There is a maximum highway capacity formula_17: If the flow rate is close to the maximum capacity formula_17, then even small disturbances in free flow at a bottleneck will lead to a spontaneous F → S phase transition. On the other hand, only very large disturbances in free flow at the bottleneck will lead to a spontaneous F → S phase transition, if the flow rate is close to a minimum capacity formula_16 (see, for example, Sec. 17.2.2 of the book). The probability of a smaller disturbance in free flow is much higher than that of a larger disturbance. Therefore, the higher the flow rate in free flow at a bottleneck, the higher the probability of the spontaneous F → S phase transition. If the flow rate in free flow is lower than the minimum capacity formula_16, there will be no traffic breakdown (no F →S phase transition) at the bottleneck.