## 3 Results  
From 2015 to 2020, the CDV performed measurements on the wearing course of a total of 111 sections with the SMA 11S surface and 112 sections with the EACC 8 surface within the modernised stretch of the D1 motorway (21 to 182 km). The number of measured sections is increasing every year (Figure 5), which is related to the ongoing modernisation of the D1 motorway, as new modernised sections are gradually being put into operation (the first modernised sections were commissioned at the end of 2014). The largest number of measurements (Figure 6) was carried out in spring in April, from May the number of measured sections gradually decreased and in September and October, only a small number of sections was measured. This is due to the fact that in spring, the temperature  
Figure 4: The exposed aggregate cement concrete surface with the highest grain size of 8 mm (EEAC 8) on the left and stone mastic asphalt surface with increased resistance to permanent deformation with the highest grain size of 11 mm (SMA 11S) on the right (source: CDV).  
conditions are optimal when the temperature varies between 15 and 20 \({}^{\circ}\)C. Measurements from August to October take place only on newly constructed sections, which are usually put into operation in autumn, because all works must always be completed before winter in order to keep the D1 motorway passable without restrictions during the winter months.  
The resulting values measured for both surfaces are summarised using a table, box plot and by fitting the values. The tables provide a basic statistical analysis of noise levels in each year of surface life. It shows the arithmetic mean and median, the minimum and maximum measured noise values for each year of surface life and the standard deviation (generally, the average deviation from the mean). Box plots are connected to the tables. The white square point inside the rectangle indicates the mean value. In the box (rectangle), the lower and upper parts represent the lower (25%) and the upper (75%) quantile, respectively, and the horizontal line represents the median (50% quantile). The narrower the rectangle, the smaller the data variance. Lines continuing from the opposite sides of the rectangle assess symmetry at the ends of the division. Their ends correspond to 5% quantile (bottom  
Figure 5: Number of measured sections within the framework of the monitored sections of motorway in individual years.  
Figure 6: Number of measured sections within the framework of the monitored sections of motorway by month of the year.  
line) and 95% quantile (upper line), or they can mark the minimum and maximum. Points outside the described grouping are outliers.  
When describing the road surface lifetime in years, year zero means the noise level in the year of construction of the road surface. Therefore, if the surface was constructed in 2015, then the measurement carried out in 2015 is marked as year 0, measurement from 2018 as year 3, etc. However, there are some overlaps. If the surface was constructed, for example, in November (when the conditions are no longer suitable for the measurement using CPX) and the measurement is carried out in April of the following year, then it is marked as year 1. The surfaces were measured in years 0-6. The age of the surface of six years relates to the road sections put into operation at the end of 2014 (in November), but the first measurement of noise levels took place in the first year of their service life, i.e., in 2015. Therefore, the number of values for life cycle years 0-6 (7 values) and the number of years of measurement 2015-2020 (6 years) do not match.