characteristics of the intersection that cause drivers to merge in a defined manner. This merging process can be defined by split priority, p, which is the ratio of μ2* to μ1* (p = μ2* / μ1*). A common split priority rule is the "zipper rule", which describes two flows merging where vehicles merging alternate between the two input streams. Solving the model can be done graphically, where the four possible states of the system are visible on a plot of the two inlet flows, and boundaries defined by the relationships in the model. The feasible region for q1 and q2 is bounded by the relationships that the flow in inlet 1 cannot be greater than μ1 and similarly for inlet 2, and the relationship of q1 + q2 = μ. All solutions must be within this region, bounded in red in the figure. A second boundary is the feasible region for demands, the maximum possible values for q1D and q2D, defined to be μ1 and μ2, and is bounded by black in the figure. The split priority, p, is plotted from the origin to the line q1 + q2 = μ. State A1 is when both inlets are in free flow. All combination of inlet demands in this region (q1D, q2D) produce unchanged inlet flows (q1, q2). State A2 is when inlet 1 is in free flow and inlet 2 is in congestion. Inlet demands in this region produce inlet flows where all of q1D merges while q2 = μ − q2D and a queue builds in inlet 2. State A3 is when inlet 1 is in congestion and inlet 2 is in free flow. Inlet demands in this region produce inlet flows where all of q2D merges while q1 = μ − q1D and a queue builds in inlet 1. State A4 is when both inlets are in congestion. All inlet demands in this region produce inlet flows equal to where the split priority vector intersects the feasible region of q1 and 2, at (μ1*, μ2*). See also Traffic flow References Road traffic management