# Practical Application of Sustainable Road Structure: Mechanical and Environmental Approach
## 5 Economic and Environmental Analysis
### Economic Analysis  
The economic feasibility of developed APSE pavement has been assessed at a material level, as well as considering the environmental costs (costs of externalities), comparing the conventional flexible pavement structure with APSE pavement. As mentioned above, the APSE test sections were performed in Poland on a local medium-traffic level road. Given the exact geographical locations of this case study, the costs of the input materials, as well as national standards for pavement structures, the total costs of 1 m\({}^{2}\) of road pavement can slightly varies across other European countries. The economic feasibility of APSE pavement has been assessed following the methodology described in ISO standard [31]. The cost-effectiveness of innovative materials has been evaluated, comparing APSE pavement with conventional pavement. According to the international guidelines, the following four phases of pavement life cycle are investigated within the life cycle costing analysis (LCCA): 1--Construction, 2--Operation, 3--Maintenance & Rehabilitation and 4--End-of-life. Additionally, the environmental costs throughout the life cycle stages of pavement are quantified. As a functional unit in the study is chosen 1 m\({}^{2}\) of road structure. Therefore, the costs of 1 m\({}^{2}\) of road are compared across the pavement alternatives. The estimated costs throughout the life cycle of the pavement are discounted to the base year of the analysis to determine the Net Present Value (NPV) for the pavement alternatives. Based on the recommendations of European Commission [32], the discount rate selected within the scope of this analysis is 4%. The model developed in Excel by authors allows to quantify the construction costs of APSE and conventional road pavements and identify the cost-effective alternatives.  
Based on the LCCA calculations performed, it was found that using 30% RAP with BIO-additive in binder- and base- layers implies up to 18% and 20% reduction in the costs of these layers. Moreover, the substitution of virgin aggregates with CDW reduces the cost of this layer by 67% (Figure 8).  
The total material costs during road production stage were approximately 30% lower, compared to baseline in Poland.  
As part of the LCCA, the environmental costs of pavement structures were estimated by allocating shadow price on the environmental impacts quantified within the LCA. The  
Figure 8: Materials costs of flexible pavement in Poland, total costs of 1 m\({}^{2}\) of conventional and apse road pavement.  
environmental costs of 1m\({}^{2}\) of APSE pavement was estimated to be EUR 68.14, or 27% lower than of conventional pavement (with 0% RAP and virgin aggregates (Figure 9).  
Considering the costs of materials, as well as environmental costs of externalities (based on the life cycle impact assessment results), it can be estimated that over 60 years of pavement's life cycle, APSE concept can lead to 25% reduction in total costs, applying 4% discount rate (Figure 10).  
Figure 10: Total life cycle costs (in NPV) of pavement structures, considering costs of materials and costs of externalities.  
Figure 9: Environmental costs of 1 m\({}^{2}\) of pavement structure.  
Nowadays, application of up to 20% of RAP directly to the mixer, in binder and base layers and use of CDW in sub-base becomes a common practice. The use of BIO-additive allows to increase the RAP content to 30% (without extra heating), thereby achieving approximately 4% reduction in the total costs of pavement structure.