The
degree of saturation (DoS) of an intersection (typically under
traffic signal control) or a link measures the demand relative to the total capacity. A DoS value of 100% meaning that demand and capacity are equal and no further traffic is able to progress through the junction. The formula to calculate DoS is: • Degree of saturation = (demand x cycle time) / (saturation flow x effective green time) Values over 85%-90% typically indicate
traffic congestion, with queues of vehicles beginning to form. The
practical reserve capacity (PRC) refers to the available spare capacity at a junction. ==Ratio of Flow to Capacity==