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...
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...
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...
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....
