Full context:   If the gap is less than G, the driver tends to adapt his speed to the speed of the preceding vehicle without caring what the precise gap is, so long as this gap is not smaller than the safe space gap g safe (labelled by speed adaptation in Figure 5). Thus the space gap g in car following in the framework of Kerner's three-phase theory can be any space gap within the space gap range g safe ≤ g ≤ G .