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32 Upper benefit cutoff value Friction number Overall post-treatment AREA Do nothing curve PT(FRICTION) analysis life of 20 years Lower benefit cutoff value 5 10 15 20 25 Age, years Upper benefit cutoff value Rutting Do PT(RUTTING) AREA nothing curve Overall post-treatment analysis life of 20 years (associated with friction) Lower benefit cutoff value set to zero 5 10 15 20 25 Age, years Upper benefit cutoff value International Roughness Index (IRI) AREAPT(ROUGHNESS) Overall post-treatment Do nothing curve analysis life of 20 years (associated with friction) Lower benefit cutoff value 5 10 15 20 25 Age, years Figure 8. Illustration of the total areas associated with individual condition indicators. friction, rutting, and IRI are 10, 16, and 20 percent, respec- lated for each individual condition indicator. In this example, tively (i.e., when compared with the respective areas associ- the total overall benefit contribution is 14.0 percent. While by ated with the do-nothing option, the preventive maintenance itself this actual total benefit value is essentially meaningless, treatment application results in increases of 10, 16, and 20 per- total benefit values computed for different timing scenarios can cent in the friction, rutting, and IRI areas, respectively). Fur- be used to compare the effectiveness of the different timing ther assume benefit weighting factors of 50, 25, and 25 are scenarios. Results of this example are presented in Table 19. chosen for friction, rutting, and IRI, respectively (note that these factors add up to 100). The overall benefit contributions are then determined by multiplying the benefit weighting fac- Step 9: Cost Computations tor percentages by the individual benefit values (e.g., for fric- tion 10 percent 50/100 = 5.0 percent). The total overall benefit A simple two-step LCCA is conducted to compare the dif- contribution is then computed as the sum of the values calcu- ferent cost streams associated with each preventive mainte-