Freight and Goods Movement

Counteracting the Bullwhip Effect with Decentralized Negotiations and Advance Demand Information

Ouyang, Yanfeng
Daganzo, Carlos F.
2006

This paper shows how to reduce the bullwhip effect by introducing advance demand information (ADI) into the ordering schemes of supply chains. It quantifies the potential costs and benefits of ADI, and demonstrates that they are not evenly distributed across the chain. Therefore, market-based strategies to re-distribute wealth without penalizing any supplier are presented. The paper shows that if a centralized operation can eliminate the bullwhip effect and reduce total cost, then some of this reduction can also be achieved with decentralized negotiation schemes. Their performance is...

Characterization of the Bullwhip Effect in Linear, Time-Invariant Supply Chains: Some Formulae and Tests

Ouyang, Yanfeng
Daganzo, Carlos F.
2006

The authors analyze the bullwhip effect in multistage, decentralized supply chains operated with linear and time-invariant inventory management policies; the focus is on robustness. The supply chain is modeled as a single-input, single-output control system driven by arbitrary customer demands. The authors derive robust analytical conditions to predict the presence of the bullwhip effect and bound its magnitude, based only on the way inventories are managed. These results hold independently of the customer demand. The authors also characterize the stream of orders placed at any stage of...

Double-Cycling Strategies for Container Ships and Their Effect on Ship Loading and Unloading Operations

Goodchild, Anne V.
Daganzo, Carlos F.
2006

Loading ships as they are unloaded (double cycling) can improve the efficiency of a quay crane and container port. This paper describes the double-cycling problem, and presents solution algorithms and simple formulae to determine reductions in the number of operations and operating time using the technique. We focus on reducing the number of operations necessary to turn around a row of a ship. The problem is first formulated as a scheduling problem, which can be solved optimally. A simple lower bound for all strategies is then developed. We also present a greedy algorithm that yields a...

Continuum Approximation Techniques for the Design of Integrated Package Distribution Systems

Smilowitz, Karen R.
Daganzo, Carlos F.
2007

Complex package distribution systems are designed using idealizations of network geometries, operating costs, demand and customer distributions, and routing patterns. The goal is to find simple, yet realistic, guidelines to design and operate a network integrated both by transportation mode and service level; i.e., overnight (express) and longer (deferred) deadlines. The decision variables and parameters that define the problem are presented along with the models to approximate total operating cost. The design problem is then reduced to a series of optimization subproblems that can be...

Crane Double Cycling in Container Ports: Planning Methods and Evaluation

Goodchild, A. V.
Daganzo, Carlos F.
2007

In this paper we look at the longer term impact of double cycling on port operations including crane, vessel, and berth productivity. Double cycling is a technique by which empty crane moves are converted into productive ones. We use a double cycling sequence that is operationally convenient, easy to model, and nearly optimum. We evaluate the performance of this sequence over single cycling. A framework is developed for analysis, and a simple formula is developed to predict the impact on turn-around time. The formula is an accurate predictor of performance. We show that double cycling can...

Crane Double Cycling in Container Ports

Goodchild, Anne V.
Daganzo, Carlos F.
2008

Loading ships as they are unloaded (double cycling) can improve the efficiency of a quay crane and therefore a container port. This chapter describes the double-cycling problem, presents solution algorithms to the sequencing problem, and provides simple formulae to estimate benefits. We focus on reducing the number of operations necessary to turn around a ship. First an intuitive lower bound is developed. We then present a greedy algorithm that was developed based on the physical properties of the problem and yields a tight upper bound. The formula for an upper bound on the greedy...

Strategies for Successful Implementation of Virtual Weigh and Compliance Systems in California

Regan, Amelia
2006

The California Department of Transportation (Caltrans) is developing a virtual weigh and compliance system (VWCS) for better commercial vehicle monitoring and weight enforcement. The objective of this synthesis is to document recent efforts and technologies associated with the automated monitoring and enforcement of commercial vehicles and to present the current state of the practice in dealing with overweight vehicle enforcement using advanced weigh-in-motion (WIM) technologies.

Who Has Access to E-Commerce During the COVID-19 Pandemic in the Sacramento Region? Implications for Future E-Commerce and Shopping Tripmaking

Forscher, Teddy
Deakin, Elizabeth, PhD
Walker, Joan, PhD
Shaheen, Susan, PhD
2021

The COVID-19 pandemic brought about dramatic shifts in travel, including shopping trips. We investigated changes in eshopping for food and non-food items by supplementing an April to May 2018 household travel survey (n=3,956 households) conducted by the Sacramento Area Council of Governments (SACOG) with a May 2020 follow-on panel survey (n=313 households) during one week early in the pandemic. Results demonstrate that impacts from added pickups and deliveries in the SACOG region during the first two months of the COVID-19 pandemic were limited and did not overwhelm curb management at...

Synthesis of State-Level Planning and Strategic Actions on Automated Vehicles: Lessons and Policy Guidance for California

Wong, Stephen
Shaheen, Susan, PhD
2020

This synthesis provides a summary and comparative analysis of actions states across the United States are taking inresponse to automated vehicles (AVs). The research focuses on state-level stakeholder forums (e.g., task forces, committees) and state-level strategic actions (e.g., studies, initiatives, programs) initiated by a state legislature, agovernor, or a state agency. The analysis found that AV stakeholder forums and strategic actions address a diverse set offocus areas, but they pay minimal attention to the implications of AVs on the environment, public health, social equity, land...

Crane Double Cycling in Container Ports: Affect on Ship Dwell Time

Goodchild, Anne V.
Daganzo, Carlos F.
2005

Loading ships as they are unloaded (double-cycling) can improve the efficiency of a quay crane and thus container port. This paper describes the double-cycling problem, and presents two solution algorithms and simple formulae to estimate reductions in the number of operations, and operating time. The problem is formulated as a scheduling problem. Small problems can be solved to optimality with a standard numerical solver, but problems of typical size are computationally burdensome and terminated after 10 hours with optimality gaps larger than 50%. A formula for an improved lower bound to...