ITS Berkeley

Handling Operations and the Lot Size Trade-off

Carlos Daganzo
Newell, Gordon F.
1993

This paper presents a handling cost model for a warehouse that supplies one or more stores with a large number of items and examines operating strategies whose objective is to minimize the sum of handling, transportation and inventory costs. Decisions must be made regarding the frequency of shipments to the store(s) (i.e. the transportation schedule) and the specific items and lot sizes included in each shipment. The paper shows that, conditional on a transportation schedule, lot sizes for the different items (i.e. their delivery frequency consistent with the transportation schedule) can...

Restricting Road Use Can Benefit Everyone, Part II: Time-of-Day Restrictions that Encourage Earlier Arrivals

Carlos Daganzo
1992

This research considers a less restricting rationing scheme where a restriction would mean that passage through the bottleneck is banned after a certain time of the day (e.g. the start of the rush hour) but not before that time. Conservatively, we assume that the ban remains in force even after the conclusion of the rush, although in practice one would like to terminate it earlier. (This assumption limits the benefits that can be gained from control as it discourages people from delaying their arrival in order to avoid the queue.) Despite this inefficiency, the scheme is shown to...

Handling Strategies for Import Containers at Marine Terminals

de Castillo, Bernardo
Carlos Daganzo
1993

Many types of storage systems require goods to be stacked in a storage area. The amount of handling effort required to retrieve individual items from the stacks depends on stack heights and on the adopted storage strategy. The paper focuses on container import operations at marine terminals. It presents methods for measuring the amount of handling effort required when two basic strategies are adopted, one that tries to keep all stacks the same size and another than segregates containers according to arrival time. The strategies are compared in an idealized situation. The methods should be...

The Spatial Evolution of Traffic Under the Two Wave Speed Assumption: A Shortcut Procedure and Some Observations

Carlos Daganzo
1993

This paper describes the behavior of traffic in a homogeneous highway according to the hydrodynamic theory, in the special casewhere the flow-density relationship is triangular; i.e. when only two wave velocities exist. It presents an exact formula thatpredicts the vehicle that would be found at position x at time t, given the locations of all the vehicles at time zero. The formula, which does not require identification of the vehicle positions at intermediate times, automatically accounts for the creation and dissipation of any shocks. It can be used to calculate system performance...

The Cell Transmission Model: A Dynamic Representation of Highway Traffic Consistent with the Hydrodynamic Theory

Carlos Daganzo
1994

This paper presents a simple representation of traffic on a highway with a single entrance and exit. The representation can be used to predict traffic's evolution over time and space, including transient phenomena such as the building, propagation, and dissipation of queues. The easy-to-solve difference equations used to predict traffic's evolution are shown to be the discrete analog of the differential equations arising from a special case of the hydrodynamic model of traffic flow. The proposed method automatically generates appropriate changes in density at locations where the...

Moving Queues in Freeway Traffic Networks

Carlos Daganzo
Lin, W. H.
1993

This paper presents the basic building block and some illustrations of a computer program that is currently being developed to predict the behavior of freeway traffic with a macroscopic model. The program, which keeps track of traffic destinations, is based on an approximation of the hydrodynamic theory of traffic flow in which time and space are treated as discrete variables. The program automatically tracks shocks and acceleration waves, and can realistically locate the front and rear end of moving queues within every link. The basic building block is illustrated by means of a...

Technical Note—Two Properties of the Nested Logit Model

Carlos Daganzo
Kusnic, Michael
1993

This paper presents simple formulae for the utility covariances of the nested logit (NL) model, and based on these defines a “scaled tree” that can be used as an aid for the interpretation of estimation results. The paper also shows that the full information log-likelihood function of linear-in-the-parameters NL models is concave in the utility parameters. Thus, conditional on the scaling parameters, full information maximum likelihood (FIML) searches cannot get trapped in local maxima.

Technical Description of NETCELL: General Framework and Data Structure

Lin, Wei-Hua
Carlos Daganzo
1994

This technical note presents a prototype of a freeway network simulation program, NETCELL, currently under development. NETCELL is based on the cell transmission model which captures the dynamic evolution of multicommodity traffic over a freeway network with three-legged junctions in a way that is consistent with the hydrodynamic theory of highway traffic. The report discusses implementation of the prototype program in detail, including cell representation for a freeway network with three- legged junctions data and file structures, inputs and outputs, and some key algorithms...

A Routing Model for Pickups and Deliveries: No Capacity Restrictions on the Secondary Items

Carlos Daganzo
Hall, Randolph W.
1993

This paper examines a routing problem in which vehicles from a single depot cover a large area, where randomly located customers request pickup and delivery service. The paper assumes that each vehicle must serve its deliveries before it collects any pickups, that vehicles do not need to return to the depot between delivery and collection, and that each vehicle can serve at most C deliveries, but an unlimited number of pickups. This paper does not propose a detailed algorithm; rather, it discusses the pros and cons of various broad routing schemes, and quantifies their performance with...

Effect of Modeling Assumptions on Evolution of Queues in a Single Corridor

Carlos Daganzo
Lin, Wei-Hua
1994

A qualitative description is presented of queuing patterns under an idealized scenario analogous to the evolution of traffic congestion during the morning peak hour in a long corridor leading to a single destination. The simplicity of the scenario allows the results to be verified independently by hand. Initially the corridor is assumed to consist of a single freeway. Traffic is generated at the freeway's many on-ramps during a short period and then is assumed to subside. Capacity limitations create queues on the ramps and the freeway, whose evolution is then described. A special...