ITS Berkeley

Design of Multiple-Vehicle Delivery Tours—I A Ring-Radial Network

Newell, Gordon F.
Carlos Daganzo
1986

Certain aspects of what is commonly described as the “Vehicle Routing Problem” are discussed. We wish to deliver items to a large number of points randomly distributed over some region by means of vehicles, each of which can deliver to only C points. The key to any detailed routing to minimize the cost of delivery (by hand or computer) is first to partition the region into zones in which individual vehicles make deliveries. We assume here that there are many such zones, an average density of points δ, that the “unit of length” δ-1/2 is large compared with the spacing between roads, and C...

Reducing Logistics Costs at General Motors

Blumenfeld, Dennis E.
Burns, Lawrence D.
Carlos Daganzo
Frick, Michael C.
Hall, Randolf W.
1987

Automobile and truck production at General Motors involves shipping a broad variety of materials, parts, and components from 20,000 supplier plants to over 160 GM plants. To help reduce logistics costs at GM, the decision tool TRANSPART was developed. In its initial application for GM's Delco Electronics Division, TRANSPART identified a 26 percent logistics cost savings opportunity ($2.9 million per year). Today, TRANSPART II—a commercial version of the tool—is being used in more than 40 GM plants.

Design of Multiple Vehicle Delivery Tours—II Other Metrics

Newell, Gordon F.
Carlos Daganzo
1986

The methods described in Part I for a ring-radial metric are generalized to a network having a fine nearly rectangular grid of local roads, but possibly with a few fast roads superimposed. To select delivery zones, one should first draw the equi-travel-time contours from the source and then choose nearly rectangular zones with suitable width and orientation relative to the network grid and the local contour lines. Some illustrations are given for an idealized square grid of roads. In this case the rectangular delivery zones should be oriented at 45° to the grid, perpendicular to the...

Assembly Line Job Sequencing Principles

Burns, Lawrence D.
Carlos Daganzo
1987

Assembly line job sequencing establishes the order in which jobs are processed by an assembly line. This research focuses on job sequencing methods for assembly lines with work stations that receive the same fixed job sequence, are coupled together so that there is no work-in-process storage, and are balanced so that jobs move continuously between them at a constant rate. Automobile assembly lines frequently have these characteristics. Simple analytical principles are derived that aid in evaluating trade-offs between different job sequencing objectives. Included are set-up cost objectives...

Increasing Model Precision Can Reduce Accuracy

Carlos Daganzo
1987

In the field of logistics, a variable that is to be predicted (e.g., cost) often varies in a nonsmooth, irregular, but known manner, with various factors (e.g., distances, quantity, and density of material to be carried, etc.). This paper identifies conditions, where given approximate input factors, a prediction of the variable is less error prone if one uses a smooth approximation to the exact function of the factors. This phenomenon, which is quite prevalent, may enhance the appeal of continuous approximation models in some instances.

Modeling Distribution Problems with Time Windows. Part II: Two Customer Types

Carlos Daganzo
1987

This paper extends the results of a previous study concerning distribution with time windows. It is recognized that customers who do not need to be allocated to a time window should receive different service than the rest. Three strategies were studied to accomplish that: stratified service, discriminating service, and staggered and discriminating service. Of these, the last strategy yields the lowest local distribution distance per customer, a distance which can be less than half that for the strategy explained in the previous paper (joint service). Stratified service, however, can yield...

Optimum Bunker Size and Location in Underground Coal Mine Conveyor Systems

Baral, Suresh C.
Carlos Daganzo
Hood, Michael
1987

The transportation of coal out of a mine is usually done by a serially linked system of conveyors. It is apparent that in a serially dependent system of this type the failure of any one component (conveyor) causes the complete system to be shut down. The provision of bunkers at strategically located points in the conveyor system can result in the production of coal even in the event of failure of some outbye conveyors. Although the use of bunkers can increase mine system availability, the maximum possible system availability may not be attained if the bunker capacity is inadequate and/or...

A Comparison of In-Vehicle and Out-of- Vehicle Freight Consolidation Strategies

Carlos Daganzo
1988

This paper addresses physical distribution problems, in which items have to be distributed from an origin to many destinations, and it examines ways to reduce inventories. Under certain conditions, a peddling strategy with no transshipments is shown to be superior to any strategy with transshipments. Although the conditions leading to this result are not always met, the results suggest that transshipments are undersirable for freight distribution, unless of course they serve a purpose unrelated to inventory. This is contrast with many-to-many shipping operations which, under the same...

Dynamic Blocking for Railyards: Part II. Heterogeneous Traffic

Carlos Daganzo
1987

Traffic through a railroad yard is said to be heterogeneous if all the destinations are not served with the same frequency. This paper presents a study of railroad yards when traffic is heterogeneous and stationary, that is, without rush hour (or rush day) phenomena. Destinations (blocks) are grouped into categories that are served with the same frequency. The number of blocks and the frequency corresponding to each class are the only traffic characteristics that need to be known to analyze a given yard. With this information it is easy to determine the minimum number of tracks needed, and...

Modeling Distribution Problems with Time Windows: Part I

Carlos Daganzo
1987

This paper shows how distribution problems with delivery time constraints can be modeled approximately with just a few variables. Its objective is neither to develop a scheduling algorithm nor an exact predictive method; rather, it is to illustrate some trade-offs and principles that can be used for planning and algorithm development. A workday is divided into time periods. Time windows are modeled by specifying the period in which a vehicle should visit each customer. (The companion paper explores scenarios where many customers do not specify a time window, and thus, it is advantageous...