Out of the box, the Default Model Structure window is located Pavement Analyst > Setup > Performance Setup > Default Model Structure menu. It shows the decision process that determines what deterioration model to use for a particular type of section. "Type of road" means not only the type of road and how the road section is constructed, but also the condition attributes associated with that road section. Decision trees consist of parent nodes, child nodes, and the branches between them. The nodes are shown as boxes and the branches are the lines connecting the boxes. A parent node requires a user-selected decision variable and user-defined values to distinguish, and branch to, the parent's child nodes. The decision variables that may be used are selected in the Performance Class Variable column in the Setup PMS Analysis Columns window.

Each node of the tree represents the point at which a decision must be made. The tree then branches depending on the result of the decision. The user selects what decision variable is to be used in making the decision as well as the values for that variable that cause the different branches from the node to be selected. The tree is read from left to right, with the leftmost node representing the most general and the rightmost nodes the most specific. Out of the box, the system comes with a default model structure by Pavement Type and AADT level.

The Default Performance Model configured here is then used in the Performance Models window (Pavement Analyst > Analysis > Performance Analysis > Performance Models), where a deterioration model is assigned to the rightmost nodes for each condition attribute.

The following sections describe several operations you can perform in this window:

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