“…It is known that this model generates only the Pareto-optimal (i.e., nondominated) solutions for every possible weight vector [w 1 , w 2 ], because if there exist multiple optimal solutions that minimize Equation (18), the model selects only the solution which achieves the minimal value of U 1 or U 2 , whichever is nonbinding in Equations (19) or (20) (Ogryczak, 1994). We solve the above lexicographic optimization model to optimality by using the method (algorithm) developed specifically for this study (it is difficult to solve our model by using the standard solution technique, as it combines the resource (time)-constrained SRP and the FRVRP, both of which are known to be NP-hard (e.g., Zhu & Wilhelm, 2007;Suzuki, 2012). This algorithm, which resembles the branch-and-bound enumeration technique, seeks the optimal solution by finding the best refueling policy for all the possible routes between s and d, except for those whose distances are substantially longer than that of the shortest route (such that they cannot theoretically be the route chosen under the optimal solution).…”