Dincer Konur and Joseph Geunes Department of Industrial and Systems Engineering

Transcription

1 Dincer Konur and Joseph Geunes 1

2 Introduction Literature Review Truckload Transportation Consolidation Concept Problem Formulation Solution Approach Conclusion and Future Work 2

3 Traffic congestion affects supply chains Negative effects on logistical processes McKinnon (1999), Sankaran et al. (2005) Increased delay times, distribution costs Fernie et al. (2000), McKinnon et al. (2008) Traffic congestion hinders efficiency Inefficient usage of transportation network Golob and Regan (2001, 2003), Figliozzi (2009) Inefficient supply chain design Konur and Geunes (2011) Effects of congestion on facility locations and flows 3

4 Freight transportation affects congestion Just-in-Time requires frequent shipments This contributes to increased congestion Rao (1991), Moinzadeh et al. (1997), Crainic et al. (2004) Trucks as a transportation mode Urban freight transportation increases congestion US DOT Federal Highway Administration notes Existing and anticipated increases in the number of trucks threaten system performance 4

5 Avoiding trucks in traffic Toll pricing for trucks, restricted lanes for trucks, truck-only lanes, peak time restrictions for trucks Distribution lacks control and coordination Increased number of unutilized vehicles in traffic Coordination of freight vehicles are studied City Logistics: Coordination design Janssen and Oldenburger (1991), Ruske (1994), Kohler (1997), Crainic et al. (2004) 5

6 Less-than-truckload transportation (LTL) Transportation costs are based on per unit charges Not efficient for the supply chain agent, and can increase number of trucks used Truckload transportation (TL) Transportation costs are based on the number of trucks used for shipment More realistic and improves truck utilization Aucamp (1982), Cetinkaya and Lee (2002), Toptal et al. (2003), Toptal and Cetinkaya (2006) 6

7 We consider consolidation of a set of items with Truckload transportation Consolidation will decrease the number of trucks used for shipments Hence, it will decrease contributions of freight transportation to congestion 7

8 A Multi-Item EOQ Model with Shipment Consolidation and Explicit Truckload Transportation Costs Economic Order Quantity (EOQ) model is used for shipment frequency decisions A supply chain agent needs to control multiple items Third-Party-Logistics providers use trucks We aim to increase utilization of trucks via shipment consolidation while reducing the transportation costs 8

9 Every 20 days 6 trucks per month Every 10 days Every 15 days 4 trucks per month 9

10 Single item case: One can solve the agent s problem when each item is separately controlled Under consolidation: We can minimize the costs associated with consolidated set of items 10

11 Best Consolidation Policy: A set partitioning problem (NP-complete) Branch-and-Price vs. Heuristic methods 11

12 Branch-and-Price: Using column generation in a branch-and-bound tree Solve a pricing problem to generate columns Branch-and-Price for our problem: The pricing problem is NP-hard in its general format A special case can be solved efficiently When items are identical (consolidation of different shipments of the same item) 12

13 Heuristic methods Consolidate items with close frequencies This will reduce truckload transportation costs while avoiding a substantial increase in inventory and setup related costs Cluster items such that the total costs for the items decreases This will decrease the number of trucks used by increasing the utilization of trucks 13

14 We model realistic transportation costs by considering Truckload transportation A set partitioning problem is formulated Branch-and-price algorithm is used Heuristic methods will be studied Impacts of consolidation Truck utilization Number of trucks used for shipments Decrease contributions to congestion Better city logistics 14

15 US DOT FHA notes The nation s truck fleet has grown significantly in number and distance driven Congested highways carrying a large number of trucks substantially impede interstate commerce, and trucks on those segments contribute significantly to congestion Therefore utilization of trucks and decreasing the number of trucks for moving same amount of commodities is important Our approach will contribute to this goal 15

16 Thank You! Any Questions? 16