A granular pavement with bituminous seal is to be design for a collector road in urban area. The design lane traffic loading in Equivalent Standard Axles (DESA) is 25 million.Deflection testing revealed that the original subgrade CBR of 3% could be improved to an effective CBR of 6% with lime stabilisation. Available equipment and construction techniques dictate that the stabilised subgrade layer must be 300 mm as-compacted and the cost for stabilisation will be $90.00 per m3.The minimum as-compacted thickness of any unstabilised layer is 100 mm.The following materials are available for your use and are as placed.Material CostCrushed rock, soaked CBR 90 $60.00/ m3Coarse river sand, soaked CBR 30 $45.00/ m3Clayey gravelly sand, soaked CBR 15 $20.00/ m3Silty sand, soaked CBR 7 $15.00/ m3Consider possible pavement options (with and without subgrade improvement) and recommend a final pavement configuration (with appropriate sketches) for adoption. It is essential to provide justification as to why you have selected a particular design for construction. While cost is an important issue, include some discussion on the potential long-term performance of the selected pavement as compared with other pavements.Note: The pavement seal has already been designed, and you do not need to design either seal or other road elements such as slopes, drainage, etc.