Influence of the city geometric features on the two fluid model parameters

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Virginia Tech

The traffic flow in an urban street network is a complicated system which involves many variables. Some of these variables relate to the network's geometric features; some of these variables reflect the characteristics of the vehicles, drivers and pedestrians using the network.

The Two Fluid Model was introduced to help evaluate the quality of traffic service in urban street networks. The model parameters, Tm and n, are used as a scale to compare traffic quality in two or more urban street networks. It is known that the higher the values of the two parameters in a network, the lower the quality of the network's traffic service.

This report presents material which may be used to predict the correlation between the Two Fluid Model parameters and the geometric features of a specific street network.

The Two Fluid Model parameters will be used as dependent variables in this analysis. Seven network geometric features were selected to be used as independent variables. Using linear regression techniques, the variables will be analyzed to formulate two models. One model will explain the relationship between Tm and corresponding geometric features; the other model will explain the relationship between Tm and its corresponding features. A basic understanding of these two models will allow traffic engineers to develop strategies and/or network changes to improve traffic service in a city's street network. This will especially help networks still in the planning and/or design stage.

Because the trip time per unit distance, T, is an important traffic variable for both the Two Fluid Model and in fuel consumption models, portions of this report concentrated on establishing a relation between the two models.