This study utilized Illinois DOT (IDOT) mechanistic-empirical (M-E) technology and Mn/ROAD mainline pavement section data and information to verify/refine/modify IDOT M-E analysis and design concepts and procedures for full-depth asphalt concrete (FDAC) and conventional flexible pavements (CFP). The Mn/ROAD mainline flexible pavements include eleven CFP and three FDAC pavement sections. Four different granular materials were used in the conventional flexible pavements. A fine-grained soil subgrade (R-value of about 12) is present throughout the mainline. Laboratory material testing results, field distress measurements, and FWD test data were used to study pavement deflection response and performance (rutting and asphalt concrete fatigue). The study demonstrated that the IDOT M-E analysis and design procedures for FDAC and CFP sections are adequate. The ILLI-PA VE structural model adequately predicts the pavement responses. The use of bi-linear (arithmetic) subgrade model and the "theta" granular material model ILLI-PA VE inputs closely replicate CFP field FWD deflection responses. The effect of granular material quality on CFP deflection response is very limited. The ILLI-PAVE FWD backcalculation algorithms are adequate for estimating the moduli of asphalt concrete and sub grade soils.