## 4 Results  
### Longitudinal Accelerations  
If we examine longitudinal accelerations, which are important from the point of view of load securing in the forward and rearward directions, we have to distinguish between the different directions, as the vehicles do not behave the same in both directions. In the forward direction, the deceleration values are more intense than when the vehicle is starting up, and, therefore, the vehicle has higher negative acceleration values here. The forward direction is considered the most critical direction for load securing and transport stability of load units, because, for vehicles with a gross vehicle mass (GVM) above 3.5 t, the designed acceleration for load securing and transport stability of load units in road transport according to EN 12195-1:2010 [40] in the forward direction is 0.8 g and, in the rearward direction, 0.5 g, with an evaluation time of 1000 ms, according to EN 12642:2016, being essential. In Table 3, we can see the maximum and minimum values of the accelerations on the x-axis at the times of 80 ms, 300 ms, and 1000 ms from all testing routes. The minimum acceleration values were measured on the motorway in Austria (see Figure 5) at all three evaluation times (the same acceleration event). This occurred during a braking of a duration of 1.2 s from 80 km/h to 70 km/h; i.e., it was not a sudden hard braking to a stop as performed in the braking tests. The maximum acceleration values of the semi-trailer combination were measured on the road in Slovakia at all three evaluation times (the same acceleration event) during the acceleration from 0 to 22 km/h. A similar maximum acceleration \(ax1000=0.22\) g was also achieved on the highway in Austria and Germany. The designed rearward acceleration of 0.5 g is normally achieved by braking the semi-trailer in the rearward direction, which itself was not used even once during the test runs. This shows that the semi-trailer combination does not accelerate by more than half of the designed rearward acceleration. Higheraccelerations rearwards can occur during hard braking rearwards which is generally not used during regular transports but is used during braking tests as per EN12642:2016. Figure 5: Acceleration events in the ax1000 (absolute values) from 0.1 g to 0.5 g (**top**) and from 0.2 g to 0.5 g (**bottom**) with the indication of selected parking and highway intersections on OSM map layer. \begin{table}
\begin{tabular}{c c c c c c c c} \hline  & & **MIN** & **MAX** & **MIN** & **MAX** & **MIN** & **MAX** \\  & & **ax80** & **ax80** & **ax300** & **ax300** & **ax1000** & **ax1000** \\ \hline Slovakia & Highway & –0.235 & 0.183 & –0.204 & 0.172 & –0.187 & 0.146 \\  & Road & –0.505 & 0.276 & –0.463 & 0.261 & –0.395 & 0.222 \\ \hline Austria & Highway & –0.660 & 0.248 & –0.623 & 0.245 & –0.492 & 0.221 \\  & Road & –0.325 & 0.180 & –0.311 & 0.174 & –0.259 & 0.165 \\ \hline Germany & Highway & –0.213 & 0.242 & –0.202 & 0.238 & –0.193 & 0.217 \\  & Road & –0.330 & 0.210 & –0.324 & 0.201 & –0.295 & 0.188 \\ \hline  & Total & –0.660 & 0.276 & –0.623 & 0.261 & –0.492 & 0.222 \\ \hline \end{tabular}
\end{table} 
Table 3: Maximum measured deceleration (negative values) and acceleration (positive values) of semi-trailer vehicle combination in longitudinal axis in 80, 300, and 1000 ms evaluation times. It can be seen from the above values that the semi-trailer combination did not achieve the design accelerations for securing the load in the forward or rearward direction in either case, even for the shortest evaluation time of 80 ms. It can also be seen that a higher negative acceleration is achieved during braking than the positive acceleration when the vehicle is accelerated. Table 4 shows the total number of x-axis acceleration events longer than 1 s from all testing routes.