic structure (1), (3), a driver within the synchronization distance D n adapts his speed to the one of the vehicle in front without caring, what the precise gap is, as long as it is safe. This explains why there is no unique flow-density relationship for steady states in the present CA models.…”