## 4 Discussion
### Discussion of the Results of the ATV-Quad Rollover Tests with ROPS  
A second series of tests were performed to calculate the rollover angle of an ATV-Quad equipped with ROPS. From all the commercial ROPS, an AIR_ROPS was chosen, which remains folded in a normal situation, but it is able to unfold in less than 300 ms in the case of a rollover. In this series of tests, an ATV-Quad YAMAHA GRIZZLY 660 was used.  
Test 2a. Rollover angle measurement of an ATV-Quad without a ROPS.  
In test 2a, the driver did not use a safety belt.  
As it was shown in previous tests, following Table 7, it can be seen that the presence and dimensions of the driver significantly influences the rollover angle.  
Test 2b. Rollover angle measurement of an ATV-Quad without dummy.  
The results of the test 2b, which can be seen in Table 8, show that the presence of a ROPS may slightly influence the angle of rollover.  
Test 2c. Rollover angle measurement of an ATV-Quad equipped with a dummy of 100 kg.  
In these tests, the driver used a safety belt only if the ATV-Quad was equipped with a ROPS.  
The results of the tests 2c, represented in Table 9, show that unfolding the AIR-ROPS decreases the rollover angle, as well as removing it, since the absence of a safety belt produces the slipping of the dummy. A picture of the rollover angle in a right side test of the ATV-Quad can be seen in Figure 21.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Test** & **Angle** \\ \hline Left side & 32.8\({}^{\circ}\) \\ Right side & 31.6\({}^{\circ}\) \\ Frontal & 44.3\({}^{\circ}\) \\ Rear & 41.1\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table}
Table 6: Results of test 1d.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test** & **Without ROPS** & **ROPS Folded** & **ROPS Unfolded** \\ \hline Right side & 51.0\({}^{\circ}\) & 50.5\({}^{\circ}\) & 48.5\({}^{\circ}\) \\ Rear & 60.0\({}^{\circ}\) & 59.8\({}^{\circ}\) & 59.5\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table}
Table 7: Rollover angle measured in tests 2a.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test** & **Without ROPS** & **ROPS Folded** & **ROPS Unfolded** \\ \hline Right side & 38.4\({}^{\circ}\) & 41.9\({}^{\circ}\) & 39.5\({}^{\circ}\) \\ Rear & 48.7\({}^{\circ}\) & 45.2\({}^{\circ}\) & 44.8\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table}
Table 8: Rollover angle measured in tests 2b.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Test** & **Without ROPS** & **ROPS Folded** & **ROPS Unfolded** \\ \hline Right side & 51.0\({}^{\circ}\) & 50.5\({}^{\circ}\) & 48.5\({}^{\circ}\) \\ Rear & 60.0\({}^{\circ}\) & 59.8\({}^{\circ}\) & 59.5\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table}
Table 8: Rollover angle measured in tests 2b.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Test** & **Without ROPS** & **ROPS Folded** & **ROPS Unfolded** \\ \hline Right side & 38.4\({}^{\circ}\) & 41.9\({}^{\circ}\) & 39.5\({}^{\circ}\) \\ Rear & 48.7\({}^{\circ}\) & 45.2\({}^{\circ}\) & 44.8\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table}
Table 9: Rollover angle measured in tests 2c.  
As a result of this second series of tests, it can be concluded that a ROPS in combination with the use of a safety belt may reduce the potential injuries of the driver, as well as increase the rollover angle.  
Additionally, the use of an AIR-ROPS increases the rollover angle when compared with the behavior of an ATV-Quad with a conventional ROPS.