bluuebunny/crossref_metadata_2025 huggingface dataset:
Network Median Problems with Continuously Distributed Demand
Authors: Nkansah Paul T. , David H. T.
Published: October 2008

The network p-median (supply point location) problem has been generalized to the case where demand is continuously distributed. For p = 1 and uniformly distributed demand, and with the objective of minimizing distance, the interior points of an “edge” may be omitted from the search for an optimal supply point when that edge belongs to a “circuit.” Analogous conditions apply when demand is distributed in other than uniform fashion, and/or the objective is to minimize various forms of travel cost. In the case of p ≥ 2, with uniformly distributed demand and with the objective of minimizing distance, p-tuples of supply points, whose components are, respectively, interior points of p “mutually distant” edges, can be omitted from the search for p optimal supply points.
Average Delay at an Unsignalized Intersection with Two Major Streams Each Having a Dichotomized Headway Distribution
Authors: Troutbeck R. J.
Published: October 2008

The average time a driver has to wait before he can cross two major streams has been a major performance indicator for unsignalized intersections. The equations presented in this paper give an estimate of this average delay as a function of the average delay to isolated minor stream vehicles (Adams' delay) and the degree of saturation of the minor stream (minor stream entry flow/maximum entry flow) and a form factor (which quantifies the effect of queueing in the minor stream). It was assumed that drivers were consistent and homogeneous and that headways in each major stream were independent of other headways in the same stream and in the other stream. Although the concepts were described in general terms, equations for the maximum minor stream entry flow and Adams' delay were developed assuming that the headways in the major stream to have a dichotomized distribution as given by R. J. Cowan in 1975. Tanner's equations can be used to calculate the form factor when there is a single major stream and when the minor stream headways are Poissonian. For other conditions, a computer simulation program was used to give estimates of the form factor which give satisfactory estimates of average delay for practical purposes. The discussion in this paper indicates that the degree of bunching in the major streams has a major effect of Adams' delay, average delay and the maximum minor stream entry flow.
On a Paper by Andre de Palma, Moshe Ben-Akiva, Claude Lefèvre, and Nicolaos Litinas Entitled “Stochastic Equilibrium Model of Peak Period Traffic Congestion”
Authors: Hurdle Vanolin F.
Published: October 2008

A paper published in 1983 in this journal by A. de Palma et al. uses a deterministic queueing supply model in combination with a random utility demand model to predict the pattern of traffic flows during a peak period. Two different versions of the supply model are included, a “basic model” which is identical to the supply model used by a number of other authors investigating the same general problem (e.g., M. J. Smith [Smith, M. J. 1984. The existence of a time-dependent equilibrium distribution of arrivals at a single bottleneck. Trans. Sci. 18 385–394.]), and a more complicated “extended model.” As detailed below, there is a mathematical discrepancy in the analysis. Because of this discrepancy, some of the conclusions about the traffic flow pattern in the case of the extended model are incorrect and all are unproven. For the simpler—and seemingly more realistic—basic model, the discrepancy vanishes and the conclusions remain valid.
Comprehensive Design of Highway Networks
Authors: Trietsch Dan
Published: October 2008

In this paper, the sequel to “A Family of Methods for Preliminary Highway Alignment,” we apply results from the latter, in addition to some network design models which include locating road junctions (“Generalized Steiner Points”) to the design of complete highway networks connecting n given points on any given terrain. The objective is to satisfy given bilateral transportation demands at minimal total cost—including construction and users' costs.
Optimum Zone Configuration for Planned Urban Commuter Rail Lines
Authors: Ghoneim Nadia S. A. , Wirasinghe S. C.
Published: October 2008

The optimum zone structure for a planned urban commuter rail line with one to many or many to one type demand during peak periods is analyzed. The objective is to minimize the passenger time costs as well as the relevant system operating and capital costs. The analysis is based on the interaction of a range of variables such as the number of zones, zone boundaries, uniform station spacings, fleet size and train headway. The approximately optimum values of the decision variables are determined mostly in closed form. A numerical application and sensitivity analyses are presented.
Generalized Hierarchical Facility Locations
Authors: Mirchandani Pitu B.
Published: October 2008

This note presents an improved formulation of the hierarchical facility location-allocation problem. It is a generalized model in the sense that the rules for allocating demand types to facility types are general and the “successively inclusive,” “successively exclusive” and “locally inclusive-successively exclusive” allocations that have appeared in the literature are special cases of this model.
Survey Paper—Airline Yield Management An Overview of Seat Inventory Control
Authors: Belobaba Peter P.
Published: October 2008

The seat inventory control component of airline yield management is examined, with an emphasis on the practical aspects of the problem. A survey of current airline practice indicates that seat inventory control is dependent on human judgment rather than systematic analysis. Past work on the development of mathematical methods in this area has focused on large-scale optimization models and simplified representations of the problem. There remains a need for practical solution approaches that incorporate quantitative decision tools.
Modeling Distribution Problems with Time Windows. Part II: Two Customer Types
Authors: Daganzo Carlos F.
Published: October 2008

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 a lower line-haul distance per customer than staggered and discriminating service. In a specific case, a numerical comparison between stratified service and staggered and discriminating service should determine the overall best choice. This choice notwithstanding, the best strategy involves overlapping vehicle tours. The conventional wisdom of dividing customers into non-overlapping clusters for vehicle routing does not seem attractive for distribution problems with time windows.
Comment on “Network Median Problems with Continuously Distributed Demand”
Authors: Batta Rajan , Palekar Udatta S.
Published: October 2008

The purpose of this note is to clarify a result in Nkansah and David's study on network median problems with continuously distributed demand, and to establish a result to effectively deal with edges that do not belong to any circuit.
Aircraft Flow Management under Congestion
Authors: Andreatta G. , Romanin-Jacur G.
Published: October 2008

Airport congestion is one of the main causes of costly aircraft delays. Sometimes costs may be reduced by imposing on some aircraft a delay at take off time in order to later avoid a more expensive airborne delay. The objective of the Flow Management Problem (F.M.P.) is to find an optimal delay strategy so that the total expected delay cost is minimized. In this paper an idealized and greatly simplified version of F.M.P. is investigated. In particular the airways network considered is star-shaped and congestion is allowed only in the central (arrival) airport. For this particular version a model is presented and a polynomial solution algorithm is derived. Landing priorities among aircraft can also influence the total expected delay cost: the optimal priority rule for our version of the F.M.P. is derived. Another algorithm is presented for the case where the number of aircraft not to be delayed on the ground is given a priori. Possible extensions of the proposed model to more realistic situations are mentioned.
Equilibrium Arrivals in Queues with Bulk Service at Scheduled Times
Authors: Glazer A. , Hassin R.
Published: October 2008

In a queuing system that does not serve each customer immediately upon his arrival, a risk-neutral customer will attempt to arrive at a time that minimizes the expected length of his wait. The consequences of such behavior are explored for a queue with scheduled service.
Passenger Delay in a Rapid Transit Station
Authors: Hall Randolph W.
Published: October 2008

An analytical queueing model for predicting passenger delay in a busy rapid transit station is developed and tested. The model accounts for the “lumpy” arrival pattern of passengers exiting trains. Passenger delay is divided into two components: “standard” delay and “interference” delay. Standard delay is the delay incurred when all of the passengers on a train are served before the next train arrives. Interference delay is the added delay when the next train arrives before all of the passengers are served. When a station serves two equally busy tracks, the standard delay per passenger is proportional to the headway and the utilization (arrival rate divided by service rate). The interference delay per passenger is proportional to the headway and the square of the utilization. The size of the headway reflects the “lumpiness” of the arrival pattern. When the headway is small, passengers arrive at a nearly constant rate and delay per passenger is small. When the headway is large, passengers arrive in larger lumps and delay per passenger is large.
A Combined Trip Generation, Trip Distribution, Modal Split, and Trip Assignment Model
Authors: Ali Safwat K. Nabil , Magnanti Thomas L.
Published: October 2008

Modeling of transportation systems must invariably balance behavioral richness and computational tractability. In this paper, we develop a transportation equilibrium model and an algorithm for the simultaneous prediction of trip generation, trip distribution, modal split, and trip assignment on large-scale networks. The model achieves a practical compromise between behavioral and computational aspects of modeling the problem. It is formulated as an equivalent convex optimization problem, yet it is behaviorally richer than other models that can be cast as equivalent convex programs. Although the model is not as behaviorally rich as the most general equilibrium models, it has computational advantages. The applications reported in this paper of the model to real systems, i.e., the intercity transport network of Egypt and the urban transportation network of Austin, Texas, illustrate the computational attractiveness of the approach. These results indicate that equivalent optimization formulations are not as restrictive as previously thought, and hence, the equivalent convex programming approach for modeling and predicting equilibrium on transportation systems remains a viable and fruitful avenue for future consideration.
Predicting Dispatching Delays on a Low Speed, Single Track Railroad
Authors: Greenberg Betsy S. , Leachman Robert C. , Wolff Ronald W.
Published: October 2008

This paper presents queueing models for predicting dispatching delays on single track, low speed rail lines with widely spaced passing locations. Because of scheduling unpredictabilities, we assume Poisson arrivals of trains. Because of the slow transit speeds, we assume that trains traveling in the same direction can do so on close headways. We also assume siding capacity at passing locations is not limiting. Under these assumptions, we calculate expected delays on individual segments of single track and for segments of single track with an alternate route.
Multiple Equilibrium Behaviors on Networks
Authors: Harker Patrick T.
Published: October 2008

Models of traffic networks typically assume that the consumers of the transportation service either behave in a totally noncooperative (user equilibrium) or cooperative (system equilibrium) manner. This note presents a model in which each origin-destination pair can obey either behavioral principal. After discussing the issues of existence and uniqueness and the model's applicability to freight and urban transportation applications, it is shown how variational inequality methods can be employed to solve this new model. A small example is then used to illustrate the features of a multiple behavior traffic network equilibrium.
Traffic Flow for the Morning Commute
Authors: Newell G. F.
Published: October 2008

We imagine that drivers in the morning commute must traverse some homogeneous section of highway of length l > 0 and finite capacity qm to reach their workplaces. Each driver has a specified latest time at which he can exit the road and still be at work on time, but, because of the capacity and other traffic flow restrictions, it may be necessary that some drivers be at work earlier than their scheduled times if no one is to be late. Traffic is treated as a continuous fluid in the manner proposed by Lighthill and Whitham. This represents a generalization to l > 0 of a theory described by Hendrickson and Kocur for point bottlenecks (l = 0) and a revision of a theory presented by Mahmassani and Herman. That waves can travel with only finite speed causes the schedule delay to be larger for l > 0 than for l = 0 and possibly be positive even if the demand rate is always less than qm. The conclusions, however, are quite different from those given by Mahmassani and Herman. If there is a cost per unit of trip time and another (lower) cost per unit of schedule delay, there is a well-defined system optimal assignment. There is some question, however, regarding the stability of the user optimal assignment.
Parametric Facility Location on a Tree Network with an Lp-Norm Cost Function
Authors: Brandeau Margaret L. , Chiu Samuel S.
Published: October 2008

This paper examines the optimal location of a single facility on a tree network with the objective being to minimize the sum of weighted distances from each node measured by an Lp-norm-based cost function. Our goal is to trace the trajectory of the optimal location when the Lp-norm parameter p varies from one to infinity. Convexity of the objective function, when p is fixed, allows us to perform the parametric analysis. We characterize possible trajectory paths, and show that some surprising trajectory results can occur.
A Capacitated, Balanced, 2-Median Problem on a Tree Network with a Continuum of Link Demands
Authors: Sherali Hanif D. , Nordai Frederick L.
Published: October 2008

This note considers the problem of locating an absolute 2-median on an undirected tree network having discrete nodal demands as well as a continuum of link demands. The service facilities are assumed to have known finite capacities which sum to the total demand on the network. For this capacitated, balanced case, we derive certain necessary optimality conditions which admit useful localization results. These results permit us to identify and characterize a reduced, finite set of candidate solutions which may be compared to obtain an optimal 2-median for the problem.
Bibliographic Section
Authors: Miller Eric J. , Patterson Philip D. , Kostyniuk Lidia P. , Viton Philip A. , Anas Alex
Published: October 2008

Qualitative Choice Analysis: Theory, Econometrics, and an Application to Automobile Demand, by Kenneth Train, The MIT Press, Cambridge, Mass., 1986, 252 pp—reviewed by Eric J. Miller.

Regulating the Automobile, by Robert W. Crandall, Howard K. Gruenspecht, Theodore E. Keeler and Lester B. Lave, Brookings Institution, Washington, D.C., 1986, 202 pp—reviewed by Philip D. Patterson.

New Survey Methods in Transport, by E. S. Ampt, A. J. Richardson and W. Brog (eds.), VNU Science Press, Utrecht, The Netherlands, 1985, 367 pp—reviewed by Lidia P. Kostyniuk.

The Economic Effects of Airline Deregulation, by Steven Morrison and Clifford Winston, The Brookings Institution, Washington, D.C., 1986, 84 pp. + xi—reviewed by Philip A. Viton.

Advances in Urban Systems Modeling, by Bruce Hutchinson and Michael Batty (eds.), Elsevier, North-Holland, Amsterdam, 1986, 432 pp. + xi—reviewed by Alex Anas.
On the Steady-State Solution of the M/C2(a, b)/s Queueing System
Authors: Bertsimas Dimitris , Papaconstantinou Xenophon
Published: October 2008

This study solves the bulk queueing system M/C2 (a, b)/s with Poisson arrivals and service time pdf of Coxian-2 type. When a server becomes free a group of customers of size at most b can be served. The server is not allowed to process a group of size less than a, 1 ≤ a ≤ b. Using the generalized method of stages, an explicit form is found for the probabilities of states with all servers busy and then through a recursive structure the problem is reduced to a linear system of s + 1 equations with s + 1 unknowns. An O(as3) algorithm is proposed. Closed form expressions for the waiting-time, idle-servers and service-batch distributions are derived.
Finding the Optimal a Priori Tour and Location of a Traveling Salesman with Nonhomogeneous Customers
Authors: Berman Oded , Simchi-Levi David
Published: October 2008

This paper deals with the following routing problem: on any given day a subset of k out of n nodes of a network require a service visit (0 ≤ k ≤ n). Each node of the network can generate a request with a given probability. The problem is to find an a priori tour with a minimum expected length through the n nodes such that any k given nodes will be visited in the same order they appear in the a priori tour. In contrast to other work, the probabilities of placing a demand at the different nodes are allowed to differ one from the other. Also discussed is the problem of finding the optimal home location (origin) for the service unit.
On the Location of Hub Facilities
Authors: Aykin Turgut
Published: October 2008

Hub Location problems have attracted considerable attention recently. In this note the multihub location problem is formulated and the condition under which a destination is optimally assigned to a hub facility is developed.
Transporting Sludge to the 106-Mile Site: An Inventory/Routing Model for Fleet Sizing and Logistics System Design
Authors: Larson Richard C.
Published: October 2008

This paper develops a model that is being used by the City of New York to design a new logistics system to transport municipal sewage sludge from city-operated wastewater treatment plants to a new ocean dumping site 106 miles offshore. The model provides an integrative framework for considering such strategic planning issues as fleet sizing, choice of vessel size, sizing local inventory holding capacities, and analyzing system behavior with and without transshipment. A unique feature of the model is that plant visitation frequencies are determined naturally by the characteristics of the problem (vessel size, inventory holding capacities, statistics of sludge production, proximity of other plants), rather than stated as exogeneous constraints. The formulation should be useful in a more general class of depot-to-customer distribution systems, including the distribution of industrial gases. The paper concludes with a description of additional research that is required in refining both the assumptions and the mechanisms of execution of the model.
Locating Two Facilities on a Tree Subject to Distance Constraints
Authors: Erkut E. , Francis R. L. , Lowe T. J.
Published: October 2008

We wish to locate two new facilities on a tree network, where demands occur at vertices. We minimize any convex function which is nondecreasing in two related single facility convex objective functions, and in the distance between the facilities, subject to a distance constraint imposing an upper bound on the distance between the facilities, as well as to distance constraints imposing upper bounds on the distances between the new facilities and the demand points. We consider both vertex-restricted and vertex-unrestricted problem versions, and, for the latter problem, reduce the location problem when the constraint is tight to a problem of locating a single new facility on a path.
Single Server Queueing-Location Models with Rejection
Authors: Batta Rajan
Published: October 2008

This paper considers the problem of locating a single server on a network while explicitly accounting for queueing of calls for service. Calls from a node can either all be accepted or all be rejected by the service system. Two models are considered. In the first model a call can be rejected independent of the state of the system when the call arrives. In the second model, an arriving call can be rejected only if it finds the server busy. The queueing systems are analyzed for both models. A greedy heuristic is developed which, parametrically in the arrival rate of calls, determines the location of the server and the rejection strategies at nodes. Extreme case analysis with respect to the arrival rate is investigated. A numerical example illustrates our results. Our major observation is that the rejection strategies for calls are dependent on the arrival rate, and the choice of model.
Establishing Continuity of Certain Optimal Parametric Facility Location Trajectories
Authors: Brandeau Margaret L. , Chiu Samuel S.
Published: October 2008

Parametric elements arise naturally in many facility location problems. In this note we establish that if the objective function for a single-server parametric location problem is strictly convex in a certain sense, and if the objective function possesses certain reasonable continuity properties, then the parametric trajectory of the optimal location is continuous.
The Design of a Hierarchical Transportation Network with Transshipment Facilities
Authors: Current John R.
Published: October 2008

In this paper an integer linear program is formulated to identify the least cost two-level hierarchical network. This network must include a primary path from a predetermined starting node to a predetermined terminus node. In addition, each node not on the primary path must be connected to some node on that path via a secondary path. Transshipment facilities are required at the intersections of the primary and secondary paths. Consequently, the formulation directly considers the number and locations of transshipment facilities in determining the minimal cost network. A heuristic is presented which employs a K Shortest Path algorithm and a Minimum Spanning Tree algorithm. Heuristic results of two sample problems are presented and compared to the results obtained by solving the integer LP formulation.
Graphical Interpretation of the Transportation Problem
Authors: Hall Randolph W.
Published: October 2008

The objective of the “transportation problem” is to minimize the cost of satisfying customer product requirements without exceeding supplier capacities. This paper examines the transportation problem with the purpose of ascribing graphical meaning to the solution. The paper summarizes prior results as well as provides new results relative to supplier lattice structures and nonlinear costs.
Conditional p-Center Problems
Authors: Drezner Zvi
Published: October 2008

It is shown that conditional p-center problems can be solved by solving O(log n) p-center problems where n is the number of demand points. Therefore, once an efficient algorithm exists for the p-center problem (by any metric or on a network), then an efficient one can be built for the conditional version of the problem.
On the Equivalence of Competitive Transportation Markets and Congestion in Spatial Price Equilibrium Models
Authors: Jones Philip C. , Theise Eric S.
Published: October 2008

In this paper we explicitly incorporate competitive markets for transportation services into the framework of spatial price equilibrium modeling. These markets can be purely local, purely global, or a combination thereof. We show that the existence of markets for transportation services is equivalent to the existence of congestion in a spatial price equilibrium model. In addition, we give general suggestions regarding the application of these models.
The Equilibrium Worth of a Network Link
Authors: Frank Marguerite
Published: October 2008

Select an arbitrary link T on a directed network whose link costs are fixed, unknown, differentiable disutility functions of link flows (with a symmetric Jacobian). We induce graded variations in the “intrinsic” cost of T due to its own flow by varying the coefficient vector α of a control polynomial pT of this flow. Our sensitivity analysis of such perturbations on the unevaluated equilibrium cost C, for any O(rigin)/D(estination)-pair with arbitrary demand, focuses on the marginal contribution to C of T's equilibrium flow UT. This “shadow price” of UT, as well as the gradient components of C relative to α, are all positive multiples—identical for every O/D-pair-of the rate of change of UT relative to that O/D-pair's demand; and they can all be determined from output-data obtained locally at T. For affine link costs, the shadow price of UT remains constant on every utilized (sub)network as α and O/D-demand both vary, and T-local data then yields a polygonal map with which to predict the resulting link utilization patterns and the variations of C at large.
On the Vector Assignment p-Median Problem
Authors: Hooker J. N. , Garfinkel R. S.
Published: October 2008

The vector assignment p-median problem allows nodes of a network to be served by a nonclosest facility. We present a counterexample to a proposition of J. R. Weaver and R. L. Church that an all-node solution always exists. We show that the proposition is true, however, if every node is served by closer facilities at least as often as by more distant facilities.
Approximate Expressions for Queueing Systems with Scheduled Arrivals and Established Service Order
Authors: Sabria Federico , Daganzo Carlos F.
Published: October 2008

This paper studies single server queueing systems where customers arrive according to a schedule, but not punctually, and where service might be provided in the scheduled order; thus, customers may leave the system in a sequence different to that of their arrivals. The situation arises in connection with maritime container terminals. The steady state solution to the problem follows an integral equation that may be solved numerically. When congestion is light (as is usual in well managed ports) approximate analytic solutions to the integral equation can be found. As an illustration, formulas are given that apply if the deviations from the schedule and the service times have some specific distributions. These expressions accurately predict the expected delay for systems with fairly unpunctual arrivals and occasional congestion. The paper also contains an exact analytical solution for the special case in which service times are constant and the deviations from the arrival schedule are independent Gumbel variables.
Vehicle Routing with Stochastic Demands: Properties and Solution Frameworks
Authors: Dror Moshe , Laporte Gilbert , Trudeau Pierre
Published: October 2008

This paper considers the vehicle routing problem with stochastic demands. The objective is to provide an overview of this problem, and to examine a variety of solution methodologies. The concepts and the main issues are reviewed along with some properties of optimal solutions. The existing stochastic mathematical programming formulations are presented and compared and a new formulation is proposed. A new solution framework for the problem using Markovian decision processes is then presented.
The Dispersion of the Stopping Probability Function
Authors: Prashker J. N. , Mahalel D.
Published: October 2008

This paper points out the relationship, in traffic signals, between the length of the warning period, and the dispersion of the stopping probability function. It is demonstrated with empirical evidence that a long warning period for the termination of the green light causes an increase in the dispersion of the stopping probability function and in the indecision zone. It is argued that the probability for rear-end collisions might also increase.
Bibliographic Section
Authors: Chang Gang-Len , Harker Patrick T. , Janson Bruce N. , Dendrinos Dimitrios S.
Published: October 2008

The Geography of Urban Transportation, edited by Susan Hanson, Guilford Publications Inc., New York, 1986, 424 pp—reviewed by Gang-Len Chang.

Multicriteria Optimization in Engineering and in the Sciences, edited by Wolfram Stadler, Plenum Publishing, New York, N.Y., 1988—reviewed by Patrick T. Harker.

Evaluation Methodologies for Transport Investment, Michael S. Roe, Avebury Books (Gower Publishing Company, Ltd.), Aldershot, England, 1987—reviewed by Bruce N. Janson.

Urban Systems: Contemporary Approaches to Modelling, edited by C. S. Bertuglia, G. Leonardi, S. Occelli, G. A. Rabino, R. Tadei, and A. G. Wilson, Croom Helm, 1987, 677 pp—reviewed by Dimitrios S. Dendrinos.
A Multimode Multiproduct Network Assignment Model for Strategic Planning of Freight Flows
Authors: Guélat Jacques , Florian Michael , Crainic Teodor Gabriel
Published: October 2008

We present in this paper a normative model for simulating freight flows of multiple products on a multimodal network. The multimodal aspects of the transportation system considered are accounted for in the network representation chosen. The multiproduct aspects of the model are exploited in the solution procedure, which is a Gauss–Seidel-Linear Approximation Algorithm. An important component of the solution algorithm is the computation of shortest paths with intermodal transfer costs. Computational results obtained with this algorithm on a network that corresponds to the Brazil transportation network are presented. Several applications of this model are reported as well.
Technical Note—Conditional Location Problems on Networks
Authors: Berman Oded , Simchi-Levi David
Published: October 2008

In this paper, we describe an algorithm to solve conditional location problems (such as the conditional p-median problem or the conditional p-center problem) on networks, where demand points are served by the closest facility whether existing or new. This algorithm requires the one-time solution of a (p + 1)-unconditional corresponding location problem using an appropriate shortest distance matrix.
Scheduling of Extraboard Operators in Transit Systems
Authors: Koutsopoulos Haris N.
Published: October 2008

High levels of absenteeism and uncertainty about the amount of work to be performed force transit agencies to employ more operators than needed to ensure delivery of scheduled service reliably. The efficient utilization of these extra operators (extraboard) is very important and has two aspects: a) the determination of the daily number of extraboard operators (both full time and part time) needed and b) the assignment of report times to these extraboard operators. Models are presented which take into account the operating characteristics of transit systems and result in “optimal” utilization of available resources. A case study demonstrates that the results obtained by using these models are superior to the rules of thumb widely used by the industry, or to simple deterministic models.
Fleet Size Planning when Outside Carrier Services Are Available
Authors: Klincewicz John G. , Luss Hanan , Pilcher Martha G.
Published: October 2008

The delivery of goods from a warehouse to local customers is a critical aspect of a material logistics system. A strategic decision must be made periodically (e.g., once a year) whether to maintain a private delivery fleet, to employ outside commercial carrier services, or to use a combination of both options. We seek to develop a methodology to address this long range planning decision. Our model considers a geographic area, with random daily demands, served by a single warehouse. The costs considered include the fixed and variable (per mile) costs of a private vehicle and the outside carriers' delivery charges. A private vehicle is constrained by the length of the work-day, since it returns to the warehouse only after completing all its deliveries. Since actual customer locations change from day to day, for planning purposes we divide the geographic area into sectors and decide how best to serve each sector. The model determines the private fleet size and the specific assignment of each sector to a private vehicle or to an outside carrier. The centerpiece of our solution approach consists of a single-source capacitated facility location formulation, in which each “customer” (sector) is served by a single “facility” (private vehicle or outside carrier). Computational results are reported.
The Productivity of Multipurpose Seaport Terminals
Authors: Daganzo Carlos F.
Published: October 2008

This paper studies the peculiar queueing problem that arises at multipurpose port terminals serving two traffic types. Primary (liner ship) traffic obeys a schedule and has absolute priority on the use of the multipurpose facilities. Secondary (tramp) traffic, which arrives at random, can also be served elsewhere in the port. Secondary traffic is routed to the multipurpose berths only if doing so does not delay any primary ship. (The port knows a fair amount ahead of time the arrival times of these ships and the likely service times of both liners and tramps). The goal is to obtain simple analytical formulas for the multipurpose terminal's productivity, and for the resulting changes in berth utilization outside the terminal. Although the suggested strategy for routing secondary traffic leads to a queueing problem that is too complicated to yield a simple exact formula, an approximate solution for heavy tramp traffic was found. An exact numerical solution for arbitrary traffic levels, which only applies when liner operations are perfectly regular and deterministic, was also found. In this latter case, because the solution could be expressed as a function of only two parameters, it was possible to present it in graphical form and to obtain a simple analytical expression fitting the graphs.
Commuters' Paths with Penalties for Early or Late Arrival Time
Authors: de Palma André , Hansen Pierre , Labbé Martine
Published: October 2008

We formulate the choice of a best path for a commuter leaving his/her home at a given time and willing to arrive at his/her destination within a given time interval. The objective function integrates constant costs for use of arcs, travel times and schedule delay. The travel times along arcs, which depend on exogenous congestion, are represented by functions of the arrival time at the origin node of the arc. The schedule delay is taken into consideration by penalizing arrival time at the destination outside the desired time interval. The problem is shown to be NP-hard, polynomial subcases are determined and a pseudo-polynomial algorithm is provided for the general case.
Mean-Variance Location Problems
Authors: Berman Oded
Published: October 2008

In this paper we discuss three mean-variance location problems. Two of them are constrained problems where one performance measure—mean of the weighted distance, or variance, is minimized subject to an upper bound constraint on the value of the other. In the third problem the objective function minimized is given by the mean plus a constant times the variance. The paper includes polynomial time algorithms to solve the three problems. The solutions produced by these algorithms are Pareto optimum solutions (solutions that are strictly better than any other solution in at least one of the two measures: mean and variance).
In Memoriam—Leslie C. Edie, 1914–1990
Authors: Gazis Denos C. , Herman Robert
Published: October 2008

Leslie C. Edie, 1914–1990, one of the early pioneers in the fields of operations research and transportation science, was also one of the earliest members of ORSA, and a founding member of the ORSA Transportation Science Section (TSS). He served as the second Chairman of TSS which became the model of all the other ORSA Sections created over the years. In 1964, he worked with D.C.G. who was then TSS Chairman, to set in motion the process for the creation of the first topical journal of ORSA, Transportation Science, of which R.H. served as the founding Editor. In 1972 he was President of ORSA, having served previously as a member of the ORSA Council and several ORSA Committees.
The Capacitated Traveling Salesman Location Problem
Authors: Simchi-Levi David
Published: October 2008

The capacitated traveling salesmen location problem is the problem of locating one service station with servers, each having a limited capacity, q. The service units must visit each day all the calls that are registered in a service list. Each call is generated with a given probability and the service list contains at most n calls. In the paper we present an O(n3) time heuristic for the problem on networks. This heuristic finds a solution whose relative worst-case error equals 3/2−3/(2q). We also show how one can use this heuristic to solve the problem on the plane with rectilinear or Euclidean distances with the same worst-case error. In the latter case the heuristic is proved to be asymptotically optimal.
Technical Note—An Algorithm for Determining Whether m Given Demand Points Are on a Hemisphere or Not
Authors: Tsai Wen-Hsien , Chern Maw-Sheng , Lin Tsong-Ming
Published: October 2008

Location problems on a sphere can be solved easily by mathematical programming or geometrical methods if it is known that all the demand points are located on a hemisphere. This paper presents an algorithm for determining whether m given demand points are on a hemisphere or not. In this algorithm, the great circle is rotated successively until the hemisphere which contains the m given demand points is found or it becomes known using our criteria that the m given demand points are not on a hemisphere. The convergence of this algorithm is proved, and two illustrative examples are presented.
An Integrated Network/Planar Multiobjective Model for Routing and Siting for Hazardous Materials and Wastes
Authors: List George , Mirchandani Pitu
Published: October 2008

Dealing with hazardous materials and wastes has become a problem of major concern for countries throughout the world. This paper presents a model useful in making routing decision, for either material or waste shipments, and siting decisions for waste treatment facilities. Risk, cost, and risk equity are considered jointly in a multiobjective framework. Costs are treated as link attributes while risks, from both transport and treatment, are zonal attributes, pertaining to nonoverlapping geographic areas spread out over the plane. Risks accrue within these zones, due to shipments crossing nearby links or wastes being processed, stored or disposed of at nearby treatment facilities. Total risk is the sum of the zonal risks. Equity is measured as the maximum zonal risk per unit population. Shippers will find the model useful in optimizing their logistics plans. Government agencies will find it helpful in determining how regulations should be set to obtain publicly desirable routing and siting patterns. The model is described in detail and applied in simplified form to an illustrative problem.
The Simultaneous Origin-Destination Assignment and Vehicle Routing Problem
Authors: Soumis François , Sauvé Michel , Le Beau Louis
Published: October 2008

The problem we consider is that of preparing a minimum cost transportation plan by simultaneously solving the following two subproblems: first the assignment of units available at a series of origins to satisfy demand at a series of destinations and second, the design of vehicle tours to transport these units, when the vehicles have to be brought back to their departure point. We present a solution method for this problem using a minimum cost flow model followed by heuristic tour construction and improvement procedures. This approach allows large problems to be solved quickly, and solutions to large test problems have been shown to be 1% or 2% from the optimum. Results are presented for a problem involving the transport of 24,000 students working on an environmental cleanup project.
A Network Design Algorithm Using a Stochastic Incremental Traffic Assignment Approach
Authors: Chen Mingyuan , Alfa Attahiru Sule
Published: October 2008

In this paper, a branch and bound algorithm is presented for solving network design problems (NDP). Route selection for the NDP is based on a stochastic incremental traffic assignment approach. Experiments are performed to compare the behaviors of three assignment methods. Numerical examples are presented to illustrate the algorithm for solving the NDP.
An Optimal Algorithm for Weighted Minimax Flow Centers on Trees
Authors: Eiselt Horst A. , Gendreau Michel
Published: October 2008

Let a tree be given with supplies assigned to its nodes and weights assigned to its edges. The problem considered here is to locate a facility, so that the flow pattern which results from shipping all supplies to the facility, is such that it minimizes the largest weighted flow on any individual edge. First some properties of such facility locations are derived and then a linear time algorithm for their determination along with the associated flow pattern is given.
A Newton-SOR Method for Spatial Price Equilibrium
Authors: Marcotte Patrice , Marquis Gérald , Zubieta Lourdes
Published: October 2008

In this paper we propose an efficient Newton-SOR algorithm for solving the separable spatial price equilibrium problem. Although an active set strategy is implemented for solving for blocks of variables associated with origin nodes, global convergence of the iterates is not dependent on nondegeneracy or convexity assumptions. Numerical experiments indicate the excellent performance of the method on both degenerate and nondegenerate problems.
A Parallel Network Equilibration Algorithm for a Class of Constrained Matrix Problems
Authors: Nagurney Anna , Eydeland Alexander
Published: October 2008

In this paper we propose a network equilibration algorithm for the solution of a class of constrained matrix problems with transportation-type constraints. The algorithm decomposes the problem into two series of supply and demand network equilibrium problems with special structure which can then be solved exactly and in parallel. The theoretical results obtained include the proof of convergence, the rate of convergence, and computational complexity analysis, and are obtained by interpreting the algorithm as a dual method. Computational results on datasets illustrate the theory and the efficiency of this approach.
A New Distance Function for Modeling Travel Distances in a Transportation Network
Authors: Brimberg Jack , Love Robert F.
Published: October 2008

Continuous location models generally use the Euclidean or rectangular norm to approximate travel in a transportation network. This paper considers a new and more accurate distance measure, termed the weighted one-two norm, which is a positive linear combination of the preceding norms. A directional bias function is introduced to show the equivalence of this distance measure to the well known lp norm. We then formulate a simple linear regression model to fit the parameters of our distance function to a given data set. Some novel applications based on standard statistical tests are derived which provide practical insights into the nature of networks with rectangular bias. The results are readily extended to other types of networks.
Bibliographic Section
Authors: Galvão Roberto Diéguez , Govind Shekhar
Published: October 2008

Discrete Location Theory, Pitu B. Mirchandani and Richard L. Francis (eds.), John Wiley & Sons, New York, 1990—reviewed by Roberto Diéguez Galvão.

Urban Port and Harbor Management, Marc J. Hershman (ed.), Taylor and Francis, New York, 1988—reviewed by Shekhar Govind.
A Heuristic for the Periodic Vehicle Routing Problem
Authors: Gaudioso M. , Paletta G.
Published: October 2008

The paper describes a model for the optimal management of periodic deliveries of a given commodity. The goal is to schedule the deliveries according to feasible combinations of delivery days and to determine the scheduling and routing policies of the vehicles in order to minimize over the planning horizon the maximum number of vehicles simultaneously employed, i.e., the fleet size. Heuristic algorithms are proposed and computational experience is reported.
Optimal Location of Discretionary Service Facilities
Authors: Berman Oded , Larson Richard C. , Fouska Nikoletta
Published: October 2008

Automatic teller machines and gasoline service stations are two examples of a growing number of “discretionary service facilities.” In consuming service from these facilities, a significant fraction of customers do so on an otherwise preplanned trip (e.g., on the daily commute to and from work). A system planner, in determining the best locations of such facilities, is more concerned with placing the facilities along paths of customer flow rather than, say, near the center of a cluster of residences or work places. We formally model this problem and present a method for determining the optimal locations of m discretionary service facilities so as to intercept the maximum possible potential customer flow. We also show how to determine the minimal number of facilities required to intercept a prespecified fraction of total customer flow. Computational results are included.
A Method for the Route-Choice Problem in Public Transport Systems
Authors: Jansson Kjell , Ridderstolpe Bosse
Published: October 2008

Passengers in an urban transport system may often be in a position to choose among a set of parallel routes in order to reach their destinations. Their decisions depend in general on many variables, e.g., the in-vehicle travel times, walk time, transfer time, number of transfers, fares, the headways and the irregularity of the routes. Traditional methods used in urban transport planning do not solve the route-choice problem satisfactorily when passengers may choose between modes with differences in speed or fare structures, e.g., tram and bus. The purpose of this paper is to present a method for calculating the passenger waiting times and distribution for the route-choice problem more realistically than existing methods. An implementation of the new method can be found in the new VIPS II urban transport planning system. Large scale testing carried out by the Stockholm Transport Development Department has produced better results than with methods used previously.
Selected Abstracts for the 1990–1991 Transportation Science Section Dissertation Prize Competition
Authors: Laporte Gilbert
Published: October 2008

Fourteen dissertations were submitted to the 1990–1991 Transportation Science Section dissertation prize competition. The first prize was awarded by Dr. Linos F. Frantzeskakis for “Dynamic Networks with Random Arc Capacities, with Application to the Stochastic Dynamic Vehicle Allocation Problem.” Three honorable mentions were also awarded. The recipients are listed in alphabetical order: Dr. Saad A. H. Al-Gadhi for “Characterization of Crowd Behavior and Movement,” Dr. Rina Schneur for “Scaling Algorithms for Multicommodity Flow Problems and Network Flow Problems with Side Constraints,” and Dr. Garrett van Ryzin for “Stochastic and Dynamic Vehicle Routing in Euclidean Service Regions.” The abstracts of all 14 theses submitted are reproduced.