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25 Pavement failure (rehabilitation trigger)--the condition individual condition indicator areas are computed by taking level at which a major rehabilitation is required. integrals of the specific performance equations that define the Treatment failure--the condition level at which a treat- do-nothing performance curves. The important benefit-related ment is considered failed (i.e., the benefits of the preven- areas are those below condition indicator curves that decrease tive maintenance treatment are no longer being realized). over time and above condition indicator curves that increase over time. The final do-nothing condition area for a given If agencies are unsure about how to select these benefit cut- condition indicator is determined by applying the following off values, it is recommended that values be set to closely area boundary conditions: reflect current maintenance and rehabilitation policies. For example, if an agency typically applies only one preventive Y-axis limits--in the y direction, the pertinent area is maintenance treatment in the life of a pavement, then the bounded by the defined upper and lower benefit cutoff benefit cutoff value should be equal to the pavement failure values. level because a major rehabilitation will most likely be the X-axis limits--in the x direction, the pertinent area is next pavement-related activity. In contrast, if an agency typ- bounded by zero on the lower end and the age at which ically applies a second preventive maintenance treatment the performance curve intersects the benefit cutoff value after the first application reaches a known condition failure on the upper end. level, the benefit cutoff value can be set equal to the treat- ment failure level. The area calculation details differ slightly depending on whether the performance equation is decreasing or increas- Step 3: Computation of Areas Associated ing. Equations 2 and 3 are used to compute the do-nothing with the Do-Nothing Case benefit-related areas associated with decreasing and increas- ing equations, respectively. These equations are functions of The third step in the benefit calculation process involves the actual do-nothing mathematical equation and the upper determining the total do-nothing condition curve areas. The and lower benefit cutoff values. Figure 3 illustrates the total DECREASING RELATIONSHIP UBC = Upper benefit cutoff value Condition Indicator AREADN-TOT(-) LBC = Lower benefit cutoff value X0 X1 X2 Age, years INCREASING RELATIONSHIP UBC = Upper benefit cutoff value Condition Indicator AREADN-TOT(+) LBC = Lower benefit cutoff value X0 X1 X2 Age, years Figure 3. Total areas associated with decreasing and increasing condition indicators for do-nothing options.