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This paper presents a method for developing efficient timetables for the operation of fixed schedule common-carrier passenger transportation systems. The ability to compute such timetables is needed in the consideration of planning alternatives for future transportation systems and/or the efficient operation of existing systems. Here, time- table optimization is accomplished by maximizing an objective function consisting of three basic components: operating costs, revenues, and traveler benefits. Traveler benefits are computed using a consumer preference model that specifies a traveler's willingness to pay for alternative trips, based on the scheduling of those trips. The optimization is based on successive iterations of a dynamic programming algorithm that develops timetables for each vehicle in the system. Solutions are termed optimal to within a 'first-order passenger exchange! Examples are presented to illustrate the utilization of the methodology for computing information relevant to the development of system operating policies and to the consideration of planning alternatives. [ABSTRACT FROM AUTHOR]

Before we can construct models for multilane traffic flow, we must be able to describe single-lane traffic. This paper considers some of these methods of description including the use of headway and counting distributions. Another method of describing point processes is by means of product densities. These are essentially joint probabilities of two or more vehicles passing a point at different specified times. Product densities have been used in many fields including particle physics, ecology, and road traffic. The idea of using product densities is simple and attractive, but they do have two major disadvantages: (i) except in simple cases, headway distributions are very difficult to derive from product densities, and (ii) product density estimates for different time lags are cor- related, so that tests of hypotheses are not easy to perform. An alternative to product densities is proposed. For want of a better name these are called termination rates. The termination rate after lag τ is the probability of a vehicle passing a point in a small interval of time, divided by the length of the small interval and conditional upon the last vehicle having passed a time τ previously. These are very similar to mortality rates for humans or scrap page rates for commodities with limited life-times. The interrelations between these statistics are quoted but not derived. Various sets of data are used to illustrate the less common statistics. Some analysis is given of a sample of data from the Congress (now Eisenhower) Expressway in Chicago. Variance to mean ratios are used to show that there is a strong correlation between lanes even though the autocorrelations of headways within lanes are very small. Bivariate termination rates have been estimated for each lane. Given a vehicle in one lane, it was found that the expected number of vehicles in a neighboring lane within 2 or 3 sec was enhanced by about 10-15 percent. [ABSTRACT FROM AUTHOR]

The trip distribution model formulated in this paper uses the basic concepts and notation of utility theory. Each trip origin is considered to rate the trip destinations available in order of perference, and each trip destination is considered to rate the trip origins, it is shown that in pairing trip origins with trip destinations in the distribution process, a `stability' condition should be satisfied, and that two particular stable trip distributions, termed `origin-optimal' and `destination-optimal,' are of particular interest. Conditions under which `like' trip origins and `like' trip destinations may be grouped together are then discussed. Finally the model is illustrated using trip data for the small city of Launceston, Tasmania. [ABSTRACT FROM AUTHOR]

The problem treated is that of locating in centers (processing facilities) in a network, so as to minimize the total transportation cost associated with their use. On the assumption that all movements occur between a vertex and a center nearest it, HAKIMI has shown that only vertex locations for the centers need be considered. The present paper shows that this conclusion remains valid under alternative assumptions more appropriate for some applications. [ABSTRACT FROM AUTHOR]

Satisfactory solutions to congestion within and at the access routes of an airport may require data beyond the response to standard origin- destination questions and for all subgroups of airport users. An airport is considered as a closed system generating vehicle and person trips sampled within randomly or systematically selected observation time periods. Sampling at airport egress points may be most effective, but least feasible administratively. An alternative presented in this paper consists of developing a model for estimating the hourly volume of vehicle and person trips from machines counts at egress points and surveying four strata of airport users for collecting additional data with estimation based on post-stratification. [ABSTRACT FROM AUTHOR]

In this paper a scientific method for the construction of timetables for a suburban railway line without branches is developed. It is shown that such timetables are largely determined by stop-schedules. Two criteria for stop-schedules have been considered: the number of inter- mediate passenger stops and the number of carriage miles. A mathematical formulation is presented and it is shown that the problems of finding optimal stop-schedules can be solved with dynamic programming. Zone-stop-schedules, a type of stop-schedule with several operational advantages, have received special attention. [ABSTRACT FROM AUTHOR]

Investigations of motorist delays at the intersection of a major and minor road have involved variations of one or the other of two merging strategies: (i) MILLER'S[8] model that assumes that a minor-road motorist makes consecutive decisions consistently, and (ii) that of WEISS AND MARADUDIN[7] that assumptions that a different, independent decision is made for each headway. In this paper we show that results for both models may be obtained easily, using the results of queuing theory, if certain reasonable assumptions are made. Simple expressions for the Laplace-Stieltjes transforms and means of the delays are derived in the case of independent major-road headways with a common, general distribution. For exponential headways, a numerical study shows the mean Miller delay to increase with the variation in the merge times, while the mean Weiss-Maradudin delay decreases. To illustrate the application of the expressions obtained, we investigate the reduction in the delay achieved by inserting a traffic island between two streams of major-road traffic. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to estimate cost functions for the U.S. passenger airline industry in order to determine the sources of recent observed productivity, increases. A cost function is derived from the Cobb-Douglas production function, and the parameters of that reduced form equation are estimated. Special attention is given to effect of technology on costs. In general, it was found that there seem to be no scale economies present in the production of available seat miles, but that the level of technology has a substantial impact on cost and productivity. [ABSTRACT FROM AUTHOR]

Two transportation systems, following the same alignment, serve an area from which population commutes to a central point. One system has a constant speed and can be taken at any point along the line; the other has a discrete movement and can be boarded at stations only. The study analyzes the optimal station locations of the latter system for which its patronage will be maximum, assuming that passengers select systems on the basis of shorter travel time. The optimal solution, derived analytically and shown graphically on a time-distance diagram, indicates that the interstation spacings for this objective should be increasing at a decreasing rate in the direction of cumulation. Compared with the optimal interstation spacings for minimum total passenger travel time, given in a recent paper by VUCHIC AND NEWELL, this solution has a greater density of stations and, naturally, larger travel times. Sensitivity of the two solutions to various parameters is examined. Several problems to which this model would be applicable are shown and the model's realistic validity is discussed. From the optimal solution and numerical examples, several conclusions are drawn that are directly relevant to the planning of station locations for discrete public transportation systems. [ABSTRACT FROM AUTHOR]

Hillier has described a method of selecting offsets to minimize delay in certain networks controlled by fixed-time signals. In this paper an attempt is made to extend the method by relaxing somewhat the restriction on the form of the network. The problem is expressed in terms of the theory of graphs, and an iterative process is developed for finding a set of offsets that minimizes delay over the whole network. At each stage, the part of the network already covered is extended by adding one or more links, and for the method to be viable these links must be chosen so that a certain set of intersections remains small. A method of selection of links that minimizes this set of intersections at each stage is developed. The selection of links and calculation of offsets have been programmed in Fortran. Having found one delay-minimizing set of offsets, some others that give the same total delay can be found if they exist. [ABSTRACT FROM AUTHOR]

When a traveler, or other user of a congested system, wishes to be reasonably sure of reaching a destination, or finishing a task, on time he must start early enough to compensate for random delays. This paper investigates the headstart decision policy arising if costs are attached both to lateness and to an otherwise undesirable early departure. The model encompasses a case in which the probability distribution of congestion delays is unknown, and must be inferred from previous experience. [ABSTRACT FROM AUTHOR]

This paper is concerned with the development of a model for planning shipping prices over various routes of a transportation network. It is assumed that over each route a 'railroad' (or other transport firm) competes directly with one other shipping firm (e.g., another railroad, a trucker) for the volume of business that is to be shipped over the route. We allow the possibility that the railroad's competition will come from different firms over different routes. The model we consider is a multiroute problem that involves both institutional and physical operating constraints. Each firm's demand depends linearly upon its own and its opponent's price. Since each competing firm sets its price policy independently and before the variable demand is known, some of these constraints cannot be guaranteed to hold with certainty. Thus they are best expressed as chance constraints. The objective of the 'railroad' is to maximize its profit subject to the constraints of the model. The solution of the model synthesizes a pricing policy for the 'railroad'; we also indicate how variations of the model can be employed in a sensitivity analysis of the suggested policy and discuss the relation between our model and other notions in game theory and chance-constrained games. An example is outlined, and the implications for a welfare-economic pricing policy considered. [ABSTRACT FROM AUTHOR]

When an interstate highway is completed between two cities less than 200 miles apart, some people find it more convenient to switch from air travel between the two cities to automobile or bus travel. This paper employs a multiple regression model to quantitively examine this effect of interstate highway construction on short-haul air market. Several techniques are used to isolate the impact of changing highway quality on the short-haul air market from a myriad of other influencing factors. The city-pairs chosen for the regression sample are all between 105 and 185 miles apart so that the distance variable is constrained. An 'airport use' variable is introduced to reflect changing environmental demand determinants such as income and population. The regression is run in first difference form, which eliminates multicollinearities as well as the influence of static factors. Finally, quarterly data is used rather than yearly data to provide more degrees of freedom, and quarters are compared with the same quarters in an earlier year to eliminate the effect of seasonal variations. The coefficients of the resulting regression indicate two important conclusions. First, short-haul air markets are growing only about half as fast as the air market as a whole. Second, a significant number of travelers do switch from airplane travel to automobile travel when an interstate highway is made available for a one hundred to two hundred mile trip. [ABSTRACT FROM AUTHOR]

The impact of new and improved transportation facilities on urban travel behavior is a topic seldom addressed in transportation-research literature. The paper presents a method for classifying travel behavior of urban residents and suggests a procedure for quantitatively estimating diverted traffic. An application of the method is made to a limited sample of Chicago's residents. Seven groups of residents with similar travel patterns were identified and the impact of a new expressway on each of the seven groups was estimated. The study suggests a reorientation of research activities: in addition to the analyses of aggregate traffic data a greater attention should be directed toward detailed inquiries about the travel patterns of urban residents and the spatial structure of commercial traffic. [ABSTRACT FROM AUTHOR]

The paper discusses the computer construction of the lists of weeks of work that form the basis of the rotating roster for crews operating buses for a transit system. There are two construction phases; the first consists of making a day-off pattern and the second consists of placing daily shifts in the lists under the constraint of the day-off pattern. Techniques used to attain objectives include integer linear programming and optimal assignment. [ABSTRACT FROM AUTHOR]

The networks considered in this paper consist of ring roads and equiangle spirals rotating in both directions. Journey lengths and numbers of crossings of paths are found for a circular city with uniformly and independently distributed origins and destinations of trips. The 30° spiral-and-ring network gives an average journey length 18 per cent less than a 90°-grid and 5 per cent less than a ring-and- radial network for this city. The minimum number of crossings of paths is about 14 per cent less than would be obtained if drivers could travel in straight lines between origin and destination. This minimum is obtained with a 70° spiral-and-ring network. [ABSTRACT FROM AUTHOR]

There are frequently several different ways in which passengers may fly from any one point to any other in an airline network. Passengers may choose a nonstop flight, a flight using the most desirable type of aircraft, a flight departing or arriving at the most convenient time, and so on. It is therefore necessary for an airline to plan many months ahead to obtain a flight schedule that will best answer the needs and desires of the traveling public. The Passenger Allocation Model has been designed and developed to assist in this planning process. It allocates a forecast volume of passengers, traveling from any point in the system to any other point, to the various flight paths offered by a proposed schedule. Decision rules are used that quantify the effects of such factors as the frequency of all flights between the two points, the times of arrival and departure of each flight, the types of aircraft to be used, the types of flights (direct or connection) and the number of seats available. This paper describes the general structure of the model. [ABSTRACT FROM AUTHOR]

Traffic flow past a point varies with time owing partly to statistical fluctuations and partly to a variation in the mean. Highway traffic surveys frequently include as a measure of this variation, peak short- time flows (1-, 5-, or 15-min flows) during a longer time (15, 30, or 60 mm). Near the peak of the rush hour, the expected flow should be nearly stationary and variation in short-time flows should be due mostly to statistical fluctuations. This paper describes methods for estimation of these peak flows under the assumption that the short- time flows are approximately a stationary Gaussian process with a variance-to-mean ratio of about 1. The theory suggests that one can predict the distribution of peak short-time flows (5-mm flows, for example) from the peak long-time flows (15 or 30 mm flows). Experimental data seem to confirm this. The implication is that these short-time peaks have no obvious relation to highway capacity beyond that already inferred from the longer-time flows. [ABSTRACT FROM AUTHOR]

Recent developments in aircraft technology will create greater airlift capabilities at lower costs. How will this increased capability be effectively utilized by the Department of Defense? Time-series extrapolations of air-cargo demand have been made in the past for the civil sector of our economy and similar projections have been proposed for military airlift planning. These proved less than successful when compared with actual tonnages generated. This paper will explore a different methodology for predicting airlift demand in the military establishment. Basic data, consisting of approximately 3.8 million commodities and millions of shipments recorded on magnetic automatic data processing tapes, are obtained from all DOD supply management activities. Two information files are established. One is a catalogue file reflecting the physical characteristics (weight, cube, price, etc.) of the commodities that influence total distribution costs of delivering the items to overseas destinations. The second is a demandfile containing the actual volume and traffic flow of the commodities. From these files, total distribution costs for air and surface movement are computed by a mathematical model for each commodity to determine the break-even air rate. The economically air-eligible commodities are then correlated with the volume and traffic flow to determine the elasticity of demand at various air ton-mile rates. Based on known operating costs of new aircraft, logical requirements for airlift can be established. At the same time, criteria for selecting air-eligible commodities are based on economic considerations, thus producing the least-cost method of supplying overseas activities. [ABSTRACT FROM AUTHOR]

In this paper the authors find the optimal allocation of servicing periods to a facility servicing N incoming traffic streams. In our model it is assumed that stream flows are deterministic, that there is a fixed amount of lime lost, τi , when the server switches attention from the ith to the i + 1st stream and that the objective is to minimize time average delay. [ABSTRACT FROM AUTHOR]

A simple mathematical model of a satellite town is presented in this paper. It is shown that the model contains the basic features of a satellite New Town as well as of a satellite Residential Town. The characteristics of commuter travel in a satellite Residential Town are investigated, and the size of the Central Area and of the satellite town, the distance traveled per unit area, and the average distance traveled, are evaluated. For an initial sample set of data, numerical results are presented and discussed. [ABSTRACT FROM AUTHOR]

In the paper "Sources of Productivity Increases in the U.S. Passenger Airline Industry," a log-linear cross-section function was estimated with several independent variables of the "dummy" or "shift" form. In this type of estimating procedure, the dummy variable is interpreted as a shift in the intercept due to some discrete event that is thought to influence the dependent variable. However, the intercept of the estimated linear transformed equation is a multiplicative factor in the equation before transformation. The nontransformed equation, of course, has no intercept. For this reason, the impact of technical change on cost cannot be determined from the equation directly. Using some values for each of the continuous independent variables, use the equation to calculate cost. In this case the mean values of the logarithm were used. If the value of each of the dummy variables is zero, then this calculated cost is interpreted as the expected annual cost of running a propeller driven plane for the sample geometric seat miles, fuel-cost, etc. Replicate this procedure with the addition of a value of unity for the first dummy variable. This is interpreted as the expected annual cost of running a turboprop plane for the sample geometric mean values of the continuous independent variables.

This article presents information for contributors to the journal "Transportation Science." Manuscripts for publication and Letters to the Editor should be submitted to the Editor either directly or to one of the Associate Editors. The submission of a manuscript is taken to be the author's representation that the manuscript has not been published or accepted for publication in books or recognized journals and is not currently under consideration by another journal. Manuscripts must be double-spaced throughout with the original in typewritten or equally legible form. Complete and legible duplicate and triplicate copies are necessary to accelerate the process of refereeing and are strongly recommended. The style of this journal should be followed in the preparation of manuscripts. Each paper must be accompanied by an abstract of about 100 to 200 words. The abstract should be adequate as an index and should summarize the principal results and conclusions. Authors should strive for conciseness and clarity. References to related previous work should be reasonably complete, consecutively numbered, and grouped at the end of the paper.

This article presents information regarding the International Conference on "High Speed Ground Transportation," which is to be held on the campus of Arizona State University from January 7-10, 1975. Papers are requested on both the state-of-the-art and current research in all facets of high speed ground transportation. Fields to be emphasized include: vehicle and guideway; structures propulsion; vehicle and guideway; dynamics; communications and controls; systems optimization; noise and air pollution; regional land planning, new cities; airport access; cargo movement; finance; safety; social and legal factors. The abstract deadline is October 15, 1973, with prospective authors to be notified by November 15, 1973. Manuscripts are requested by April 15, 1974. The papers presented at the conference will be published in the "High Speed Ground Transportation Journal." The abstract limit is 500 words.

There seem to be errors of two types in the paper "Sources of Productivity Increases in the U.S. Passenger Airline Industry." The errors of the first type are numerical. Table I gives the estimate 0.0311 for the parameter "h," associated with the common logarithm of the time shift variable Y, and -0.0511 for the parameter "g." The second type of error is much more fundamental. Not only is the assumption that a = 1 wrong in principle, but it may have influenced the major conclusion of the paper, which concerns economies of scale. Only by a recalculation, using the same data in the same model without demanding that a = 1, can one confirm or deny this surmise, but the paper's numerical results already suggest the existence of diseconomies of scale; that suggestion would be strengthened, and perhaps made statistically significant.

In his paper, PEARCE presents a method for determining the stationary probabilities of a G/Mt/1 system, the service mechanism being such that it operates regardless of whether or not customers are present. This note is an attempt to correct his results. [ABSTRACT FROM AUTHOR]

The article presents information for authors who want their research work to be published in the journal "Transportation Science." The submission of a manuscript is taken to be the author's representation that the manuscript has not been published or accepted for publication in books or recognized journals and is not currently under consideration by another journal. Manuscripts for publication and Letters to the Editor should be submitted to the Editor either directly or to one of the Associate Editors. Tables may be typed on sheets separated from the text. Manuscripts must be double-spaced throughout with the original in typewritten or equally legible form. Figures are required in a form suitable for photographic reproduction. Any one of a number of forms will be acceptable, e.g., original black ink drawings, or high-quality glossy prints. In mathematical expressions, authors are requested in general to minimize unusual or expensive typographical requirements. Authors should strive for conciseness and clarity. References to related previous work should be reasonably complete, consecutively numbered, and grouped at the end of the paper.

The article presents information related to the deadline for submission and format of the manuscripts and letters to the editor to be published in the forthcoming issue of the journal, Transportation Science. Manuscripts must be double-spaced throughout with the original in typewritten or equally legible form. The style of this journal should be followed in the reparation of manuscripts. Tables may be typed on sheets separated from the text. In mathematical expressions, authors are requested in general to minimize unusual or expensive typographical requirements. Each paper must be accompanied by an abstract of about 100 to 200 words. The abstract should be adequate as an index and should summarize the principal results and conclusions.

Manuscripts for publication and letters to the editor should be submitted to the editor either directly or to one of the associate editors of the journal "Transportation Science." The submission of a manuscript is taken to be the author's representation that the manuscript has not been published or accepted for publication in books or recognized journals and is not currently under consideration by another journal. Manuscripts must be double-spaced throughout with the original in typewritten or equally legible form. Figures are required in a form suitable for photographic reproduction. Any one of a number of forms will be acceptable, e.g., original black ink drawings, or high-quality glossy prints. Lettering should be uniform in size and style and sufficiently large to be legible after reduction. Authors should strive for conciseness and clarity. References to related previous work should be reasonably complete, consecutively numbered, and grouped at the end of the paper. Manuscripts will be considered for publication in this journal when copy conforming to the above instructions is furnished.

The article presents information about an international conference, Transportation Research Forum and the College of Europe, to be held at the College of Europe, Bruges, Belgium, from June 18-22, 1973. The theme of the conference will be "Current Issues in Multi-Modal Transportation," and will focus primarily on matters of inter-modal and international significance. The issues to be discussed will span all modes of transportation and their inter-modal relationships, and will concern both passenger and freight movements. The issues will reflect the perspectives of the public and of the private sectors, and will concern research, policy and planning, as well as operations. Descriptive outlines of proposed papers, in English (300-400 words), should be submitted before December 1, 1972 to: Professor Marvin L. Manheim, Room 1-138, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States; or Dr. H. Brugmans, Rector, College of Europe, 8000-Bruges, Belgium.

This report describes a method developed for analyzing a large bus transport on a digital computer with a view to improving the utilization of buses and the duty allocation for the crew without making elaborate structural changes in the existing setup. With the a priori statistics concerning the alighting and boarding of passengers at each stage of a route for different times of the day and the a posteriori statistics concerning the waiting time of the passengers at various stages of the route as the information supplied by the transport organization, a computer program has been developed to realize time-tables and bus schedules that can optimize the fixed plus variable cost of operation subject to the requirements and constraints imposed on the optimization procedure by the passengers, the crew, and the management. [ABSTRACT FROM AUTHOR]

Fluid and diffusion queuing approximations are used to analyze the behavior of vehicle-actuated signals at the intersection of two one-way streets at which there is no turning traffic. The arriving traffic is assumed to be a stationary stochastic process with a flow rate just slightly below that which saturates the intersection. Certain qualitative properties of the queues suggests that to minimize delay the signal should (in most cases) switch as soon as the queue vanishes, defined roughly as the time when the expected flow rate across the intersection drops below the discharge rate of a queue. The mean and variance of the cycle time and the mean delay are evaluated for this strategy. The average delay per car is shown to be less than for a fixed-cycle signal by about a factor of 3. The distribution of cycle time is shown to have approximately a Γ distribution. [ABSTRACT FROM AUTHOR]