Design the flexible pavement using the IRC $37$:$2001,$ for highway expansion of four lane having an initial traffic of $3784,$ rate of growth $5\%,VDF=3\mathrm{.}5,CBR$ is $5\%,$ construction period is $2$ years and design life is $15$ years. Use the design chart provided to read the thickness. Also Explain the two critical failures that are in$-$cooperated while designing the pavement using IRC $37$:$2001.$