bluuebunny/crossref_metadata_2025 huggingface dataset:
Equilibrium Flows on Urban Freeways
Authors: Hurdle V. F.
Published: October 2008

The equilibrium between supply and demand for travel on a roadway is reexamined without the usual assumption that the system is in a steady state. The demand for travel is treated as a function not only of the perceived cost of travel, but also of the time of day, with strong morning and evening peaks. In order to model typical urban freeway congestion, it is presumed that the peak demand will be sufficient to bring about capacity flow on some critical section of the roadway. Two different situations are studied, an afternoon case in which the travelers are on their way home from work and a morning case. It is shown that the duration of a trip made at a given time during the peak periods is not ordinarily a function of the flow at that particular time, but of the flows that existed prior to that time. Because of this, the equilibrium flows for the afternoon peak cannot be determined by finding the intersection of predetermined supply and demand functions, but only by solving an integral or differential equation. The results for the morning peak come closer to being a straightforward generalization of the usual steady state analysis.
Efficient Algorithms for Solving Elastic Demand Traffic Assignment Problems and Mode Split-Assignment Problems
Authors: LeBlanc Larry J. , Farhangian Keyvan
Published: October 2008

Different algorithms for solving elastic demand traffic assignment problems and mode split-assignment problems are discussed. We note that there are different ways to implement the Frank-Wolfe technique to solve these problems and give the most efficient implementation. We then discuss Evans' procedure and compare it with the Frank-Wolfe technique. Computational results indicate that the Frank-Wolfe algorithm is unstable for the elastic assignment problem—its rate of convergence is very sensitive to values used for upper bounds on trips, which are purely artificial “tuning parameters.” Evans' algorithm is found to be more robust and to converge consistently faster than the Frank-Wolfe technique for both classes of problems studied.
Existence and Uniqueness Properties of an Asymmetric Two-Mode Equilibrium Model
Authors: Fisk Caroline , Nguyen Sang
Published: October 2008

The two-mode equilibrium model with flow dependent transit costs proposed by Florian is examined to determine sufficient conditions for existence and uniqueness of the equilibrium solution. Some implications of these conditions in implementations of the model are also discussed.
Book of Interest
Authors: Horowitz Joel L.
Published: October 2008

A review and recommendation of the book Multinomial Probit: The Theory of Its Application to Demand Forecasting, by Carlos Daganzo, Academic Press, New York, 1979, xiv + 222 pp., $26.50.
Book of Interest
Authors: Florian Michael
Published: October 2008

A review and recommendation of the book Traffic Flow on Transportation Networks, G. F. Newell, The MIT Press Series in Transportation Studies, 1980, 276 pp.
Errata—Optimal Sampling Strategies for Statistical Models with Discrete Dependent Variables
Authors: Daganzo Carlos F.
Published: October 2008

Corrections to be made to the article “Optimal Sampling Strategies for Statistical Models with Discrete Dependent Variables” by Carlos F. Daganzo, Transportation Science 14, 324–345, 1980.
The Level and Structure of Single Voyage Freight Rates in the Short Run
Authors: Serghiou Serghios S. , Zannetos Zenon S.
Published: October 2008

The oil-tanker markets have been for years a puzzle to economists and practitioners alike. Tinberger (1934), Koopmans (Koopmans, T. 1936. Tanker Freight Rates and Tankship Building. Haarlem, Netherlands.) and Zannetos (Zannetos, Z. S. 1966. The Theory of Oil Tankship Rates: An Economic Analysis of Tankship Operations. M.I.T. Press, Cambridge, Mass.) observed a cyclicality in the level of tanker rates and “feast or famine” patterns which cannot be fully explained by a cyclical demand. Zannetos (Zannetos, Z. S. 1966. The Theory of Oil Tankship Rates: An Economic Analysis of Tankship Operations. M.I.T. Press, Cambridge, Mass.) provided evidence linking these phenomena to price-elastic expectations by those who operate in the tanker markets and to the concomitant lumpiness in investment in new tankers. With the advent of the supertankers, especially the very large crude carrier (VLCC) and the ultra large crude carrier (ULCC), another paradox has been added, that of a structure of spot rates. The purpose of this paper is to shed some light on this last issue. A statistical model is constructed describing spot freight rates in terms of the operating costs of the marginal ship, the size of the various vessels relative to the marginal ship, the proportion of the tanker fleet operating in the spot market and the proportion of the fleet which is laid up for more than 2 months. The model developed is validated by using the empirical data of the entire period from September 1971 to December 1976, and also the stratified data of shorter periods characterized by either abnormally high or abnormally low rates. Based on these results, a measure of the economies of scale for tankers for different sizes is developed, and the proportion of these economies which is enjoyed by the shipowner, under various market conditions is calculated.
Statistical Aspects of Injury Severity Part IV: Matched Data
Authors: Hutchinson T. P.
Published: October 2008

By matched data is meant information about two casualties in the same accident (or in very similar accidents that have been matched from a large data set). The two casualties might differ in, for instance, which vehicle they were in, or whether they were or were not wearing a seat belt. Two strategies for the statistical analysis of such data are described. One explicitly models the probability of each combination of severities of injury. The second concentrates on a parameter describing how different are the severities to the two classes of casualty. Several data sets from two fields of application are presented and analyzed as matched data. The first field is the effect of mass ratio on the severities of injury to drivers of vehicles involved in head-on collisions. The second is the difference in severity between belted and unbelted car occupants. The same methods are applicable, of course, to the analysis of other factors. Finally, as an example of the extensions possible with such models, it is shown how it may be feasible to make a distinction between the effects on injury severity of vehicle design and of impact speed, without actually knowing the impact speeds of the accidents.
A Structured Model for Rail Line Simulation and Optimization
Authors: Petersen E. R. , Taylor A. J.
Published: October 2008

A general purpose model of a railway line is presented. This model is based on an algebraic structure which describes the movement of trains over the line. This structure permits an arbitrary number of different trains with differing speeds and priorities to be dispatched over any line configuration including single or multiple tracks and sidings with restricted switching or cross-overs. Both optimization procedures and simulation models of the line can be implemented using this framework. The problem of line blockage at high traffic intensities is discussed, and conditions are given to ensure this does not occur. Computationally simple feasibility tests are presented together with a behaviorally based dispatching model. The model is implemented as a general purpose discrete event simulation model in which different dispatch goals or criteria can easily be included. Details of a validation example involving very high traffic intensity over a typical Canadian rail line are presented.
Baggage Claim Area Congestion at Airports: An Empirical Model of Mechanized Claim Device Performance
Authors: Ghobrial Atef , Daganzo Carlos F. , Kazimi Tarif
Published: October 2008

Although baggage handling is a major airport expense and congestion of luggage claim areas is quite common, knowledge of how baggage claim devices perform their task under congested conditions is virtually nonexistent. In order to bridge this gap this paper describes a model that, for different demand conditions, can predict the performance of a claim device depending on its characteristics. The demand conditions considered include aircraft size, lag between arrival of passengers and bags, and the fraction of passengers that transfer. The characteristics of the claim device that affect performance are frontage length, cycle time, and maximum throughput. The proposed model can predict the accumulation of passengers around the claim device, the time it takes to handle a planeload, and the average passenger service time as the demand conditions and claim device characteristics change. Although the model is deterministic and makes a number of simplifying assumptions, it is also easy to apply if the arrival pattern of bags and people to the claim area is known. Thus, if predictive and/or normative models for these arrivals become available, fairly simple and realistic procedures to study a number of baggage claim area design and operation issues could be developed around the model. The model, which is based on data gathered at the American Airline, National Airline, and Western Airline terminals at San Francisco International Airport, was able to reproduce the observed light congestion phenomena quite well; especially in the case that consisted of a rather large planeload. Unfortunately, lack of resources prevented us to observe a variety of terminals, including situations with much congestion and many bags per passenger. Because of this, further refinements and/or fine tuning of the formulas is definitely recommended.
A Stochastic Analysis of a Tandem Delay System
Authors: Pearce C. E. M.
Published: October 2008

A basic model is proposed for traffic on a two-way, two-lane road which allows that successive queues of fast vehicles traveling behind slow vehicles in one lane may see the same pattern of overtaking opportunities as the opposing stream moves past. A general process of overtaking in bunches is incorporated in the model. We also allow that queues may coalesce when the finite space between two slow vehicles is full of fast vehicles and subsequently fragment again. Fast vehicles do not necessarily all have the same speed. An expression is derived for the mean speed attainable by fast vehicles and a relation found between flow and concentration of fast vehicles. The basic model can be developed in a variety of ways, which give additional information about the fundamental diagram of traffic. Two special cases are treated.
On Binary Mode Choice/Assignment Models
Authors: Florian Michael , Spiess Heinz
Published: October 2008

We consider the two mode equilibrium road and transit assignment model which incorporates a zonal aggregate mode choice model. We reformulate this special structure network equilibrium model as a variational inequality and demonstrate that the origin to destination demands and travel costs, link flows and link travel costs are unique when appropriate sufficient conditions are satisfied. Then we demonstrate the existence of equivalent optimization formulations of special versions of this problem and study sufficient conditions for the convergence of diagonalization methods that are used to obtain solutions for this model.
Further Aspects of Traffic Arrival Patterns on a Multilane Highway
Authors: Mahalel David , Hakkert A. Shalom
Published: October 2008

The model presented in this study describes the arrival pattern of vehicles on a multilane unidirectional highway. It is based on the assumption that in discrete time intervals, the vehicle arrival patterns can be described as a Markov chain process. The Markov properties conveniently enable the expression of interdependence of vehicle arrivals within and among lanes. From the empirical data collected, it was found that in the fast lane, the arrival process is overdispersed and the tendency for bunching is greater than under Poisson distribution conditions. The arrival process in the slow lane is underdispersed and the vehicles tend to distribute themselves deterministically along the lane. The cross-correlation function between the arrival processes in two adjacent lanes indicates a clear dependence between the two processes. This dependence might limit the number of potential overtakings, increases the friction between lanes and increases the probability for a side collision.
Network Optimization with Continuous Control Parameters
Authors: Marcotte Patrice
Published: October 2008

In this paper we consider two network optimization problems which have the following characteristics: control parameters vary continuously and network users behave according to War-drop's first principle of traffic equilibrium (“user-optimization”). For each problem, we study an exact algorithm based on constraint accumulation and a heuristic algorithm previously proposed in the literature.
Some Consequences of Detailed Junction Modeling in Road Traffic Assignment
Authors: Heydecker Benjamin G.
Published: October 2008

Until recently, analyses of the assignment problem have considered only restricted forms of the functions which relate the costs of travel to volumes of traffic. These analyses are not applicable to networks which include detailed models of either uncontrolled junctions or signal-control policies which react to changes in traffic volumes. Recent assignment procedures are capable of modeling both these kinds of junction interaction, and it is therefore of interest to determine under what conditions the behavior of such procedures is assured. In doing so, use is made of a recently established sufficient condition for good behavior in any network. In broad terms, this condition is that the cost of using a link depends mainly on the flow on that link. The condition is discussed, and a related but weaker condition is shown to be necessary to guarantee good behavior. Analysis of detailed models of priority junctions and roundabouts shows that they give rise to cost functions which just satisfy the necessary condition but fail to satisfy the sufficient one. At signal-controlled junctions, the policy which determines how the signal-settings are calculated influences whether or not these conditions are satisfied: various policies are analyzed, and all but one are shown to lead to a violation of the condition which is necessary for good behavior in any network.
Letter to the Editor—On a paper by C. Hendrickson and G. Kocur entitled “Schedule Delay and Departure Time Decisions in a Deterministic Model”
Authors: Henderson J. Vernon
Published: October 2008

A recent paper in this journal by Hendrickson and Kocur (Hendrickson, C., G. Kocur. 1981. Schedule delay and departure time decisions in a deterministic model. Transp. Sci. 15 62–77.) presents a deterministic model of peak period commuting, where departure times, arrival patterns and commuting costs are solved for. It may interest readers to know that this problem in a form almost identical to Hendrickson and Kocur was first solved by Vickrey (Vickrey, W. S. 1969. Congestion theory and transport investment. Am. Econ. Rev. 59 251–261.). Author's Closure follows.
Technical Note—The Denver Free Fare Project as a “Habit Breaker”
Authors: Singell Larry D. , Schifferli Eric
Published: October 2008

The note assesses the impact on bus ridership of the year-long free fare experiment in Denver, Colorado. Data on ridership from February 1977 through October 1980, which includes 1 year before and 1½ after the experiment, are used to estimate the elasticity of ridership when the fare is reduced to zero and when it was reinstated. A cost-benefit analysis argues that the free fare demonstration projects may be justified.
A Linear-Time Algorithm for Maxisum Facility Location on Tree Networks
Authors: Ting S. S.
Published: October 2008

This paper treats a topic in “obnoxious facility location,” namely the problem of locating a single facility in an n-vertex tree network so as to maximize the sum of its weighted distances from the vertices. It is shown that use of a suitable data structure permits a solution algorithm with computational effort O(n), an improvement over the O(n2) required by a previously indicated procedure.
A Second Look at a Problem of Queueing in Lanes
Authors: Henderson W. , Kennington R. W. , Pearce C. E. M.
Published: October 2008

A problem of queueing in lanes treated by Hauer and Templeton is generalized and a solution provided through the use of some combinatorial lemmas. The taxonomy of the Hauer-Templeton model is clarified. Further areas of possible application of the ideas involved are suggested.
A Tactical Planning Model for Rail Freight Transportation
Authors: Crainic Teodor , Ferland Jacques-A. , Rousseau Jean-Marc
Published: October 2008

This paper examines the problems of routing freight traffic, scheduling train services and allocating classification work between yards on a rail network. It describes a general optimization model which takes into account the interactions between these activities and develops global strategies for their management over a medium term planning horizon. A heuristic algorithm developed to solve this nonlinear, mixed-integer multicommodity flow problem is also presented with some computational results based on an example at the Canadian National Railroads.
Passenger Waiting Strategies for Overlapping Bus Routes
Authors: Marguier Philippe H. J. , Ceder Avishai
Published: October 2008

Transit passengers in many urban areas must deal with overlapping bus routes with some routes sharing common stops. Such a passenger can decide either to board an arriving bus or wait for a faster bus—one which will have a shorter in-vehicle travel time. The purpose of this paper is to clarify this route-choice problem using mathematical formulations of passenger waiting times. First an analysis of previous research is carried out based on a field-verified formulation between the variance and the mean of the bus headway and on two headway distribution families. Second, probabilistic mathematical formulations are developed, and an interpretation of the problem is presented. In this second part, overlapping routes are categorized as slow or fast routes, and the proportion of passengers selecting each type of route is derived. The results concerning the route-choice strategies show that an optimal strategy might be to disregard an arriving slow bus. In this case the passenger should wait for a fast bus while disregarding slow buses arriving in the meantime. The results concerning the two route categories show that the intuitive rule in which passengers board the routes in proportion to their frequencies is not a good approximation in all cases, and it can be revised in accordance with this analysis. In addition, this research constructs a framework to consider further aspects of passenger behavior at urban bus stops.
Improved Algorithms for Estimating Choice Probabilities in the Multinomial Probit Model
Authors: Langdon Michael G.
Published: October 2008

One of the problems in the application of multinomial probit models has been the lack of a satisfactory algorithm for estimating choice probabilities. The currently used “Clark” method meets most of the requirements, but is subject to errors which are occasionally unacceptably large. This paper describes a new algorithm which, at the expense of some additional complexity, produces estimates of choice probability which never have large errors. This “separated split” method has many similarities to the Clark method, but employs a different type of recursive structure. Examination of higher moments of intermediate utility distributions has enabled an upper limit to be set on the possible size of error for problems with three choice alternatives. A new “correlated logit” choice model has also been developed, which uses the same recursive structure as the separated split. Multinomial Probit model, but assumes an invariant covariance matrix. It has been found to give a surprisingly good approximation to the exact MNP model for problems with up to six choice alternatives, in many cases producing smaller errors than the Clark method. Under appropriate conditions it condenses to become identical to the well known hierarchical logit model.
The Absolute m-Center Problem on a Directed Network
Authors: Handler Gabriel Y.
Published: October 2008

The absolute m-center problem is a minimax location model particularly suitable for locating emergency facilities on a transportation network. The problem has been well studied for the case of an undirected network. In this note we give a vertex optimality property for the directed version of the problem and show its equivalence to the vertex m-center problem.
Bibliographic Section
Authors: Machemehl Randy , Adler Thomas J. , Rosenbloom Sandra
Published: October 2008

Metropolitan Transportation Planning, John W. Dickey, McGraw-Hill, New York, 1983, xiii + 607 pp—reviewed by Randy Machemehl.

Recent Advances in Travel Demand Analysis, edited by Susan Carpenter and Peter Jones, Gower Publishing, Brookfield, Vt., 1983, xii + 474 pp—reviewed by Thomas J. Adler.

Special Transport Services for Elderly and Disabled People, J. M. Bailey and A. D. Layzell, Oxford Studies in Transport, Gower Publishing, Brookfield, Vt., 1983, $44, 352 pp—reviewed by Sandra Rosenbloom.
Time-Dependent Structural Equations Modeling: A Methodology for Analyzing the Dynamic Attitude-Behavior Relationship
Authors: Lyon Patricia K.
Published: October 2008

The attitude-behavior relationship is expressed as a set of time-dependent structural equations whose endogenous variables are measures of attitudes (continuous) and behavior (binary). The dynamic aspect of the structure is incorporated in three ways: the equations have a lagged endogenous variable (allowing for a lapse of time between cause and effect), the error terms are assumed to be serially correlated (accounting for predispositions which are not captured by the measured variables), and the coefficients are allowed to vary across time (since relationships may differ in importance at various stages in the process). A consistent estimation procedure is described, combining elements of two-stage least squares, generalized least squares, and probit estimation techniques.
Alternating Deadheading in Bus Route Operations
Authors: Furth Peter G.
Published: October 2008

“Alternating deadheading” is an operating strategy for urban bus routes that have a directional imbalance in passenger demand in which some of the vehicles operating on a route deadhead (return empty) in the reverse direction while others return in service. By reducing average cycle time, deadheading can reduce the number of buses needed to serve a route. A formula is developed for the number of buses needed to meet a regular alternating deadheading schedule. Design procedures are then presented for finding the alternating deadheading schedule that will minimize the number of vehicles needed subject to the usual operating constraints, and for minimizing total wait time for a given fleet size. Application to a major local bus route demonstrates the potential of this strategy to reduce fleet size within typical scheduling constraints.
Path Preferences and Optimal Paths in Probabilistic Networks
Authors: Eiger Amir , Mirchandani Pitu B. , Soroush Hossein
Published: October 2008

The classical shortest route problem in networks assumes deterministic link weights, and route evaluation by a utility (or cost) function that is linear over path weights. When the environment is stochastic and the “traveler’s” utility function for travel attributes is nonlinear, we define “optimal paths” that maximize the expected utility. In this setting, the concept of temporary and permanent preferences for route choices is introduced. It is shown that when the utility function is linear or exponential (constant risk averseness), permanent preferences prevail and an efficient Dijkstra-type algorithm can be used.
Note on a Rectilinear Distance Round-Trip Location Problem
Authors: Ichimori Tetsuo , Nishida Toshio
Published: October 2008

This note shows that the rectilinear distance round-trip location problem with N pairs of existing facilities considered by Chan and Hearn can be solved in time 0(N log N).
Bibliographic Section
Authors: Horowitz Abraham D.
Published: October 2008

Car Use: A Social and Economic Study, M. C. Dix, S. M. Carpenter, M. I. Clarke, H. R. T. Pollard and M. B. Spencer, Gower Publishing, Brookfield, Vt., 1983, xxviii + 267 pp—reviewed by Abraham D. Horowitz.
A Graph Partitioning Approach to Airline Crew Scheduling
Authors: Ball Michael , Roberts Anito
Published: October 2008

In this paper, we present a computerized procedure for scheduling airline crews. The procedure performs set partitioning on a graph by decomposing the problem into a series of subproblems which are solved as matching problems. Computational tests of the algorithm reveal consistent performance in producing efficient solutions to the air crew scheduling problem.
Location of Multiple Obnoxious Facilities
Authors: Drezner Zvi , Wesolowsky George O.
Published: October 2008

This problem deals with the location of facilities that are obnoxious in the sense that nearness of the facility to fixed points, which may represent population centers or other installations, is undesirable. Two model formulatons are given. In the first formulation we minimize the maximum weighted distance in the system subject to constraints which require that the distances between the facilities and fixed points must exceed specified values. In the second formulation, the smallest weighted “facility-to-fixed-point” distance in the system must be maximized, given that every fixed point must be within “reach” of the closest facility. Certain useful duality relationships are established between these problems. A one-dimensional problem is solved using an algorithm that incorporates a version of the set covering problem.
Optimal 2-Facility Network Districting in the Presence of Queuing
Authors: Berman Oded , Larson Richard C.
Published: October 2008

This paper considers a districting problem for a demand-responsive service system in which queuing is allowed. Customers, located at the nodes of a transportation network, call in a Poisson manner, asking for on-scene service by a mobile service unit. Two such units service the entire network, with unit i(i = 1, 2) responsible for all nodes Ni in its unique “service territory.” In response to a call from within Nı, unit i, if available, is dispatched immediately to the customer; if the unit is busy with a previous customer, the call is dispatched in a FIFO manner. Each service territory, with its response unit, behaves as an independently operating M/G/1 queuing system. The problem addressed in this paper is determination of the optimal service territories, given fixed home locations for each of the service units, so as to minimize the average response time (queuing delay plus travel time) to a random customer. Exact results are obtained for limiting values of demand rate, and efficient heuristics are presented for arbitrary demand rates.
On Highway Fuel and Time Expenditures
Authors: Trietsch Dan , Handler Gabriel Y.
Published: October 2008

User cost is one of the major considerations when designing a new highway. The vertical alignment of the highway (i.e., the determination of the pavement level along the highway's trajectory), is one of the design oriented factors which affects this cost. In this paper we investigate the influence of the slopes along the highway, which are determined as part of the vertical alignment, on the main parts of the user cost, namely, fuel cost and travel time value. We show that if, and only if, we evaluate each time unit at not less than a value we derive for it by a revealed preference method (from the driver's speed choice), then the sum of the fuel and time costs is a convex function of the slope. We also show that this sum is a convex function of the (traffic) flow. However, if we take the fuel cost alone, we do not get a convex function for either of these cases. For instance, the fuel cost as a function of the slope fails to be convex due to a drop in its derivative at the “critical slope” where the vehicle starts losing speed. Also we note that the same sum is not necessarily a convex function of both variables (slope and flow) together. Finally, we use the convexity of the fuel and time costs to show that the vertical alignment problem is convex too.
Vehicle Scheduling at a Transportation Terminal with Random Delay en Route
Authors: Hall Randolph W.
Published: October 2008

This paper develops and evaluates a simple model for scheduling vehicle arrivals at transportation terminals where vehicles are randomly delayed en route. Equations are developed for the optimal “slack” time (the time between the scheduled arrival for a feeder line and the scheduled departure for a transfer line) when vehicles are delayed according to an exponential probability distribution. These equations only depend on the average vehicle delay and the line headway on the transfer line. The paper shows that coordinating arrivals with departures is most important when the headway is large relative to average vehicle delay.
Optimizing Single Vehicle Many-to-Many Operations with Desired Delivery Times: II. Routing
Authors: Sexton Thomas R. , Bodin Lawrence D.
Published: October 2008

This is the second part of a two-part study treating the single vehicle many-to-many pickup and delivery problem with desired delivery times. Part I detailed the use of the single vehicle algorithm in a multivehicle context, presented a mathematical formulation of the problem, described the application of Benders' decomposition procedure to attack the problem through alternation between a routing, or sequencing, component and a scheduling component, and illustrated a noniterative optimal algorithm for the scheduling subproblem. This part focuses on the routing subproblem, presenting a heuristic algorithm for finding an initial route and a second heuristic algorithm for improving the route sequence. It then integrates the routing and scheduling algorithms, and describes the results of a number of computational experiments on actual data. An example of the complete routing and scheduling algorithm appears as an appendix.
Bibliographic Section
Authors: Daskin Mark S. , Chan Yupo
Published: October 2008

Urban Transportation Networks: Equilibrium Analysis with Mathematical Programming Methods, Yosef Sheffi, Prentice Hall, Englewood Cliffs, N.J., 1985, 399 pp + xvi—reviewed by Mark S. Daskin.

The U.S. Commuter Airline Industry, James F. Molloy, Lexington Books, Lexington, Mass., 1985, 224 pp—reviewed by Yupo Chan.
Simulation of Elevator System for World's Tallest Buildings
Authors: Browne James J. , Kelly James J.
Published: October 2008

The design of the world's two tallest buildings, each 110 stories high, calls for a unique elevator system utilizing 95 local and express passenger elevators per building. Conventional elevator systems' evaluation criteria were supplemented by traffic data and the use of simulation to determine accurately the expected service levels throughout the building. In order to measure the design system's capabilities and to develop and evaluate changes in the elevator specifications, a second-by-second simulation of an entire tower building's elevator operation has been developed, programmed, validated, and applied. Data were collected to develop expected passenger arrival and departure distributions and to determine elevator characteristics—acceleration and deceleration, loading and unloading times. Traffic input data for each of the individual local and express elevators was generated by a series of programs. The computations and logic of the group supervisory control systems for local and express banks are incorporated in simulation programs.
Discrete Programs for Moving Known Cargos from Origins to Destinations on Time at Minimum Bargeline Fleet Cost
Authors: Schwartz N. L.
Published: October 2008

A bargeline which accepts various cargos for timely delivery between pairs of ports in its district must determine the routing and timing of movements of barges and towboats to execute the agreed freight movements at minimum fleet cost. A linear discrete programming model of this optimization problem is developed. The cargo movements to be made and the times needed for transit, loading, and unloading are assumed known. A solution of the model gives the numbers of barges and towboats of each size required to provide the service, with the consequent minimal cost. It also provides a complete schedule for the bargeline, specifying the location and status of the barges, boats, and freight at every time unit of the scheduling period.
A Discrete Markov Model of Vehicular Traffic
Authors: Dunne Michael C. , Rothery Richard W. , Potts Renfrey B.
Published: October 2008

For a number of years the Poisson process has been used as a model to describe the time series of events of vehicles passing a point on a roadway. In its simplest form the Poisson model does not take into account the finite size of the vehicles nor does it properly describe the characteristic bunching of traffic that commonly occurs, for example, on a two-lane road when passing is hindered. To give a more comprehensive description of traffic, various extensions of the Poisson model and a variety of other models have been proposed, with varying success. In this paper a discrete Markov model of traffic is proposed. The model is an extension of the simple binomial model and accounts for the bunching tendency of traffic by assuming correlations between successive vehicles. A description is given of the time-arrival experiments that were carried out to test the model and the statistical analysis of the results of these experiments is discussed. In addition, several theoretical aspects of the model are examined.
A Linear Programming Approach to the Total Movement of a Homogeneous Product
Authors: Conley J. H. , Farnsworth R. S. , Koenigsberg E. , Wiersema U.
Published: October 2008

A linear programming formulation models the movement of a homogeneous product from an overseas origin through United States ports to over 400 inland destinations. The formulation allocates a fleet of over 50 ships of six types to routes between a group of overseas ports and up to seven United States ports. It takes advantage of geographical conditions and the absence of port capacity constraints to reduce the size of the problem by an order of magnitude and to speed computations. The decomposition principle can be applied in either of two ways.
The Oversaturated Signalized Intersection—Some Statistics
Authors: Ancker C. J. , Gafarian A. V. , Gray R. K.
Published: October 2008

This paper describes the examination of an oversaturated signalized intersection with no turning permitted. During the green phase, data on the time between arrivals of successive vehicles at an intersection with no downstream bottleneck have been collected and analyzed. Measurements were made of only the vehicles in queue, i.e., vehicles that were stopped during the red phase and those that were stopped during the green phase because the starting wave had not traveled back far enough. Measurements were made only on weekdays from approximately 7:00 a.m. to 8:45 a.m. in order to restrict the sample, as far as possible, to commuters. It is shown that shifted Erlang density functions fit the data satisfactorily and that all vehicles from the third on may be considered as members of the same population with different means. The mean arrival times decrease from front to rear with all from the seventh on being the same. In addition, our statistical analysis leads us to accept the hypothesis that all interarrival times are independent. Experimental techniques and statistical methods are described. Two uses of these results are (1) to provide information for Monte Carlo simulations of traffic phenomena in which oversaturated situations are being considered, and (2) to develop, as will be done in a subsequent paper, a renewal model that takes account of variability in the empyting process, and that may be used in formulating control policies for the oversaturated situation.
On the Optimal Sampled Data Control of Strings of Vehicles
Authors: Levis Alexander H. , Athans Michael
Published: October 2008

This paper deals with the control of the positions and velocities of high-speed vehicles in a single guideway. It is assumed that each and every vehicle measures its position and velocity every T seconds. The appropriate accelerations or decelerations to be applied to each vehicle are constrained to be constant during the sampling interval. Through the use of a control cost functional, which penalizes the system for any deviations from the desired headway and velocity, the required control accelerations and decelerations are obtained by deriving the system equations in discrete-time and, through the use of available results in the theory of discrete optimal control, the optimal linear time-invariant sampled-data feedback control system is determined. The general results are presented and are used to study the effect of changing the sampling time T upon the control-system performance. Since, in general, the cost of the communication system (in terms of required channel capacity, band-width, etc.) decreases with increasing values of the sampling time, the system designer has the capability of conducting trade-off studies involving the deterioration of the control system performance vs. the decrease in the cost of communication as the sampling time is increased.
Book of Interest
Authors: Miller Alan J.
Published: October 2008

A review and recommendation of the book Traffic Flow Theory & Control, by D. R. Drew, McGraw-Hill Book Company, New York, 1968, 467 pages, $13.75.
Dynamic Model of Weekly Activity Pattern
Authors: Hirsh Moshe , Prashkea Joseph N. , Ben-Akiva Moshe
Published: October 2008

This paper presents a model of weekly activity pattern, based on a theory of individual behavior. The week is divided into time periods, and the following dynamic decision-making process is suggested. At the beginning of the first period, the individual selects his/her activity pattern for the entire week. At the beginning of the second period, the individual updates his/her plans for the remaining periods of the week on the basis of the actual behavior and the additional information that was acquired during the first time periods. In this way, the individual proceeds from period to period and the observed weekly activity pattern is the outcome of successive decisions. Based on utility maximizing principles, a parametric model of this dynamic decision-making process that can be estimated with revealed preferences data is formulated. A version of the model for weekly shopping activity behavior is estimated with survey data from Israel. The model is then applied to predict the effects of shortening the workweek. The empirical results support the dynamic behavior hypothesis and demonstrate the potential biases that may arise from the omission in a travel demand model of the interdependencies among the days of the week.
A Conceptual Framework for Optimal Transportation Systems Planning with Integrated Supply and Demand Models
Authors: Fisk Caroline S.
Published: October 2008

Frameworks for formulating models to determine optimal transportation systems operations or strategic plans are presented which integrate supply and demand characteristics. A conceptual model framework is also given for determining optimal transportation policies or regulations taking into account both supplier and user behavior. New formulations for single supplier problems are derived illustrated by the problem of determining optimal frequencies and fares for a public transit system. A carrier/shipper model in an oligopolistic market situation is presented as an illustration of the multiple carrier problem. Lastly, some algorithms are described which would appear to be tractable for large-scale problems.
Extrapolating Automobile Usage Data to Long Time Periods
Authors: Horowitz Abraham D. , Daganzo Carlos F.
Published: October 2008

This study illustrates a statistical procedure that can be used to estimate the fraction of a given population experiencing a “rare” event during a long time period, given a few days of observation. In an automobile usage context, the rare event could be the occurrence of an automobile occupancy of four or more persons and/or a travel distance of 100 miles or more on any given day. The technique, which can be important for the design of durable goods, is illustrated with four numerical examples.
Some Circumstances in Which Vehicles Will Reach Their Destinations Earlier by Starting Later: Revisited
Authors: Ben-Akiva Moshe , de Palma André
Published: October 2008

Smeed's postulate under which it is possible for a driver to depart later and arrive earlier has been modified to show that under realistic traffic behavior assumptions this phenomenon cannot occur.
The Akaike Likelihood Ratio Index
Authors: Ben-Akiva Moshe , Swait Joffre
Published: October 2008

In 1983, Horowitz proposed the use of an adjusted likelihood ratio index to select between alternative models. We define an alternative index based on the Akaike Information Criterion. The two indices incorporate different degrees-of-freedom corrections to the same measure of goodness-of-fit. The Akaike index favors more parsimonious models. We argue that the Akaike measure is the appropriate criterion for model selection. We utilize Horowitz's results on non-nested hypothesis testing for the new index.
Iterative Algorithms for Bulk Arrival, Bulk Service Queues with Poisson and Non-Poisson Arrivals
Authors: Powell Warren B.
Published: October 2008

Iterative numerical procedures are investigated for the study of queue lengths and waiting times in bulk arrival, bulk service queues. For queues with compound Poisson arrivals, the procedure uses the imbedded Markov chain to study a variety of vehicle dispatching strategies. The technique is easy to implement, numerically stable and, for most problems that arise in transportation, computationally faster than other approaches that have been proposed. For queues with non-Poisson arrivals, an iterative scheme is devised for calculating a discretized form of the waiting time distribution using the concept of unfinished work. Numerical experiments with different discretization strategies indicate that a high level of accuracy can be attained at a very moderate cost.
Constrained Estimation of Direct Demand Functions and Trip Matrices
Authors: Carey Malachy , Revelli Riccardo
Published: October 2008

Estimating the parameters of origin destination (OD) travel demand functions, and hence predicting OD trip volumes, requires data on OD travel demands, but data on travel demands between individual OD pairs are often unavailable or are costly to obtain. However, data on sums (or other linear combinations) of OD travel demands are often more easily or more cheaply available. A recent paper in this journal by M. Carey et al. (Carey, M., C. Hendrickson, K. Siddharthan. 1981. A method for direct estimation of origin/destination trip matrices. Trans. Sci. 15 32–49.) presented a constrained least-square estimation model to take advantage of these kinds of data. The statistical properties of the model were not discussed and were not obvious. The present paper extends the model, solves an equality constrained version, and shows that it has desirable statistical properties, and is a special case of a more general model, which is presented and discussed. Also discussed are observational errors in the constraint equations, nonnegativity and inequality constraints and demand functions which are nonlinear in their parameters.
Service Functions for Urban Freeways—An Empirical Study
Authors: Hurdle Vanolin F. , Solomon Dan Y.
Published: October 2008

A service function, defined as a curve relating travel time to flow, is a standard element of many models of transport system operation. In particular, service functions are frequently used within larger models to describe the way in which the travel time on urban freeway segments changes when the flow increases. In this paper, the shape of such curves for urban freeways is studied by examination of two data sets, one from Ontario and one from California. The most striking feature of the plot of travel time versus flow from each of the data sets is that if the data points are divided into two groups according to whether there was or was not a queue within the section when an observation was made, the two groups of points form separate and distinctly different patterns. The differences are so great that it seems impossible to predict travel time by any model which does not consider the difference between the two conditions. Upon reflection, this conclusion turns out to be anything but surprising and a second conclusion is reached: that if service functions are to be used to describe the operating characteristics of freeway segments which are long enough that the flow within the segment is not everywhere the same, then the flow axis must measure the flow through the bottleneck, not the flow into the freeway segment or any sort of average over the segment. The reason for this is that no consistent relationship between flow and travel time that can be expressed by a simple curve exists for any flow other than that through the bottleneck. For the bottleneck flow, an __-shaped service function seems reasonably descriptive, though of only limited use for predicting travel times.
The Fastest Path through a Network with Random Time-Dependent Travel Times
Authors: Hall Randolph W.
Published: October 2008

This paper introduces the problem of finding the least expected travel time path between two nodes in a network with travel times that are both random and time-dependent (e.g., a truck, rail, air or bus network). It first shows that standard shortest path algorithms (such as the Dijkstra algorithm) do not find the minimum expected travel time path on such a network, then proposes a method which does find the minimum path. Next, this paper shows that the optimal “route choice” is not a simple path but an adaptive decision rule. The best route from any given node to the final destination depends on the arrival time at that node. Because the arrival time is not known before departing the origin, a better route can be selected by deferring the final choice until later nodes are reached. A method for finding the optimal adaptive decision rule is proposed.
Static Blocking at Railyards: Sorting Implications and Track Requirements
Authors: Daganzo Carlos F.
Published: October 2008

In this paper, various strategies for minimizing the amount of switching done at a classification yard are examined. We investigate how the allocation of blocks (the sorting classes recognized at the yard) to classification tracks affects switching work. Given are the sorting classes, as well as the schedule and block makeup of the departing trains. Only static strategies are considered—strategies where every block has been assigned permanently to a classification track. Simple formulas are given for the minimum number of tracks needed to implement a strategy, and for the amount of switching work given a number of tracks. The total track length is also examined. The results are significantly influenced by the number of blocks recognized by the yard; given this number, the results are nearly independent of the train departure schedule, the number of departing trains, and the number of blocks of individual trains. This feature simplifies the study of larger problems (e.g., dynamic blocking strategies) and, most importantly, makes train formation and scheduling an easier job at every yard.