Chris Caplice

Impact of Bimodal and Lognormal Distributions in Ocean Transportation Transit Time on Logistics Costs

This paper shows that ignoring bimodality and lognormality in transit time distributions can cause large increases in the logistic costs of maritime transportation. Bimodal and lognormal transit time distributions are observed to be of moderate frequency (approximately 17%) but high impact in the volume of shipment carried (approximately 85%) in these lanes. Ignoring and assuming incorrect distribution of transit time can have dramatic implications on the safety stock levels and reorder points and hence inventory cost incurred by the shipper. To display the incorrectness of such assumptions, the paper compares the typical approach of using a deterministic value (Case 1) for transit time and Hadley–Whitin (1963) with normal approximation (Case 2) to the authors’ simulation and empirical analysis on bimodal and lognormal transit time distributions (Case 3). This paper further explores how the shipper should optimally manage inventory in the parameters of transit time distribution and critical ratio (or the service level of the shipper). Specifically, different regions are defined by the transit time distribution parameters and critical ratios that determine the magnitude of relative cost differences when the three cases are compared.

Driving Forces Influencing Future Freight Flows

This interim report summarizes the findings from the first phase of the National Cooperative Highway Research Program (NCHRP) 20-83 (1) project. The objectives of phase 1 were to identify, categorize, and rank the driving forces and critical uncertainties that will influence the future freight transportation flows within the United States over the next 30 years. The results from phase 1 are to be used in phase 2 to help develop the set of future scenarios to utilize in the phase 3 workshops. The report is organized as follows. Section 1 gives an overview of the report. Section 2 provides details on the process and methodology used to uncover the driving forces and critical uncertainties. This includes a discussion of the Future Freight Flows Symposium, a review of the workshop materials tested, and a summary of the Stakeholders survey instrument. Section 3 presents the combined analysis of the results from these activities. Section 4 lays out the next steps by providing an update on Phase 2.

Strategic Issues Facing Transportation, Volume 1: Scenario Planning for Freight Transportation Infrastructure Investment

Major trends affecting the future of the United States and the world will dramatically reshape transportation priorities and needs. The American Association of State Highway and Transportation Officials established the National Cooperative Highway Research Program (NCHRP) Project 20-83 research series to examine global and domestic long-range strategic issues and their implications for departments of transportation (DOTs) to help prepare the DOTs for the challenges and benefits created by these trends. This report, the first report in this series, provides decision makers with a critical analysis of the driving forces behind high-impact economic and social changes as well as sourcing patterns that may affect the U.S. freight transportation system. It also introduces scenario planning as a tool that can be used in conjunction with other planning methods to improve the quality of long-range transportation infrastructure planning. Accompanying the report is a DVD package, CRP-CD-130, containing four future scenarios, as well as a detailed methodology for planners to follow to conduct their own scenario planning workshops.