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- Exponential: In this type of model, the pavement condition remains nearly constant for a number of years, and then rapidly deteriorates.
- Hyperbolic: In this type of model, the pavement condition deteriorates steadily with the greatest rate of deterioration occurring in the early years.
- Inverse Exponential: This type of model is essentially the same as the Exponential model type.
- Linear: In this type of model, the rate of deterioration of the pavement condition is the same from year to year.
- Piecewise Linear: In this type of model, you specify up to six coordinates and the system draws a straight line between each coordinate. This type allows you to specify points in time where the rate of deterioration "jumps" to a new value, where it again remains constant until the next discontinuity.
- Power: This type of model is a special form of the exponential type. Like an exponential-type graph, the pavement condition remains nearly constant for a large number of years, and then rapidly deteriorates. However, the rate of deterioration is based directly on time rather than a logarithm.
- Sigmoidal: In this type of model, the pavement condition remains nearly constant for a number of years, then rapidly deteriorates, and then remains nearly constant again.
- Depending on your set up, you may also have
**ITD1**and**ITD2**as model types.

Assign a model type to each user-defined model by using the drop-down list in the Model Type column. Then set the model's parameters by using the **Edit Model Parameters** command (which is found on the right-click shortcut menu). These parameters dictate This allows users to define the parameters of the model's rate of deterioration from a starting constant value.

In addition to user-defined models, models can also be generated via regression analysis in the Performance Models window. You can tell these types of models from user-defined models by looking at the User Update column. This column shows System for models defined via regression analysis. Also, for these models, you are not allowed to edit the parameters.

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# Right-click Shortcut Menu Commands

When you right-click a record in the table, the system displays a shortcut menu with the common commands along with the following special commands:

When you right-click a record in the table, the system displays a shortcut menu with the common commands along with the following special commands:

**Edit Model Parameters**: This command is only available for user-defined models (that is, those that do not show System in the User Update column). When available, it allows you to view and adjust the parameters that determine the model's rate of deterioration for the selected model. After activating this command, the system displays a dialog box that you use to adjust the parameters. Once the parameters are adjusted as desired, click**OK**to save the adjusted model parameters. (You can abort the change process, and return to the previous parameter settings, by clicking**Cancel**.)Note **Note:**All model equations start with a constant value from which the rate of deterioration is subtracted. This constant value should not exceed 100. If a greater value is entered, the system will use 100 instead.**Show Selected Models**: For the model(s) selected in the table, this command displays a new window that shows the selected models on a graph of time versus condition. (Select multiple rows by using either CTRL+click or SHIFT+click.)Note **Note:**The permitted upper value along the Y-axis is always 100. If the function of the curve is to exceed 100, then the system will display the curve as a flat line at 100 until the function of the curve returns to a value less than 100. Similarly, the X-axis always displays 50 years: and if the curve reaches 0 before 50 years, the system will display the curve as a flat line along the X-axis from the X-intercept to 50 years.

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