Pavement DesignOne of the most aesthetic and functional parts of a roadway is the pavement. The importance of a good pavement design is incredibly important to both the use of the roadway and the design life of the roadway. Pavement is made up of 4 layers and each of these layers needs to be considered within the design requirements which will be derived from the type of use that a pavement will see. These layers include a Sub-grade, Sub-base, Base and Wearing Surface.Pavement Interactive, Civil and Environmental Engineering, University of Washington, URL: http://www.ce.washington.edu/research/construction/images/Pavement%20Layers.JPG

Using Traffic data and preliminary traffic systems design we can examine the requirements of a pavement design in order for it to be suitable for use. The traffic requirements of an underpass will be quite significant based on recent traffic data estimates, the traffic load will be severe with an estimated AADT for all vehicles of 80,000 on South Rd at the intersection.NDT = design life (Heavy Vehicle Axle Groups, or HVAG) = 365 x (AADT x DF) x (%HV/100) x (NHVAG) x (LDF x CGF)Design Life 40 YearsP= 40R=3%

CGF= ((1.03)^40-1)/0.03=75.4 yearsAADT= (29,385+27712)/2= 28,548.5NHVAG= Urban 2.5Damage per HV axle group = urban 0.7 ESALDF=0.65DF=1%HV=4.6%NDT = 365 x (AADT x DF) x (%HV/100) x (NHVAG) x (LDF x CGF)NDT= 365*(28,548.5)*1*(4.6/100)*2.5*(1*75.4)=90,353,575.8775DESA=0.9*90,353,575.8775=81,318,218.2897=81e6The DESA figures of 81e6 are very high and will require a strong and durable pavement design in order to satisfy the design life of 40 years for the underpass.There are 10 different categories of Pavement design with the strongest pavements suitable for heavy use being a Flexible composite pavement, Deep strength asphalt pavement, Full depth asphalt pavement and Concrete pavement. These types of concrete will be suitable for use in our underpass which will see very high loads, with costs being the highest for the Concrete pavement and lowest for the Flexible composite pavement.Design profiles vary but most consist of the required pavement layers and seals between the layers.

Supplement to Part 2: Pavement Structural Design of the Austroads Guide to Pavement Technology