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11-- ,I, 11 tl <br />`(~\ uJ l l l+ <br />• Equivalent Single Load (ESAL) -the same as the~quivalent Daily Load Application <br />(EDLA)which isthe equivalent number of applications of an 18.000 pound, single axle load <br />during an average 24 hour period. <br />• Total ESALs -The total ESALs is the ESAL value times 365 days per year times the <br />-rtumber-ef-ye`rs in the design period adjusted by a traffic lane factor. <br />CDOT uses a five step pracedure to predict the design total ESAL's used in pavement section <br />design. The five steps are~fiscussed below. <br />~ / <br />Step Ine the Average Daily Traffic (ADT) for the first year and the last year of the <br />design period. Use the appropriate growth factor for the last year of the design period. <br />Calculate the ADT for the midpoint of the design period by adding the ADT of the first year <br />and the ADT of the last year and divide by two. <br />Step 2. Separate the ADT of the midpoint by classification of vehicle. The ADT is <br />separated in to the following three classifications: <br />• Passenger cars and pickup trucks. <br />• Single unit trucks. <br />• Combination trucks. <br />Step 3. Multiply the number of vehicles in each classification by the appropriate 18k <br />equivalency factor. Table 2-7 show the equivalency factors determined by a study of <br />Colorado traffic in 1987. The damaging effect of an axle is different for a flexible pavement <br />and a rigid pavement, therefor there are different equivalency numbers for the two <br />pavements. <br />Table 2-7 <br />18 Ki E uivalenc Factor for Pavement T es <br />Vehitle Classifiation Flexible Pavement Rigid Pavement <br />Passenger nrs 8 pickup tacks 0.003 0.003 <br />Single unit Wtlns 0249 0.265 <br />Combination trucks 1.087 1.692 <br />Add the product of each equivalency factorand numberofvehicles toyield asingle number <br />of ESALs for each pavement type. <br />Step 4. Multiply this number by 365 (days in a year) and the number of years in the design <br />period. <br />Step 5. Multiply the 18k ESAL's for the roadway by the lane factor in Table 2-8. This will <br />be the 18k ESAL for the design lane over the design period. Table 2-8 shows the lane <br />factor that correlates to the number of lanes per direction. <br />,A, <br />z - to s~i_..~.. ~.- - - O1 <br />