Showing papers on "Traffic wave published in 1978"

Contram: a traffic assignment model for predicting flows and queues during peak periods

Abstract: The report describes a computer-based traffic assignment and queueing model for use in the design of urban traffic management schemes. The model is called CONTRAM--CONtinuous TRaffic Assignment Model. CONTRAM requires data on time-varying flow demands (for example as occur in a "peak period"), and predicts the flows, delays and queues throughout a network of roads and junctions. The movement of traffic is modelled by grouping vehicles together to form "packets". Each packet is assigned to its minimum journey time route through the network, taking into account delays and queues at junctions. The report is divided into three parts. The first outlines the assumptions and structure of the model. The development of the model, sensitivity tests and validation work are described in the second part and examples to illustrate applications of the model are described in the third part. /Author/

Traffic models for use in vessel traffic systems

Abstract: Traffic management systems for ships are playing an increasingly important role in major ports throughout the world. The function and performance characteristics of these systems are influenced by the physical geometry of the ports and by the dynamics of the port traffic. In a given traffic system intersections between ship routes lead to a potential need for operator intervention to resolve conflicts and promote an orderly and safe flow of traffic. The results in this paper are related to the problem of determining the relative difficulty associated with managing high-density route intersections and for suggesting route structures or regulatory improvements when such flexibility is allowed. The model can be used to distinguish between traffic situations due to high traffic densities and those due to the occurrence of a statistically unusual event. A model is developed for conflicts between ships at route intersections. Quantitative measures are presented for conflict intensity and duration and for intersection capacity. These measures are shown to be related to the geometry of the intersection and to the statistics of the incident flows. An optimum intersection angle is found.

On Traffic Equilibrium, Congestion Tolls, and the Allocation of Transportation Capacity in a Congested Urban Area

Abstract: In a continuous transportation model with a scalar velocity field, dependent on the ratio of traffic to transportation capacity, and with trips generated by a gravity or entropy hypothesis, the equilibrium traffic distribution is derived along with the optimal capacity distribution. Possible improvements by introducing congestion tolls are discussed. It is seen that capacity should be distributed in proportion to traffic, so that velocity of transfer is constant, trips go along straight lines, and traffic is minimized. This implies that capacity is concentrated to the central parts. Congestion tolls are superfluous when capacity is optimally allocated.

The problem-orientation of traffic models

Abstract: With the aid of traffic models, traffic volumes, traffic flows and traffic loads are determined in relation to settlement structure, traffic infrastructure and behaviour patterns of the inhabitants. In small communities with less than 25000 inhabitants the data necessary for the traffic model are usually not available, but it is generally possible to get an overall view of the traffic conditions. The use of traffic models is described for medium-sized towns with 80000 inhabitants. Input data on traffic generation, traffic distribution, modal choice and the choice of route are necessary for the model. Traffic functions are divided in a simplified manner into journeys to work, school traffic and other traffic. Important basic parameters are provided by values for specific traffic incidence with time distributed over the day for shopping traffic, leisure traffic, etc. In large towns whose road network can no longer be measured according to business traffic peaks, a special investigation of commercial traffic is necessary. This type of travel purpose is still some way off incorporation into a model-analysis which is useful for practical traffic planning. Very varied estimates are available for that section of so called inner cell commuters, some of whom travel to work on foot. (TRRL)