Showing papers on "Headway published in 1982"

Design of Local Bus Service with Demand Equilibration

Abstract: 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.

Transit Vehicle Stopping Regimes and Spacings

Abstract: 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, ...

Radar control for automotive collision mitigation and headway spacing

Abstract: A small solid-state radar combined with a microprocessor makes possible collision-mitigation braking and automatic headway control in cars of the future. The collision-mitigation function involves the application of antiskid brakes under conditions where, based on radar and other sensor inputs, it is certain that a severe collision will take place. The decision-making algorithm is optimized to prevent the unjustified application of the brakes from false alarms. The automatic headway-control function keeps the car at a safe distance with respect to other vehicles on the road ahead. In the absence of other cars the system operates as a conventional cruise control.

Effects of trucks on freeway vehicle headways under off-peak flow conditions

Abstract: The results of a study to determine the effects of the presence of heavy trucks on traffic flow in sections of freeway as an operational measure of total throughput capacity are presented. The variable used to evaluate truck impacts was time headway. Data were collected at two sites on the Houston, Texas, freeway system during off-peak flow conditions. After each observed headway had been classified as to types of vehicles involved in the interaction, various statistical tests were performed to analyze variations in headway due to headway type, lane width, and traffic volume. Headway type (i.e., the types of vehicles involved in the headway interaction) was shown to be the major determinant in length of the headway; those that involved trucks exhibited the greatest magnitude. (Author)

The capacity of a priority intersection - two approaches

Abstract: The paper deals with the prediction of the critical capacity when the minor stream merges or crosses the major stream. The first approach acknowledges the discrete nature of traffic and using the trapezoidal quadrature formula of Dunne and Buckley is shown to give reasonably accurate results despite the simplifying assumptions of gap acceptance and move-up time. The method is able to deal with the complex, possible correlated headway distributions. The second approach, based on the Brennan and Fitzgerald modification of Tanner's formula, approximats to the first formula by assuming the minor-stream traffic is continuous. An underestimation of the critical capacity results. However, this second approach shows the simple relationship between highway transparency and capacity and provides a check on critical capacity determinations using the discrete approach. It also provides a means of obtaining results from a still broader spectrum of headway distributions. (TRRL)

Design Methodology for Airport Limousine Service

Abstract: 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.

Aspects of headway distributions and platooning on major roads

Abstract: Following earlier work on the distribution of headways on trunk roads a study of platooning is presented. Platoons occur randomly, and the distribution of platoon sizes can be closely represented by a modified geometric distribution. A study of autocorrelations between successive headways shows that they are uncorrelated. The distribution of headways in platoons is found to be independent of speed at a given site. The most important result is that almost all followers follow too closely in terms of the highway code advice, and this close following is relatively greater, and consequently more hazardous, at greater speeds. (A) (TRRL)

Innovative transit service planning model that uses a microcomputer

Abstract: Transit service planning is the process of designing appropriate services, including considerations of area coverage, integration with other transit services, and the frequency of service that can be justified economically as well as socially and politically. A simple and usable analytic model to guide management in the search for, and evaluation of, operating strategies that meet local transit service objectives is described. This analysis system is intended primarily for use on single routes or in transit corridors that include a small number of parallel or serial routes. The model system includes as basic components models of supply (system performance), demand (mode and path choice), cost, and evaluation-measure prediction. The supply-and-demand components are linked in an explicit equilibration structure to include the important interactions between transit system performance and passenger volume. Design options that can be explored with the model system include fare and headway changes, scheduling changes such as turn-backs, etc. Two major aspects of this model system are that (a) it is designed to make maximum use of readily available data and (b) it has been implemented on a microcomputer (an Apple III) in order to minimize the investment in computer resources.

Some modified gap acceptance formulae

Abstract: The paper presents a simple function for estimating the absorption capacity of the major road traffic at an uncontrolled intersection. The function takes account of the minimum headway between vehicles in the same lane so that the absorption capacity of a given volume of traffic depends on whether it is concentrated into one lane or spread over a number. The formula also allows adjustments to be made for the presence of queues provided the mean queue lengths are known. The paper compares the results obtained by this model with those produced by Tanner and considers their sensitivities to the underlying assumptions (a). The number of the covering abstract of the conference is TRIS No. 368448. (TRRL)

Bus scheduling manual. traffic checking and schedule preparation

Abstract: This volume is viewed today as a classic reference on manual scheduling practices. It represents a comprehensive effort made over 30 years ago to pull together the state of the practice in this field, and many of those practices still remain valid today. Because of the classic nature of this reference, it is reproduced unchanged from its original edition. Operators today should note that some of the technological references in the original volume are dated, and that the advent of hand calculators, data management systems, and microcomputers may have facilitated some of the processes described. These areas in the report should be fairly easy to recognize. The original report describes in detail an approach for establishing and revising transit schedules and illustrates it with the experiences of a representative transit company. Individual chapters cover passenger load data, running time data, the headway order, compiling the terminal sheet, run cutting, and distribution of schedule information. The document should be especially useful to transit planners and operations managers with responsibility for establishing schedules.

San francisco muni metro: operating issues and strategies

Abstract: The advent of a light rail vehicle system presented the San Francisco Municipal Railway (Muni) with new challenges associated with operating a high-speed subway system. The Metro, as the system is known, is a subway and surface operation on five existing streetcar lines in San Francisco. It carries about 120,000 passengers per day. Muni was able to run extensive tests with its new fleet of LRVs before starting revenue service to check operating characteristics, especially the ability to couple and run a multi-car train. Muni's start-up strategy for a gradual phase-in of LRV service provided opportunities to learn about a far more complex operating environment than traditional streetcar operation. It became apparent in the early operational phases that a traditional schedule approach was unworkable. Before full-scale operation began, it was decided to abandon the usual schedules and use a "dynamic schedule." By headwaying the cars and providing a pool of fallback operators, it was hoped to maximize the use of the LRVs and help meet the ever-increasing demand of Metro passengers. This headway and fallback system was refined to help Metro break the turnaround bottleneck at the Embarcadero Station, which limited the system's capacity. In addition, a central trainmaster at Van Ness Station improved the consistency of service. The headway and fallback system's shortcomings include partially developed crew dispatching and trainmaster procedures and stacking of outbound trains caused by system saturation.

A fault-tolerant/fail-safe command and control system for automated vehicles

Abstract: Redundancy and fault-tolerant computer technology are being applied to the development of a command and control system for automated vehicles. An ultrareliable command and control system is described which meets the availability and safety requirements for an automated transit system. The technology presented is applicable to a wide variety of computer-based controls where safety is involved or where interruption of the control process cannot be tolerated. High-performance computer-based controls are being developed by OTIS-TTD and Del Rey Systems to control the operation of automated transit systems. The command and control system will allow economical, flexible, personalized service while operating a large number of closely spaced (short headway) vehicles. The requirements for flexible service and short headway operation preclude the use of traditional failsafe design practices and components. To achieve the required performance, reliability, and safety, redundancy and fault-tolerant computer techniques are used. This paper describes how the reliability requirements for command and control systems are achieved through the application of fault tolerant computing. Three alternative computer architectures are described. Reliability analyses have been performed for each candidate architecture, and the results are presented. Based on the reliability analyses, a triple redundant computer is selected. Automatic failure detection and recovery is accomplished by software, thus allowing off-the-shelf hardware to be used.