This paper analyzes the bullwhip effect in decentralized, linear and time-invariant (LTI) supply chains. It generalizes existing results by broadening the class of policies and customer demand processes under consideration. The supply chain is modeled as a single-input, singleoutput control system driven by arbitrary demands. The paper discusses the appropriateness of various metrics for the bullwhip effect, and derives analytical conditions to predict its presence independently of the demand process. The paper also gives a formula for the variance of the order stream at any stage when the...
Double cycling improves efficiency by unloading and loading a ship simultaneously; using wasted crane moves to transport containers. This paper demonstrates that double cycling can reduce ship turn-around time through this efficiency improvement. The paper describes the nature of the double cycling problem and, for a given loading-plan, quantifies the benefits using a greedy algorithm. The relationship between the benefits of double cycling, and the problem parameters is analyzed using simple formulas and a simulation program. This paper demonstrates that double cycling can create...
Multi-vehicle systems are naturally encountered in civil and military applications. Cooperation amongst individual "miniaturized" vehicles allows for flexibility to accomplish missions that a single large vehicle may not readily be able to accomplish. While accomplishing a mission, motion planning algorithms are required to efficiently utilize a common resource (such as the total fuel in the collection of vehicles) or to penalize a collective cost function (such as to minimize the maximum time taken by the vehicles to reach their intended target). The objective of this paper is to present...
In this brief, we explore what might happen were SB 50 to pass by taking a detailed look at local market conditions in four case study neighborhoods. Local context shapes financial and physical feasibility. When SB 827, the predecessor to SB 50, was under consideration, estimates of its impact on new housing supply were optimistic. Yet, most of these estimates focused on aggregate development potential and did not consider the on-the-ground reality of other zoning provisions that may influence development, what types of projects might pencil out, or what the existing stock looks like.
California is one of the largest producers of perishable produce in the world; producing about 25 million tons of fruits and vegetables each year. This sector supports a large transportation industry that handles the exports of these goods. Starting from the 1950’s, the export of produce has gradually shifted modes from rail to trucks. Currently, only 3% of California’s produce is being exported by rail. However, this share has begun to increase due to efforts in private industry to monetize this space, with total rail tonnage exceeding one million for the first time in decades starting in...
This report compares the performance of three double-cycling algorithms used to determine the sequence with which to load and unload containers from a vessel with a quay crane. Double cycling is a technique which can improve the efficiency of a quay crane and container port by unloading and loading containers in the same crane cycle. The three algorithms, the greedy strategy, the proximal strategy, and Johnson’s rule, are introduced and results from applying the three strategies to a set of simulated vessels are compared. While Johnson’s rule provides the minimum number of cycles required...
Truck-based transportation is the predominant mode used to transport goods and raw materials within the United States. While trucks play a major role in local commerce, a significant portion of truck activity is also long haul in nature. Long-haul truck drivers are continuously faced with the problem of not being able to secure a safe parking spot since many rest areas become fully occupied, and information about parking and availability is limited. Truck drivers faced with full parking lots/facilities either continue driving until a safe parking spot is located or park illegally....
The Program on Advanced Technology for the Highway (PATH), has been established in response to funding by the United States Congress and the California Legislature to demonstrate how "high technology" might be applied to improve highway transportation. PATH's goal, in the short run, is to implement technologies which promise significant relief of acute problemsincluding traffic congestion, air pollution and energy use. Alternative systems of vehicle guidance and control, navigation, propulsion, and communication will be studied and/or developed. The impacts of these systems on highway...
This paper extends previous research on Computer Integrated Transportation (CIT) to commercial vehicle operations (CVO), specifically to examine how government can work with trucking companies within a CIT framework. The research entailed a review of how government currently interacts with trucking companies, interviews with trucking terminal managers, and case-studies on terminal operations at five of the nation's largest motor carriers. Opportunities are identified in the area of unifying interaction between government and industry and in the area of in- vehicle devices for automated...
Traffic congestion and trucking activities in the San Francisco Bay Area are increasing due to the rapid population growth and economic expansion. It is imperative to explore transportation alternatives, and the Bay Area Rapid Transit (BART) system, with 63 percent unused capacity on average in non-peak hours, presents such an opportunity. If BART’s service is extended to include air-freight movement, extra revenue can be generated, truck miles travelled on highways will be reduced (potentially leading to a reduced traffic congestion and pollution), and traffic safety could be improved....
