According to the 1993 AASHTO Design Guide from a costeffecti

According to the 1993 AASHTO Design Guide, from a cost-effective viewpoint, if the ratio of costs

for hot-mix asphalt (HMA) and granular base is less than the corresponding ratio of layer coefficients

times the drainage coefficient, then the most economical design is to use:

i) Minimum base thickness

ii) Minimum HMA thickness

iii) No base

iv) No feasible design

Solution

For most economical design , the literature review revealed yhaytminimum HMA thickness is to be adopted