Synthesis of design and construction practices

A sensitivity analysis examining the effect of traffic on the PW of agency costs was 

effective for vey high traffic volumes.  This evaluation involved the computation of total agency 

costs at different traffic volumes.  ESALs ranges of 33, 67 and 135 million over the design life 

were considered. 

Traffic growth curves were created for the 50-year LCCA analysis period for each AADT 

curve (i.e., approximately 67,000,000 ESALs) were shifted according to the ESALs required for 

the same pavement structures to reach a maintenance or rehabilitation trigger (Table 13).  The 

increase in ESALs can be due to an increase in the traffic volume or an increase in the 

percentage of trucks.  A reconstruction was scheduled for the highest traffic alternative in year 

35, except for the composite with CRCP base pavement.  The present worth computations for all 

the alternatives using a discount rate of 4% are summarized in Figure 14.  It should be noted that 

the assumed maintenance schedule for the composite with CRCP base pavement was not 

changed with the increased traffic.  This assumption was based on the experiences reviewed in 

the literature; however, it would need to be verified experimentally before strong conclusions can 

be drawn. 

It can be observed that as the ESALs increase, the PW of all alternatives increase as well, 

base composite pavement remains with a constant PW cost because of the assumption that only 

periodic functional mill and replace every 10 years is required to accommodate very high 

volumes of traffic; approximately 400,000,000 ESALs (U.K., 2006).  The sensitivity analysis 

suggests that CRCP base composite pavements have the potential to save significant agency 

costs when considered for very high-volume high-priority highways (approximately 140 million 

ESALs or greater).   

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