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Heavy Vehicle Axle Loads The axle loads attributed to each vehicle depends on its loading situation. Based on data from the MnDOT Vehicle Classification Scheme (19) and the MnDOT Weigh -in -Motion (WIM) reports (20) the weights of the various heavy vehicle types can be estimated. The vehicle weight information in Table 4 is averaged several WIM reports in 2013 and 2014 from the Owatonna station at MP 30.1 on I-35. The Average ESAL column in the table is taken from the MnDOT Procedure Manual for Forecasting Traffic on Minnesota's Highway Systems (21). Table 4. Average Vehicle Weight by Classification. Vehicle Class Weight Empty, lbs Weight Full, lbs Weight 1/2- Full, lbs Average ESAL 4 15,000 30,700 22,800 0.57 5 8,000 14,000 11,000 0.25 6 19,000 32,800 25,900 0.58 7 11,500 47,700 29,600 0.58 8 31,000 38,900 34,900 0.39 9 33,000 62,600 47,800 1.13 10 33,500 75,000 54,250 1.13 For vehicles that do not fit one of the classifications in Table 4, the user must create a custom vehicle definition and specify the axle loads and tire configurations. From this information the tool calculates ESAL values for each custom vehicle entered. The ESAL calculations for custom vehicles are taken from the AASHTO Guide for Design of Pavement Structures (2). Analyze Pavement Structure The basic method of estimating damage or impacts to the pavement structure is through the MnDOT pavement design methods (22). The pavement analysis routines in the tool utilize the Granular Equivalent method of pavement design, which requires estimates of the Equivalent Single Axle Load expected over the life of the pavement, and the subgrade resistance value, or R-Value. While the R-Value is a measured property of the soil, the ESALs are estimated based on the current and future predictions of traffic volumes and expected vehicle classifications. The ESAL predictions are based on the ADT, HCADT (or % Trucks), and assumptions of ESAL values per vehicle, according to the MnDOT vehicle classification scheme (19). The following assumptions are made. • All non -heavy commercial vehicles (passenger cars and pickup trucks) have an ESAL/vehicle of 0.0004. • All heavy commercial vehicles have an ESAL/vehicle value of 0.58. • Traffic growth is limited to 1% per year. The next few sections describe the computations involved to estimate the ESALs with and without the added heavy vehicles, and the original design ESALs (if these were not provided by the user). 16