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Expected ESALs Without Additional Heavy Vehicles <br />In this computation, the expected ESALs are computed for the current traffic situation, assuming <br />1 % growth, and without the additional heavy vehicles under consideration. <br />DailyESALs = 0.0004(ADT— HCADT)+ 0.58HCADT (1) <br />ESALs = Dail.y ESALs- 365• (1+i)" —1� 2 <br />Without I� ( ) <br />Z <br />where: <br />i = traffic growth rate, <br />n = analysis period, years <br />Expected ESALs With Additional Heavy Vehicles <br />The expected ESALs contributed by the additional heavy vehicles is computed by considering all <br />the user -entered additional vehicles individually, and summing their contributions to the ESAL <br />calculation for the first year, and then expanding that value to the analysis period. The routine <br />takes the user -entered vehicles from the list shown in the tool's main screen (Figure 6). The <br />vehicle type and its loading state (Full, '/2-Full, or Empty) are used in a look -up table to obtain <br />the ESALs per vehicle. The number of vehicles for that type and the time interval selected are <br />used to expand the expected ESAL per vehicle contribution to the first year. An equation similar <br />to equation 2 is used to compute ESALs contributed by the heavy vehicles. The expected <br />ESALs with additional heavy vehicles (ESALswith) is simply the sum of this value and the <br />"ESALs Without" value calculated in the previous section. <br />Estimate Original Design ESALs <br />The result of the two previous sections is the "ESALs Without" heavy vehicles and the "ESALs <br />With" heavy vehicles over the next design period. One of the computations used in the results is <br />the percent of the original life consumed by the additional heavy vehicles. This value requires an <br />estimate of the original ESALs for which the existing pavement structure was designed. In some <br />cases the tool's user may know this information, or may be able to find it in historical design <br />records. In many cases this must be estimated based on the existing pavement structure. <br />The original design ESALs is estimated by back -calculating the design chart using the layer <br />thicknesses and material types. The first step is to estimate the Granular Equivalent (GE) of the <br />existing pavement, in its as -constructed condition. <br />GEDestgn _ (hi • LayerGEt ) <br />t <br />(3) <br />where: <br />h; = thickness of layer i, <br />LayerGE; = Granular Equivalent per inch of the material in layer i. <br />17 <br />