## 4 Results and Discussion
### Measurement Results with Hatchback
At the same bend radius, the theoretical speed at the limit of overturning was reduced by 7.66 km.h\({}^{-1}\), i.e., 8.74%. Additionally, the authors of publication [82], who have selected a bus for their research, point to the reduction of speed driving at the limit of overturning and to the increase in the center of gravity's height. A summary of the results from Tables 5 and 6 is shown in Figure 7, in which the position of the center of gravity at each type of load stowage of hatchback is displayed. Each color represents the type of load stowage and considers the distance of the center of gravity from the axles as well as its height. Every time the load was transferred, the center of gravity shifted too, either vertically or horizontally, or both, as also displayed in Figure 7. The lowest center of gravity was in the empty vehicle (Figure 7, light blue color), or in the empty vehicle with a fitted empty roof box (yellow color). However, when driving with the empty roof box, the center of gravity would shift rearward since the air resistance of the roof box would act rearward too. Reducing the load of the front axle and loading the rear axle would increase with increasing speed of driving, which is also described in the publication focused on dynamics of road vehicles [83]. Using the roof box and the center of gravity's height would also be important for the crosswind's effect on the vehicle stability while driving in the bend [84]. The empty \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Variant**} & \multirow{2}{*}{**hc (cm)**} & **Change (\%)/** (m)** & **Theoretical** & **Change (\%)/ (km-h\({}^{-1}\))** & **Theoretical** **Rollver Angle** (c)** \\ \hline Empty vehicle & 0.56 & 0 /0 & 87.65 & 0/0 & 50.71 \\ Load in the luggage compartment & 0.62 & 10.71/0.06 & 83.20 & \(-\)5.07/\(-\)4.45 & 51.70 \\ Load on the rear seats & 0.63 & 12.5/0.07 & 82.53 & \(-\)5.84/\(-\)5.12 & 51.25 \\ Load in the luggage compartment and in the roof box & 0.65 & 16.07/0.09 & 81.23 & \(-\)7.33/\(-\)6.42 & 50.37 \\ Load in the roof box only & 0.66 & 17.86/0.10 & 80.60 & \(-\)8.04/\(-\)7.05 & 49.94 \\ Load on the rear seats and in the roof box & 0.67 & 19.64/0.11 & 79.99 & \(-\)8.74/\(-\)7.66 & 49.51 \\ Load on the rear seats, empty roof box & 0.63 & 12.5/0.07 & 82.53 & \(-\)5.84/\(-\)5.12 & 51.25 \\ Load in the luggage compartment, empty roof box & 0.62 & 10.71/0.06 & 83.20 & \(-\)5.08/\(-\)4.45 & 51.70 \\ Empty vehicle, empty roof box & 0.56 & 0/0 & 87.65 & 0.00/0.00 & 50.71 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The height of the hatchback’s center of gravity and the theoretical speed of driving at the limit of overturning. roof box, although there was not any measurable increase in the center of gravity's height, would increase the surface of the vehicle's lateral area [85], which is important for the wind action, and it would also lengthen the arm on which the wind force would have been applied [86; 87]. When driving on unpaved terrain or on a slope, it is necessary to choose such a distribution of the load to reduce the risk of the vehicle tipping over.