set INTER;  
set ROADS within (INTER cross INTER);

param cost {ROADS}; 
param limit {ROADS}; 
param b {INTER};  

node Intersection {i in INTER}: net_out = b[i];

minimize TotalFlowCost;

arc Traff {(i,j) in ROADS} >= 0, <= limit[i,j], from Intersection[i], to Intersection[j], obj TotalFlowCost cost[i,j];