## 3 Results and Discussion  
### Acceleration Levels  
Table 3 contains the results of the measured peak acceleration values for all three orientations. On the floor, the highest acceleration levels were recorded in the vertical orientation, followed by lateral, with the least in the longitudinal direction. Concordant results on floor vibration levels have been presented in previous research for small delivery vehicles [3; 5; 6; 7; 10; 15]. However, it is a very interesting observation that the highest peaks of the entire recorded data for this study were in the third layer and in the lateral direction: 4.16g, 4.93g, and 5.94g with 0%, 10%, and 20% FM space, respectively. On the other hand, the highest acceleration in the vertical direction was 3.99g with 20% FM, also in the third layer. This phenomenon can be attributed to heavy curvvy roads on the country road network while traveling with relatively high speed, when the packages in the third layer can bounce into the fences with a high amplitude, first to the right/left side and then to the back. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \begin{tabular}{c} **Acc. Data** \\ **(g, Peak)** \\ \end{tabular} & **FM** & **Location** & \begin{tabular}{c} **Max.** \\ **Acc.** \\ \end{tabular} & \begin{tabular}{c} **Acc. at 99\%** \\ **Occurrence** \\ \end{tabular} & \begin{tabular}{c} **Acc. at** \\ **95\% occ.** \\ \end{tabular} & \
\begin{tabular}{c} **Acc. at** \\ **90\% occ.** \\ \end{tabular} &
\begin{tabular}{c} **Acc. at** \\ **50\% occ.** \\ \end{tabular} \\ \hline \multirow{8}{*}{**Lateral**} & \multirow{4}{*}{0\%} & Floor & 1.24 & 0.68 & 0.46 & 0.36 & 0.18 \\  & & 1 st & 1.41 & 0.79 & 0.56 & 0.45 & 0.24 \\  & & 2 nd & 2.40 & 0.80 & 0.58 & 0.48 & 0.26 \\  & & 3 nd & 4.16 & 1.24 & 0.75 & 0.59 & 0.26 \\ \cline{2-8}  & \multirow{4}{*}{10\%} & Floor & 1.58 & 0.68 & 0.45 & 0.38 & 0.17 \\  & & 1 st & 2.15 & 0.74 & 0.51 & 0.41 & 0.22 \\  & & 2 nd & 2.35 & 1.09 & 0.63 & 0.46 & 0.15 \\  & & 3 nd & 4.93 & 2.50 & 1.39 & 0.98 & 0.33 \\ \cline{2-8}  & \multirow{4}{*}{20\%} & Floor & 1.33 & 0.65 & 0.41 & 0.32 & 0.16 \\  & & 1 st & 1.91 & 0.86 & 0.54 & 0.41 & 0.19 \\  & & 2 nd & 2.81 & 0.84 & 0.55 & 0.43 & 0.24 \\  & & 3 nd & 5.94 & 2.19 & 1.34 & 1.02 & 0.45 \\ \hline \multirow{8}{*}{**Longitudinal**} & \multirow{4}{*}{0\%} & Floor & 0.96 & 0.38 & 0.27 & 0.22 & 0.11 \\  & & 1 st & 1.81 & 0.41 & 0.32 & 0.28 & 0.15 \\  & & 2 nd & 1.94 & 0.72 & 0.49 & 0.39 & 0.16 \\  & & 3 nd & 3.74 & 1.07 & 0.66 & 0.50 & 0.26 \\ \cline{2-8}  & \multirow{4}{*}{10\%} & Floor & 1.11 & 0.55 & 0.35 & 0.27 & 0.13 \\  & & 1 st & 1.72 & 0.59 & 0.38 & 0.31 & 0.19 \\  & & 2 nd & 1.82 & 0.61 & 0.43 & 0.35 & 0.16 \\  & & 3 nd & 2.38 & 0.71 & 0.43 & 0.36 & 0.20 \\ \hline \multirow{8}{*}{**Longitudinal**} & \multirow{4}{*}{20\%} & Floor & 1.56 & 0.37 & 0.26 & 0.21 & 0.11 \\  & & 1 st & 2.08 & 0.67 & 0.43 & 0.34 & 0.17 \\ \cline{1-1}  & & 2 nd & 3.02 & 0.94 & 0.57 & 0.41 & 0.18 \\ \cline{1-1}  & & 3 nd & 3.42 & 1.05 & 0.65 & 0.49 & 0.20 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Summary of measured acceleration (acc.) data. Practically, at each measurement, it could be observed that the highest acceleration levels were in the third layer, followed by the second, first, and floor. This is true for all orientations except the longitudinal direction with 10% FM space, where 50% of recorded event data were higher in the first layer than in the second layer. This latter phenomenon can be explained by different sudden braking conditions due to variable traffic during different measurements. Figure 5 presents the CDFs and also shows the probability of occurrence at a given acceleration level. The data presented in this figure show that 50% of vertical vibration levels are below 0.37\(g\) on the floor and below 0.48\(g\) in the third layer. In the lateral and longitudinal directions, 50% are below 0.18\(g\) and 0.13\(g\), respectively, on the floor and below 0.45\(g\) and 0.26\(g\), respectively, in the third layer.