We introduce a new vehicle routing problem(VRP) variant called
the Multiple Trip Vehicle Routing Problem with Backhauls(MT-VRPB).
The MT-VRPB combines the characteristics of the classical versions of
two VRP problems studied in the literature,i.e.,the MT-VRP in which a
vehicle may perform several routes (trips) within a given time period;
and the vehicle routing problem with backhauls(VRPB) in which a
vehicle may pick up goods to bring back to the depot once the
deliveries are made.Therefore in the MT-VRPB a vehicle may not only
perform more than one trip in a given planning period but it can also
collect goods in each trip. Since the MT-VRP and the VRPB have been
studied independently in the literature ,we first provide a brief
description of these two routing problems