The objective function (1) represents the minimization of the maximum working time of all tankers;
Constraint (2) indicates that each gas station is served by at least one tanker;
Constraints (3)-(4) indicate that the start point and the end point of each tanker’s distribution route must be
the oil depot;
Constraint (5) indicates that if a tanker drives into a gas station, it must leave the gas station when the task is
completed;
Constraint (6) indicates that the total amount of the refined oil which is loaded in a tanker is no more than the
capacity of the tanker;
Constraint (7) indicates the relationship of arrival time between two adjacent gas stations on the same distribution
route;
Constraint (8) means that the time for tanker to arrive at a gas station must be in its time window;
Constraint (9) indicates that the amount of the refined oil of all tankers deliver to a certain gas station is equal
to its demand;
Constraint (10) ensures that the time that all tankers return to the oil depot is no longer than the maximum
working time;
Constraints (11)-(12) are the value constraints of variables.