bluuebunny/crossref_metadata_2025 huggingface dataset:
Perceptual Thresholds in Car-Following—A Comparison of Recent Measurements with Earlier Results
Authors: Evans Leonard , Rothery Richard
Published: October 2008

The authors have previously conducted a field experiment to investigate the sensitivity of subjects to the sign of relative motion when following a vehicle. They interpreted their results in terms of responses to analytical functions of relative speed divided by spacing, or spacing change divided by spacing. In the present paper the remits of a number of other field, simulator, and laboratory experiments to investigate sensitivity to relative motion reported in the literature are examined in the light of these analytical response functions. It is shown that this approach leads to a relatively consistent interpretation of most of the available data, and that, when appropriately interpreted, there is greater agreement between many of the experimental results than had hitherto been noted.
The “Hub” and “Wheel” Scheduling Problems
Authors: Arisawa Sanji , Elmaghraby Salah E.
Published: October 2008

The problem is that of scheduling truck movement (loaded and empty) between a central depot (the hub) and a number of outlying cities. Current demand is known deterministically, but future demand is uncertain. The myopic case treats two periods only: the current period and one future period. The objective is to minimize the expected total operating penalty, consisting of the costs of moving empties and the costs of delaying shipments. In two special cases the procedures of solution reduce to simple marginal analysis that has been previously solved by Minas and Mitten. In the general case, a network flow model is proposed that is easily solved.
A Traffic Equilibrium Model of Travel by Car and Public Transit Modes
Authors: Florian Michael
Published: October 2008

We develop an equilibrium model of travel by private car and one or more public transit modes. The salient features of the model are the clear distinction between the flow of vehicles and flow of transit passengers and the means of modeling the interaction that occurs between private cars and public transit vehicles that use the same road links of the network. Two classes of model structures for representing the demand for each mode of travel are analyzed. For one of these classes of models, we show that the equilibrium model framework permits the computation of consistent equilibrium flows. The behavioral assumptions that are imbedded in the model are clearly spelled out. Finally, data requirements and computational aspects are discussed in detail. A variety of applications are outlined.
Traffic Delay at Unsignalized Intersections: Clarification of Some Issues
Authors: Daganzo Carlos F.
Published: October 2008

Investigations in this area have been directed at finding the delay to a motorist who arrives at an intersection and wishes to cross a high-priority traffic stream. In this paper two conceptual errors that have appeared in some past publications are identified and corrected.
Books of Interest
Authors: Zettel Richard M. , Reinke David B.
Published: October 2008

Review of books: (1) Transportation Systems Evaluation, Peter R. Stopher and Arnim H. Meyburg, Lexington Books, Lexington, Mass., 1976, 179 pages, $16.00; (2) Urban Transportation Modelling and Planning, Peter R. Stopher and Arnim H. Meyberg, Lexington Books, Lexington, Mass., 1975, 345 pages, $21.95.
Determining All Nondegenerate Shadow Prices for the Transportation Problem
Authors: Fong C. O. , Srinivasan V.
Published: October 2008

Shadow prices derived from the optimal dual solution of a transportation problem give the rate at which the optimal cost changes when a warehouse capacity or market requirement is changed ceteris paribus. One of the limitations in interpreting shadow prices for managerial use is that they may be degenerate, i.e., their interpretation may be valid only over a zero range of the parameter to be varied. This paper provides an efficient procedure for computing all nondegenerate (or “real”) shadow prices. The method involves breaking the optimal basis tree into subtrees by dropping basic variables which are at their bounds, defining a measure of distance between the subtrees and solving a shortest path problem between all pairs of subtrees.
Modeling the Joint Distribution of Home and Workplace Locations in a City
Authors: Blumenfeld Dennis E.
Published: October 2008

A number of analyses have been made in recent years to fit models to the separate spatial distributions of homes and workplaces over a city. This paper investigates the fit of a spatial model to the joint distribution of homes and workplaces, taking into account that home and workplace locations are interrelated. The model is expressed as a single continuous function of the home and workplace coordinates, and in its simpler form has three parameters, each with a clear physical interpretation. The model is compared with data on desire-line lengths of work-trips in London and Bristol for different modes of transport, and the results show close agreement in most of the cases that are examined. The analyses suggest that for work trips the model can be used as a suitable, approximation to the trip distribution. The model describes the spatial pattern of travel, and provides a direct estimate of the travel demand, without the need for an iterative procedure. Some implications of the model are discussed and it is shown that the model can be expressed as a continuous variable form of the standard gravity model.
Multinomial Probit and Qualitative Choice: A Computationally Efficient Algorithm
Authors: Daganzo Carlos F. , Bouthelier Fernando , Sheffi Yosef
Published: October 2008

Even though multinomial probit models have many attractive theoretical features and have been proposed for diverse choice problems (such as modal split and route choice in the transportation field), they have never been used in practice due to the lack of an adequate numerical technique for their application. The purpose of this paper is to introduce such a technique and to demonstrate the feasibility of forecasting with multinominal probit models. Our limited computational experience with the proposed numerical technique indicates that it is accurate, and can be efficiently applied to large choice problems.
Optimal Parameters for a Coordinated Rail and Bus Transit System
Authors: Wirasinghe S. Chandana , Hurdle Vanolin F. , Newell Gordon F.
Published: October 2008

Trips between a metropolitan region and its central business district (CBD) during peak periods are served by a coordinated rail and bus transit system. Each locality is served only by a direct bus to the CBD or by a feeder bus to a railway station from which train service to the CBD is provided. Optimal transit service characteristics that minimize the sum of the transit operating costs and passenger time costs are determined. To formula’e a mathematical model of the system it is assumed that a radiocentric regional highway network centered at the CBD exists. Railway lines are assumed to be radial. The demand for public transit is assumed to be deterministic and to vary slowly with location. The optimization is accomplished mainly by the use of basic calculus in conjunction with continuum approximations of certain discrete parameters. Approximate, but simple and explicit, formulations for the optimal railway inlerstation spadngs, feeder-bus zone boundary and train headways are determined. The relationship of the interstation spacing at a given location to two local demand parameters, a cumulative demand parameter and to various travel-time and cost parameters is shown clearly. A numerical example is also presented.
On the Kinetic Theory of Traffic Flow in the Case of a Nonnegligible Number of Queueing Vehicles
Authors: Lampis Maria
Published: October 2008

The interaction term of the Prigogine kinetic equation of traffic flow is modified in order to account for the existence of a nonnegligible number of queueing vehicles. The speed distribution of the queues is introduced for this purpose. New equations are obtained for a stationary homogeneous flow. The new model is compared with the Prigogine theory and with available experimental data.
Computational Algorithm for a Fixed Cycle Traffic Signal and New Approximate Expressions for Average Delay
Authors: Ohno Katsuhisa
Published: October 2008

A computational algorithm for several characteristics such as the average delay, the average queue length and the probability of clearing the queue is devised for a fixed cycle traffic signal. The values of the average delay given by several theoretical expressions are compared with the exact values computed by the present algorithm. This comparison suggests new approximate expressions for the average delay. New approximate expressions and existing approximate expressions including Webster's full expression and Newell's expression are compared numerically with exact values of the average delay. It is shown that new approximate expressions give almost exact values of the average delay. In addition it is shown that Newell's expression is the most accurate of the existing approximate expressions.
Optimal Sequences of Fixed Time Signal Plans
Authors: Guberinić S. , Senborn G.
Published: October 2008

Most area traffic control systems use fixed-time signal plans because these strategies are efficient and easy to implement. Fixed-time plans are calculated for a number of characteristic traffic situations and are implemented when such a situation arises. Taking into account the fact that changing from one plan to another causes an increase in delay for the vehicles in the network, in this paper a method for determining optimal sequences of signal plans is developed. The optimal sequence is determined using dynamic programming methods and optimal plans for characteristic situations are calculated using the TRANSYT program. The objective function is the total delay in the network during a chosen period.
An Attempt to Characterize Traffic in Metropolitan Areas
Authors: Chang Man-Feng , Herman Robert
Published: October 2008

An attempt has been made to explore the differences and the similarities in traffic characteristics among various metropolitan areas using a large observational data base. The results show that speed distribution functions, including the percent of time stopped and average speed are traffic attributes that are useful in characterizing traffic on various roadways. In terms of the average speed and the percent of time stopped the character of the traffic in several metropolitan areas has been compared and found to be different, although the levels of acceleration used by drivers are similar. Relations appear to exist between the average speed and a number of other traffic variables, such as acceleration noise, coefficient of variation of speed, and stop time which are independent of the area studied. Therefore, among all the mentioned variables average speed is particularly useful in measuring the “quality” of traffic in different areas on various roadway types. Based on information on average speeds, the extent to which “traffic quality” might affect fuel consumption in different metropolitan areas has been estimated.
Locating an Obnoxious Facility on a Network
Authors: Church Richard L. , Garfinkel Robert S.
Published: October 2008

We deal with the problem of locating a point on a network so as to maximize the sum of its weighted distances to the nodes. It is shown that there is at least one optimal point in a finite set of points which can easily be generated. An algorithm is given for locating an optimal point in this set. When the network is a tree, this set consists of the “dangling” nodes.
Control Strategies for Transport Systems with Nonlinear Waiting Costs
Authors: Barnett Arnold I.
Published: October 2008

The interaction between a transport company and its passengers is modeled as a cooperative game in which the company, subject to an economic constraint, uses the vehicle dispatch strategy under which a time-related cast function for passengers is minimized. A rudimentary transport system is studied in detail, and the joint optimal strategy for passengers and the transport company is obtained.
Automobile Fuel Economy on Fixed Urban Driving Schedules
Authors: Evans Leonard , Herman Robert
Published: October 2008

Various fixed urban driving schedules have been defined to represent the speed-time characteristics of urban traffic. When the fuel economy of a particular vehicle is measured using a fixed urban driving schedule, the result depends on the particular schedule chosen. In the present paper it is shown that the differences in fuel economy measured using different schedules can be satisfactorily explained in terms of a simple model, relating fuel consumption to the average speed of urban traffic, previously derived by driving instrumented vehicles in actual street traffic.
Modelling the Tendency of Buses to Form Pairs
Authors: Chapman R. A. , Michel J. F.
Published: October 2008

The paper describes a simple mathematical model of the behaviour of buses, on a relatively frequent service, after one has arrived at a stop at a time different from that scheduled. The model is similar to that used in some earlier papers on the pairing of buses, but derives a different objective function. Results are presented in terms of parameters relating to the scheduled headway (h) and the size of the initial deviation from it (hd), the usual time spent by a bus at a stop, and the ratio (k) of the passenger arrival rate to the boarding rate. A graphical method was employed to find P, the number of the stop at which the first two buses form a pair. For the typical values of parameters used the relationship P = 1/6dk was deduced which, although no generality is claimed, can be used to set operational limits so that the bunching of buses does not occur. Limitations of the model are discussed.
Book of Interest
Authors: Gosling Geoffrey D.
Published: October 2008

A review and recommendation of the book Airport Systems Planning by Richard de Neufville, MIT Press, Cambridge, Massachusetts, 1976, 232 pp., $14.95.
Optimality Conditions for a Dynamic Traffic Assignment Model
Authors: Merchant Deepak K. , Nemhauser George L.
Published: October 2008

We consider a dynamic traffic assignment model formulated as a nonlinear and noneonvex mathematical program. Necessary optimality conditions require equalization of certain marginal costs for all the paths that are being used, and these optimality conditions are shown to be a generalization of the optimality conditions of a conventional static traffic assignment problem. We also examine the behavior of the dynamic model under static demand conditions and show that in this case our model is a generalized version of a standard static model. Our model suggests a promising refinement of the objective function for the static case.
Book of Interest
Authors: Fiala F.
Published: October 2008

A review and recommendation of the book Tourenplanung-Verfahren zur Einsatzdisposition von Fuhrparks, Fritz Mathäus, S. Toeche-Mittler Verlag, Darmstadt, West Germany, 1978, 244 pp., DM 38.
Some Probability Densities Associated with the Joint Location of Homes and Workplaces in a City
Authors: Khaw Keng Hong , Vaughan Rodney J.
Published: October 2008

In a recent paper, Blumenfeld (Blumenfeld, D. E. 1977. Modeling the joint distribution of home and workplace locations in a city. Trans. Sci. 11 307–337.) outlined the continuous modeling approach to the description of the joint distribution of homes and workplaces in a city. In this note, the circularly symmetric form of the quadrivariate normal model is further analyzed, and distributions of the desire line lengths and other variables are derived.
Some Issues Relating to the Optimal Design of Bus Routes
Authors: Newell G. F.
Published: October 2008

The following is mostly a discussion of some issues relating to the design of minimum cost bus routes serving a multiple origin-multiple destination trip distribution. The main difficulty in determining any “optimal” routing originates from the fact that the objective function (total cost) is a nonconvex function of the assignment; the higher the demand for trips on a route, the better is the service that one can provide. One consequence of this is that a square grid of straight line bus routes is not likely to be an optimal geometry even under highly idealized conditions. “Good” geometries are more likely to focus routes onto a single street and past a common junction.
Car-Following Headways on Freeways Interpreted by the Semi-Poisson Headway Distribution Model
Authors: Wasielewski Paul
Published: October 2008

The goal of this work is to investigate driver car-following patterns on freeways, particularly as a function of traffic flow level, using a headway distribution model. A number of authors have developed “two-component” vehicular headway distribution models that assume vehicles on a road can be divided into two groups according to whether or not they are interacting with the vehicle ahead. A model of this type, the “semi-Poisson” model proposed by Buckley, is applied to a data base consisting of 42,000 observed headways from a single lane of an urban freeway over a range of flow from 900 to 2,000 vehicles per lane per hour. A previously developed computational method allows the distribution of followers headways to be calculated directly from the observed total headway distribution by numerically solving an integral equation without introducing a parametric form for the followers distribution. The resulting followers headway distribution is found to be independent of the flow with a mean of 1.32 s and a standard deviation of 0.52 s. No statistically significant discrepancies are found between the model results and the observed data. The theoretical basis for the semi-Poisson model is discussed and compared with those of other models in order to assess the plausibility of the interpretation with respect to car following.
Routing and Scheduling of School Buses by Computer
Authors: Bodin Lawrence D. , Berman Lon
Published: October 2008

In this paper, a new procedure for the routing and scheduling of school buses is presented. This procedure has been implemented and tested successfully in two school districts. It resulted in about a 20% savings in cost in one of these districts and the transportation of 600 additional students with one extra bus in the second. Also, in this paper, the key aspects of the procedures for the preparation of the data are explained including the ministop concept, a new and innovative method for the coding of the network data. In each section of this paper, the core algorithm is explained, followed by the modifications that were made in attempting to implement the theoretical procedure. In this way, the contract between theory and practice can be shown.
A Method of Estimating the Free Speed Distribution for a Road
Authors: Branston David
Published: October 2008

The distribution of speeds which drivers would adopt if they were not influenced by the presence of other vehicles is an essential input for both simulation studies and theoretical models of traffic movement on a road. A simple procedure for estimating the free speed distribution, which can be used even when interference between vehicles is substantial, is developed. The procedure requires vehicles traveling at speeds less than their free speed to be identified. Criteria for defining such impeded vehicles are described and compared using data from the M4 motorway. Free speed distributions are obtained for each lane and the estimates of mean free speed are compared with those obtained from a linear regression of average speed against flow.
Specification Analysis for Quantal Choice Models
Authors: Tardiff Timothy J.
Published: October 2008

This paper examines problems involved in the specification of the correct set of independent variables in choice models. The analytical approach is similar to Theil's use of auxiliary regressions in the case of standard linear models. The key conclusions are that the inclusion of superfluous independent variables does not affect the consistency of the correct coefficients of the choice model, but exclusion of independent variables can lead to changes in the coefficients and the structure of the choice model. The sources of change are the possible correlations between included and excluded independent variables and the change in the structure of the random error terms in the utility functions. Because of the flexibility of its error structure, particular attention is given to the multinomial probit model. When independent variables are excluded, asymptotic differences among alternative least squares and maximum likelihood estimators arise because of different implicit error structures. The differences among the alternative estimators and the general effects of underspecification are examined empirically with simulated data.
Zone Scheduling of Bus Routes to Improve Service Reliability
Authors: Jordan William C. , Turnquist Mark A.
Published: October 2008

A model of an urban bus route incorporating measures of both reliability and average trip time is developed. The impact of zone scheduling on these measures is determined by selecting optimal zone structures using a dynamic programming model. Application of the model to a specific bus route shows that zone scheduling can simultaneously improve reliability and average trip time while also allowing bus fleet reductions compared to all-local service.
Methods for Combining Modal Split and Equilibrium Assignment Models
Authors: Abdulaal Mustafa , LeBlanc Larry J.
Published: October 2008

Two ways for combining modal split and traffic assignment techniques into simultaneous mode and route choice models are discussed. In one model, users are assumed to choose their routes according to Wardrop's equilibrium principle and their modes according to mode choice functions of the difference in modal disutility. In the other model, a route and mode choice equilibrium in which no user can change his route or mode to lessen his general disutility is assumed. The advantages and disadvantages of each of these combined models are discussed. Efficient solution techniques for the models are presented; preliminary computational testing showed excellent results. Since these techniques require successive solutions of similar traffic assignment problems, they should be applicable to realistically large problems.
A Stochastic Model for the Temporal Distribution of Traffic Demand—The Peak Hour Problem
Authors: Alfa Attahiru Sule , Minh Do Le
Published: October 2008

One of the suggested techniques for reducing peak period traffic congestion is to flex work hours. If one is to predict the effect this work hour change shall have on the congestion, it is essential to understand how the peak traffic demand develops. However, there seem to be no existing theories explaining this process. In this paper, therefore, a mechanism by which commuters select their departure time from home is suggested and, based on this, a method is proposed for predicting the temporal distribution of traffic demand during the peak period. This should lead to the understanding of the effects of flexed work hours on the congestion. The model developed in this paper is based on the assumption that the commuters wish to arrive at work at a particular time without being delayed for too long in the system. A commuter therefore attaches cost to delays and also to early and late arrivals at work. This model proposes an iterative procedure by which to obtain the distribution of a commuter’s departure time from home, assuming that he tries to minimize the total cost.
A Simple Approach to Linear Facility Location
Authors: Morris James G. , Norback John P.
Published: October 2008

A linear facility is to be located to minimize weighted shortest distances from demand points to the facility. This paper reports on a naive but effective approach. The approach is simple to understand and computer implementation is straightforward. A graphical version may also be used. The approach generalizes to models with more elaborate cost structures than simple proportionality to distance. The analysis addresses uniqueness issues and characterizes the line with respect to other notions of best linear fits.
Observed Multilane Speed Distribution and the Kinetic Theory of Vehicular Traffic
Authors: Edie Leslie C. , Herman Robert , Lam Tenny N.
Published: October 2008

Speed data on the multilane roadways of the New Jersey Turnpike have been obtained by means of aerial photography. The characteristics of these observed distributions have been analyzed in terms of the kinetic theory of traffic which involves three processes: “interaction,” “relaxation,” and “adjustment.” Comparison of various aspects of the theory with the data is made on the basis of the moments of the observed speed distributions through a process of calibration in terms of the parameters involved in the three processes mentioned. Using the moment method employed earlier, we report the first successful effort to calibrate all of the parameters in the basic model. Agreement between independent methods of calibration provides an indication of the validity of the kinetic theory of multilane traffic. A discussion is given of three different flow regimes: “individual,” “collective,” and “hydrodynamic” flow as well as of the discontinuity of flow in the concentration range of about 50–70 veh/lane-mile.
Binding Inequalities for Tree Network Location Problems with Distance Constraints
Authors: Tansel Barbaros C. , Francis Richard L. , Lowe Timothy J.
Published: October 2008

In this paper, we consider the problem of finding locations of several new facilities in an imbedded tree network with respect to existing facilities at known locations so as to satisfy distance constraints, which impose upper bounds on distances between pairs of facilities. It is known that the existence of a feasible solution to the distance constraints is related to shortest paths through an auxiliary network. The arc lengths in this auxiliary network are the upper bounds on pairwise facility distances. This relationship takes the form of necessary and sufficient conditions, termed the separation conditions. We relate “tight” separation conditions to the solution of multifacility minimax location problems and efficient solutions to multiobjective multifacility location problems. In addition, we demonstrate how the multiobjective results provide insight into the question of lowest computational order of an algorithm for determining whether or not the distance constraints are consistent.
Optimal Traffic Assignment with Elastic Demands: A Review Part I. Analysis Framework
Authors: Gartner Nathan H.
Published: October 2008

This study reviews, in two parts, the formulation, interpretation, and solution methodology of the traffic assignment problem with elastic demands, originally described by Beckmann, McGuire and Winsten. This paper (Part I) defines the different possible modes of traffic assignment in a network and identifies the economic rationales of the associated extremum formulations. The accompanying paper (Part II) examines algorithmic approaches for calculating the resulting flow patterns. The assignment problem is characterized as an interaction between users and operators of the transportation system, analogous to the interaction between consumers and producers in the marketplace. The notions of “user-optimization” and “system-optimization” thus acquire congruent interpretations, expressed by a systemwide maximization objective.
Optimal Traffic Assignment with Elastic Demands: A Review Part II. Algorithmic Approaches
Authors: Gartner Nathan H.
Published: October 2008

Part I of this study reviewed the formulation of the traffic assignment problem (TAP) in a network and identified its underlying rationale. This part examines algorithmic approaches for calculating the flow patterns resulting from the different modes of assignment. An efficient methodology for solving the elastic-demand TAP is based on remodeling it as an equivalent assignment problem in an expanded network. The variable-demand TAP is then tranformed into a fixed-demand TAP, with a trip table consisting of the potential demands, and can be solved by available fixed-demand assignment algorithms. Three alternative transformations are described.
Estimation of Roadway Traffic Density on Freeways Using Presence Detector Data
Authors: Kurkjian Andrew , Gershwin Stanley B. , Houpt Paul K. , Willsky Alan S. , Chow E. Y. , Greene C. S.
Published: October 2008

Existing methods of estimating section (link) density on freeways from data provided by electronic presence (loop) detectors typically require extensive knowledge or strong assumptions on prevailing flow conditions, such as homogeneity. Consequently, these methods are known to produce poor estimates in inhomogeneous conditions, or when a priori knowledge of traffic conditions is not available. In this paper, a new data processing approach is presented which estimates density well over a wide range of traffic conditions. It does this by detecting spatially inhomogeneous traffic conditions and compensating the density estimation algorithm appropriately. The data processing algorithm is computationally simple, is not flow-level dependent, does not require any a priori knowledge of traffic conditions on the road and is insensitive to the types of uncertainty found in detector data. The algorithm uses both flow and occupancy data from adjacent detector stations to track the density on a link. A scalar Kalman filter formulation is used to provide the desired density estimate. The simplicity of the filter algorithm is achieved by using a scalar Generalized Likelihood Ratio (GLR) event detection algorithm to compensate the filter for spatially inhomogeneous conditions. Performance of the algorithm is demonstrated with a microscopic freeway simulation.
A Successive Linear Optimization Approach to the Dynamic Traffic Assignment Problem
Authors: Ho James K.
Published: October 2008

A dynamic model for the optimal control of traffic flow over a network is considered. The model, which treats congestion explicitly in the flow equations, gives rise to nonlinear, nonconvex mathematical programming problems. It has been shown for a piecewise linear version of this model that a global optimum is contained in the set of optimal solutions of a certain linear program. This paper presents a sufficient condition for optimality which implies that a global optimum can be obtained by successively optimizing at most N + 1 objective functions for the linear program, where N is the number of time periods in the planning horizon. Computational results are reported to indicate the efficiency of this approach.
A Note on the Accuracy of the Continuum Approximation Spatial Aggregation Algorithm of Traffic Assignment
Authors: Sheffi Yosef , Trexler Robert
Published: October 2008

This paper investigates the accuracy of the probit approximation based solution of the spatial aggregation problem of traffic assignment. It tests the normal approximation to uniform intrazonal travel times and the Clark approximation to the solution of the choice probabilities between alternatives characterized by normally distributed travel times. Some guidelines for using the technique are developed.
Optimal Sampling Strategies for Statistical Models with Discrete Dependent Variables
Authors: Daganzo Carlos F.
Published: October 2008

The object of this paper is to improve the cost-effectiveness of data gathering procedures for models with discrete dependent variables. It is assumed throughout the paper that the true value of the parameter vector is approximately known and that, with that information, one must select a statistically optimal number of observations from different population subgroups to refine the accuracy of the estimate. It is shown that the problem can be reduced to a small mathematical program whose objective function can be written after a few preliminary algebraic manipulations. For binary choice models, these preliminary calculations are simple enough to be implementable on (1979) state-of-the-art programmable hand calculators. It is also shown that choice-based and mixed data can be optimally selected in a similar way; in particular, binary choice-based samples drawn from one single population group are so easy to analyze that all calculations can be performed by hand. Multinomial models are less amenable to hand calculations, except, perhaps, trinomial models which require evaluation of a double integral. The technique extends naturally to limited dependent variable regression models.
Poisson Regression Analysis Under Alternate Sampling Strategies
Authors: Lerman Steven R. , Gonzalez Sergio L.
Published: October 2008

Poisson processes where the mean is a function of known exogenous variables and a vector of unknown parameters have been widely studied and used. However, the existing theory of estimation of the parameters has assumed a random sampling process. This paper extends the estimation theory to two other sampling processes: grouped dependent variables and sampling where the likelihood of an observation is proportional to the endogenous variable. The likelihood functions for the former case are proven to be globally concave for three functions of interest. In the latter case (termed proportionate endogenous sampling or PES), the likelihood function appears intractable but an alternate, computationally simple estimator is found. This estimator is computed by subtracting one from each dependent variable in the PES and treating it as though it were randomly drawn. It is consistent and asymptotically normal, though less efficient than the maximum likelihood estimator. Some numerical examples on simulated data are conducted to explore the effects of grouping and proportionate endogenous sampling on the estimated coefficients.
Errata—Zone Scheduling of Bus Routes to Improve Service Reliability
Authors: Jordan William C. , Turnquist Mark A.
Published: October 2008

The following corrections should be made to the above article, which appeared in Transportation Science, 13, No. 3, August, 1979.
A Method for Direct Estimation of Origin/Destination Trip Matrices
Authors: Carey Malachy , Hendrickson Chris , Siddharthan Krishnaswami
Published: October 2008

Estimates of the volume of travel between zones or locations is often a necessary step in transportation studies. This paper suggests a method of estimating origin/destination volumes, using a direct demand function and incomplete, aggregate data. Most attention is devoted to demand functions which are linear in their parameters. With such demand functions, volume estimates are obtained from a quadratic programming problem, which minimizes the sum of squared errors from a direct demand function, subject to constraints derived from observations of some travel volumes. A decomposition algorithm is suggested for solving the programming problem and is proven to converge. The method may also be used in the trip distribution phase of the conventional urban transportation model systems (UTMS).
A Model of Driver Behavior at High Speed Signalized Intersections
Authors: Sheffi Yosef , Mahmassani Hani
Published: October 2008

Driver behavior at high speed signalized intersections is modeled in this paper as a binary decision (stop or go). A driver is assumed to stop if the time to arrive at the stop bar, at the onset of amber, is smaller than some critical time. Assuming that time perception and the critical time are normally distributed among drivers, the model's parameters are estimated using a probit calibration routine. The approach is shown to significantly reduce the sample size needed for estimating dilemma zone boundaries and therefore it represents a significant cost saving. As shown in the paper, the dilemma zone boundaries can be directly estimated (analytically) from the model without using stopping probability curves and the implied prior aggregation by speed. The efficient use of the data is a key to the reduced sample sizes needed for estimating the model.
Testing the Multinomial Logit Model against the Multinomial Probit Model without Estimating the Probit Parameters
Authors: Horowitz Joel
Published: October 2008

The multinomial logit formulation of travel demand models is analytically transparent and computationally tractable, but it is based on relatively restrictive behavioral assumptions. The validity of these assumptions for a given choice situation can be tested empirically by comparing the logit model with a general multinomial probit model. This paper describes a Lagrangian multiplier test that enables the comparison to be carried out without estimating the values of the parameters of a general probit model.
Optimum Location Probabilities in the lp Distance Weber Problem
Authors: Drezner Z. , Wesolowsky G. O.
Published: October 2008

In this paper it is assumed that the weights which summarize cost and volume parameters in the Weber problem are known only probabilistically. In general, the object is to find the probability that the facility will be optimally located at any given point or in any region. We assume that the weights have a truncated (no negative values) multivariate normal distribution with known means, variances and covariances. An efficient computational procedure is given in the p = 1 case (rectangular distances) for finding the desired probabilities approximately. An efficient method is also given for finding the approximate probability that a facility will be optimally located at any given demand point in the general lp case.
Spacing of Bus-Stops for Many to Many Travel Demand
Authors: Wirasinghe S. C. , Ghoneim Nadia S.
Published: October 2008

The optimal spacing of bus-stops along a local bus-route with nonuniform many to many travel demand is determined. Weak assumptions are made regarding the local street network. The daily demand functions are assumed to vary slowly within a spacing. The analysis is based on continuum approximations and methods of calculus. The probability of a null demand for boarding and alighting a given bus at a given bus-stop is exploited to space stops closer than otherwise.
A Mathematical Model of a Nonsignalized Pedestrian Crossing
Authors: Griffiths J. D.
Published: October 2008

A mathematical model is proposed to describe activities at a nonsignalized pedestrian crossing. Starting from a set of simple assumptions, the distributions of times during which a crossing is alternately available to pedestrians and vehicles are given. A batch service queueing analysis is then undertaken, employing the imbedded Markov chain technique, to derive the statistics of the vehicular queueing situation. Such analysis usually leads to rather intractable expressions which require a great deal of further effort before numerical results are obtained, but in the present paper these difficulties are overcome, and an explicit formula is derived for the vehicle mean queue length.
On the Dual of the Linearly Constrained Multifacility Location Problem with Arbitrary Norms
Authors: Juel Henrik , Love Robert F.
Published: October 2008

In this article the dual of the multifacility location problem with arbitrary norms is developed and its uses indicated. The formulation allows any number of linear constraints in the primal on the individual new facility locations. It is shown that the multipliers associated with the linear equations of the dual are the optimal facility locations of the primal.
A Trajectory Approach to the Round-Trip Location Problem
Authors: Drezner Z. , Wesolowsky G. O.
Published: October 2008

This paper treats the round-trip location problem proposed by Chan and Hearn. The object of the problem is to find the facility location that minimizes the maximum weighted round-trip distance between the facility and N pairs of demand points. The algorithm proposed here is based on the numerical solution of differential equations. Unlike the Chan and Hearn algorithm, which is based on linear programming and is applicable only to rectangular distances, this method is equally applicable to Euclidean and general (lp) distances.
Operating Ratio Regulation: Control Theory Approach
Authors: Cherry Russell , Garston Neil
Published: October 2008

This paper investigates the dynamic effects of operating ratio regulation. This form of regulation allows the regulated industry to have preselected markups on noncapital expenditures. In a two-factor model, noncapital expenditures are labor alone. When the firm earns more than a preselected ratio of revenue to labor expenditures, price changes will result and this constitutes the dynamic constraint over time. The industry will maximize the long-run constrained profit function (Hamiltonian) with its control variable, labor. The general conclusion we reach is that regulation of this type causes inefficient production and undercapitalization. Using specific functional forms, we are able to establish the existence and stability conditions for an equilibrium of the constrained profit function and make comparisons for given parameter values, between the dynamic, static and unregulated firms under operating ratio regulation.
Solving Stochastic Transportation-Location Problems by Generalized Benders Decomposition
Authors: França P. M. , Luna H. P. L.
Published: October 2008

The discrete Stochastic Transportation-Location Problem, a mathematical model that captures the impact of uncertainty on location decisions, is a mixture of the classical plant location problem and the stochastic transportation problem. With demand at each destination a random variable, the problem is to minimize the sum of expected holding and shortage costs, (linear) shipping costs, and fixed construction costs. We discuss the use of Generalized Benders Decomposition to solve the resultant mixed-integer nonlinear program; this technique yields (convex) stochastic transportation subprograms, whose optimal multipliers generate constraints (cuts) for a master integer location problem. The selection of optimal multiplier vectors likely to yield rapid convergence is emphasized. Limited computational experience is found to be encouraging.
Design Methodology for Airport Limousine Service
Authors: Banks James , Driscoll Wade , Stanford Robert
Published: October 2008

A methodology for the operational design of an airport limousine service is presented. The design procedure involves optimization of a total cost function (involving operating cost and passenger time) for headway and zone dimensions, given rectangular zones. Effects of using layover buffers to dampen variations in run times are considered. Route-deviation service is compared to taxi-fed, limited-stop service. An extensive sensitivity analysis on the model parameters is included, and an application of the methodology to San Francisco International Airport is briefly described.
Design of Local Bus Service with Demand Equilibration
Authors: Kocur George , Hendrickson Chris
Published: October 2008

Local bus service design options are analyzed in this paper, including route spacing, headway, and fare, both with and without vehicle size constraints. Optimal levels of these variables are obtained analytically for three objective functions, including profit maximization, maximization of a combination of net user benefit and operator profit, and maximization of net user benefit subject to a deficit constraint. The analysis uses an equilibrium framework with transit ridership sensitive to the level of service provided by the bus system. The major results consist of closed-form solutions for the optimal local area operating policies, which are dependent upon local conditions, transit service objectives, and coefficients of the demand and cost functions.
A Model of the Effect of Information Diffusion on Travel
Authors: Lerman Steven R. , Manski Charles F.
Published: October 2008

Existing models of travel demand do not reflect the dynamics of the process by which demand adjusts to changes in the travel environment. One of the main causes of these dynamics is the fact that the entire population is not instantaneously aware of the changes in the transportation system. Rather, some individuals may learn about changes only after receiving a word-of-mouth or media report. This paper explores how this information diffusion process influences travel demand. A general model requiring only data on aggregate demand over time is proposed. This model is consistent with plausible behavior at the level of the individual traveler. The model is appropriate for the case of a once-and-for-all structural change in the transportation system. The econometric problems of estimating the parameters of the model are considered, and some interesting forms for the information diffusion process are derived. An illustrative application to an off-peak free fare experiment in Salt Lake City is described.
Relaxation Algorithms for the General Asymmetric Traffic Equilibrium Problem
Authors: Dafermos Stella
Published: October 2008

In this paper we establish the convergence of two relaxation algorithms designed to solve, respectively, the extended single-mode and the general multimodal network equilibrium problems. Both algorithms are shown to converge linearly; the first under the assumption that the cost functions are not too asymmetric; the second under the assumption that the cost interaction among the different modes is relatively weak.
On the Uniqueness and Globality of Optimal Data Gathering Strategies
Authors: Daganzo Carlos F.
Published: October 2008

It was shown in a previous publication that, in order to minimize the prediction error of a statistical model with a discrete dependent variable, it is possible to design an optimal survey by solving a nonlinear mathematical program with linear constraints. It is shown here that this mathematical program is a convex programming problem and that the gradient and Hessian of the objective function admit a closed form. Consequently, very efficient optimal seeking methods which guarantee a globally optimal sampling strategy can be used. As a byproduct of the analysis a simple test for multicollinearity was also developed.
Vertex Centers of Trees
Authors: Farley Arthur M.
Published: October 2008

A unified theoretical basis for a class of vertex centers of trees is presented. A general algorithm for determining such vertex centers is defined and proved to be correct. A linear (in both time and space) implementation of the algorithm is specified in a FORTRAN-like code. A leaf-determined representation of trees is introduced. This representation makes possible the linear time property of the implementation. Two notions of tree center that fall outside the domain of the algorithm are discussed.
Transit Vehicle Stopping Regimes and Spacings
Authors: Kikuchi Shinya , Vuchic Vukan R.
Published: October 2008

This study analyzes the optimum number of stops and the optimal vehicle stopping policy for operation of a transit route. Two optimality objectives are considered: minimum user travel time and minimum total cost (user cost plus vehicle operating cost). Three types of vehicle stopping schemes are incorporated in the model: all-stop, on-call stopping and demand stopping. These represent most of the existing fixed route transit stopping schemes. This study further identifies factors which influence the optimum number of stops and the stopping scheme. The sensitivities of the optima to the selected factors (passenger volume, headway, vehicle capacity and access speed) are examined. It is seen that the optimum number of stops is a function of the number of passengers for a one-way vehicle trip; for small passenger volume, the optimum number of stops is large; for large passenger volume, the number of stops decreases and approaches a constant value. Accordingly, the optimal stopping scheme changes from demand, to on-call and finally to all-stop operation. This study provides a theoretical basis for the selection for transit stopping policy and the number of stops under different operating conditions.