Lime stabilization is commonly used to improve weak natural subgrade in Illinois. ILLI-PAVE nonlinear finite element (FE) program was utilized in this study as an advanced pavement structural analysis tool to quantify the improvement from the lime stabilized soil layer in conventional flexible pavements. Using ILLI-PAVE, many combinations of typical Illinois highway pavement layer thicknesses and material properties were analyzed to establish a database of surface deflections and critical pavement responses. Using this database, Artificial Neural Network (ANN) structural models were trained successfully as forward analysis tools, surrogate to ILLI-PAVE, to be used in the backcalculation of the Falling Weight Deflectometer data. The ANN model predictions were on the average within 1% of the ILLI-PAVE FE results. The developed ANN models were therefore quite accurate for the rapid analyses of conventional flexible pavements built on lime stabilized soils replicating the ILLI-PAVE results.