[1] A formula to calculate saturation flows based on lane geometry is given in Transport and Road Research Laboratory RR67.
[3] 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: Values over 85%-90% typically indicate traffic congestion, with queues of vehicles beginning to form.
[4] For priority junctions including roundabouts, the equivalent measure to DoS is the ratio of flow to capacity (RFC).