Showing papers on "Traffic count published in 1984"

Estimating time-dependent trip matrices from traffic counts

Abstract: The analysis of dynamic congestion problems in urban areas often requires the use of trip matrices estimated for different consecutive time periods, typically 15-20 minutes. The paper describes an extension of an entropy maximising model to estimate trip matrices from traffic counts to cover this requirement. The new model was implemented and tested in combination with Contram, a traffic management simulation model developed at the Transport and Road Research Laboratory. The results from these tests were very encouraging as the matrices obtained were more accurate than those resulting from using simpler approaches. A further extension to the basic model to incorporate variable accuracy of traffic counts is also discussed. (Author/TRRL)

Estimating origin destination matrices from observed flows

Abstract: The high cost of surveys, combined with the trend in transportation planning towards a shift from long term planning studies to intermediate and short term planning with limited budgets, has led in recent years to the development of low cost techniques for estimating trip matrices from network data. This paper provides a comprehensive review of current models and methods for estimating trip matrices from traffic counts. For the covering abstract of the conference see IRRD no 283191. (TRRL)

A systems dynamics approach to the estimation of entry and exit o-d flows

Abstract: After a review of recent approaches to determine traffic flows from traffic counts at complex traffic facilities a new method for the estimation of the origin-destination matrix is presented. For this purpose traffic flow in the facility is treated as a dynamic process. The model uses the information contained in the time sequences of the traffic volumes at the entries and exits at a complex intersection and solves the problem with a parameter optimisation technique satisfying the given constraints exactly. The comparison with real and synthetic data proved the new method to be superior to previously published approaches to the problem. Because of the efficiency of the algorithm, the procedure could be implemented on a microcomputer at the control site giving online the data basis for traffic responsive control. (Author/TRRL)

Log-linear models for the estimation of origin-destination matrices from traffic counts: an approximation

Abstract: Origin-destination matrices play a fundamental role in transport planning and analysis as well as in traffic management and control However, their estimation by direct means such as interviews, licence plate surveys and aerial photography is both time consuming and expensive, as well as being unsuitable for on-line applications where the matrix is to be frequently updated Therefore indirect procedures based on traffic counts and various forms of route assignment information have received much attention recently These procedures are reviewed in the paper In particular, a family of log-linear models has proved popular although iterative calibration of the models is required This paper suggests a non-iterative procedure for obtaining an approximate log-linear model solution It is suggested that this approximation is particularly suitable for on-line applications Certain statistical properties of the approximate solution are discussed, and a relationship to Bayesian estimation is shown The closeness of the approximation is examined empirically and is found to depend strongly on the quality of the prior information (Author/TRRL)

International Calibration Study of Traffic Conflict Techniques

Abstract: Following discussions at the Copenhaguen preliminary meeting, agreement was reached on the detailed design of the calibration study and the data treatment procedure. These can be summarized as follows:

Passenger car unit values for urban roads

Abstract: The passenger car unit (pcu) value of each class of vehicles has been found to be of prime importance in the study of mixed traffic flow, particularly in studies concerning traffic flow parameters, capacity, signal design and parking lots. Though the pcu values to be used for the different classes of vehicles on rural road stretches have been proposed by the Indian Roads Congress, the values for urban road stretches, intersections and kerb parking have not yet been standardised for use in India. A study was conducted on typical urban roads so as to cover different aspects of road geometrics, traffic and environmental conditions. A model has been developed for arriving at pcu values. Three sets of pcu values have been worked out for (i) urban road stretches (mid-block sections), (II) signalized intersections, and (III) kerb parking. These values may be tentatively adopted on urban roads in India until more rational and variable design vehicle units dependent on roadway and traffic factors are developed. (TRRL)

Traffic monitoring review 1984

Abstract: This review summarises and comments on the results of all phases of the GLC traffic monitoring program which were completed up to the end of 1983. Six chapters cover: 1, introduction; 2, brief description of the traffic monitoring program; 3, summaries of results; 4, daily traffic patterns; 5, estimates of vehicles in traffic; and 6, general summary and conclusions. There are two appendices: 1, summary of selected link counts, 1980 -83; and 2, effects of completion of M25 orbital motorway around North and East London. (TRRL)

Estimating origin-destination flows by simulating trip choice

Abstract: For many traffic studies it is necessary to know the numbers of trips from origins to destinations, but it is difficult and expensive to measure such data This paper describes a new method which is being developed to estimate o-d trip tables from counts of average traffic flows The method, called modcost, is based on a simulation of the choices made by several thousand individuals whose different perceptions of the costs of options is represented by a randomisation procedure The accuracy of the method is assessed using a data-set from a medium-sized town and comparisons are made with other methods of estimating o-d trip tables (Author/TRRL)

Optimizing traffic count program : a methology for estimating AADT volumes from short-duration counts

Abstract: Estimates of annual average daily traffic (AADT) volumes are important in the planning and operations of state highway departments. These estimates are used in the planning of new construction and improvements of existing facilities, and, in some cases, in the allocation of maintenance funds. It is, therefore, important that any method used in obtaining the estimates provide data of sufficient accuracy for the intended use. This importance of having reliable and current data on traffic volumes at hand is generally recognized, and over the years data collection programs have tended to expand. This expansion has led to huge amounts of money being spent annually for the collection and analysis of traffic data. Renewed efforts are, however, now being made to reduce the annual expenditure on traffic counts while at the same time maintaining the desired level of accuracy. A study is, therefore, being carried out by the Council to develop an optimal counting program for the state. This interim report presents the results of that portion of the study in which the feasibility of estimating AADT volumes from short counts was established. The procedure was first to use 1980 data for 16 continuous count stations to determine periods that are stable throughout the year for different short counts. It was found that stable periods for short counts occurred mainly on Mondays, Tuesdays, and Wednesdays, and expansion factors were then developed for short counts of different durations and different starting times for these days. The expansion factors were then used to estimate 1981AADT's from short counts extracted from data obtained in 1981 continuous counts. The results indicate that relative errors of less than 10% were obtained for AADT's estimated from counts of 6-, 8-, 10-, and 12-hour durations on Mondays, Tuesdays, and Wednesdays-The results for Tuesdays and Wednesdays tended to be more accurate than those for Mondays, and counts taken between February and November tended to give more accurate results than those taken in January and December.

Road pricing in hong kong

Abstract: The proposed installation of an electronic road pricing (ERP) system in Hong Kong iss briefly described. Major components of the system are (1) electronic number plate (ENP) fitted to vehicles, (2) toll site comprising a loop array in the road, an outstation and optional toll signs, (3) data transmission system, (4) control centre, (5) CCTV enforcement system which records and transmits to the control centre photographs of vehicles about which there is a query. Potential advantages of the system in providing traffic engineers and transport planners with historical and real time data on traffic counts, axle counts, routes, journey times and trop matrices are also discussed. (TRRL)