## 5 Data Processing and Definition of the EAR Index
### Definition of the Normalization and Weight Values  
The identification of factors for normalizing the environmental parameters started from the following considerations:  
* The parameters PERE and PENRE, related to resource consumption, are defined as a linear combination of other parameters namely: \[PERE=PERM-PERT\] (1) \[PENRE=PENRT-PENRM\] (2) Therefore, it was decided not to directly consider PERE and PENRE for the calculation of the EAR index in order to avoid redundancies. * At the current state of technology, the measurement of fresh water consumption and energy consumption material production data is highly error-prone. Therefore, in the current definition of the index, these parameters have been associated with a weight of zero. Nevertheless, the index has been defined so that these parameters can be included in the future as a result of advances in measurement technologies. * For normalization purposes, it was necessary to distinguish factors into _positive_ versus _negative_ ones. Positive factors mean those parameters whose environmental impact is lesser the greater the value presented by them. Conversely, negative factors are those parameters for which an increasing value implies a greater environmental impact. For example, the SM factor is considered a positive factor since it represents the number of materials used in the mixture and obtained from recycling processes (such as, for example, milled material or synthetic aggregates obtained from blast furnace slag). On the contrary, GWP represents the global warming potential in terms of kg of CO\({}_{2}\) equivalent for which a higher value implies a higher negative impact on the environment. The factors labeled as positive are: PERM, PERT, SM, and RSF, CRU, MFR, MER, EEE, EET. * For all indicators, the normalization factor has been assumed to be equal to the maximum value obtained from the investigated sample consisting of EPD-certified mixtures. The values of the weights have been identified through a preliminary assessment of the most significant impacts of the entire asphalt production process. In general, it is important to note that the impacts falling into category [A]--Emissions and impacts falling into category and [B]--Use of resources, are mutually influenced, especially since the production of CO\({}_{2}\) is directly related to fuel consumption. The sum of the weights associated with each category has been set equal to 10. The highest weight was associated with GWP, while all factors associated with category [B] were given the same weight (with the exception of the PERE, PENRE and FW parameters as discussed above). The normalization factors (indicated as \(V_{\rm n}\) in the following), have been established as the maximum values reported in the EPD considered in the present study with the addiction of the impacts due to the phases A4 and A5. Both normalization and weight factors (indicated as \(w_{\rm f}\) in the following) are reported in Table 7.  
For the calculation of the EAR index, the absolute value of each environmental parameter \(v_{\rm m}\) is normalized through the normalization factor \(V_{\rm n}\) obtaining a value that expresses the relative impact \(I_{\rm f}\) of each environmental parameter:  
\[I_{\rm f}=\frac{v_{\rm m}}{V_{\rm n}} \tag{3}\]  
The weighted value \(v_{\rm w}\) for each parameter is obtained as a combination of the relative impact and the weighting factor according to the following relationships:  
\[v_{\rm w} =I_{\rm f}\cdot w_{\rm f}\ \ \text{for all positive impacts} \tag{4}\] \[v_{\rm w} =(1-I_{\rm f})\cdot w_{\rm f}\ \ \text{for all negative impacts} \tag{5}\]  
the overall value for each category is derived as the sum of the respective contributions. For convenience, the results of the three different sums are indicated with the same symbol associated with the environmental impact category (i.e., \(A\), \(B\) e C).