- 1 - Routing Methods for Twin - Trailer Trucks by Jonathan

This thesis presents a body of initial work on a class of routing problems that resemble classical vehicle routing problems (VRP's), but differ in a few key aspects. A particular subset of this class arises in the regional-level operation of an LTL (Less than TruckLoad) truck line using twin-trailer combinations. Other problems in the class, covered in much less detail, may be useful in planning regional or overall operations of shipping lines, railroads, barge companies, or air freight carriers. Generally, the orientation of the problem model is towards freight carriers who consolidate siipments into large quanta or containers. This practice is currently widespread as it reduces handling costs. The thesis describes a class of regional LTL twin-trailer truck problems, called the "central 2-CFP", contained in a broader class named k-CFP. It presents an aggregate commodity flow formulation of the k-CFP, and analyzes the formulation's LP relaxation via Lagrangean duality. The next topic is a Lagrangean branch and bound method for the central 2-CFP, including computational tests. The thesis closes by suggesting improvements and alternatives to the tested method. Thesis Supervisor: Yosef Sheffi Title: Associate Professor of Civil Engineering