## 3 Experimental Results
### Collision Load  
In order to analyze the functionality of DCP, it was necessary to evaluate whether the course of the derailed train was intentionally controlled and whether it robustly resisted the impact load caused by the collision with the derailed train. The speed of the flat wagon measured just before the derailment was 51.16 km/h. The derailed wheels collided with the sleeper humps of the concrete track immediately after derailment. Subsequently, the inner wheels continuously collided with the DCP, thereby containing lateral movement, as shown in Figure 10. Through the top-view high-speed camera image, Figure 11 shows more clearly that it prevented the derailed vehicle by DCP installed within track gauge from deviating excessively in the lateral direction.  
Figure 10: Post-derailment behavior of the flat wagon (1 st wheels of front bogie).  
Figure 9: High-speed cameras.  
The collision (impact) load through the experiment can be calculated by [PERSON]'s second law. In the results of the actual vehicle collision test conducted in previous studies [22], it was analyzed that the magnitude of the collision (impact) load estimated by the vehicle acceleration data may have been overestimated. This was because, in the case of a long vehicle such as a trailer, only a portion of the total mass is reflected in the collision load calculation. The collision load through the simulation can be calculated by [PERSON]'s second law or from the contact force between the wheel and DCP.  
In order to verify the method for calculating the collision load between the derailed train and DCP, the collision load according to [PERSON]'s second law and the contact force by the simulation were compared and analyzed. The contact force by the simulation was estimated using the analysis method and simulation model developed and verified in the previous paper [21].  
The raw and filtering data using the 50 ms moving average method for the lateral acceleration of the flat wagon through experiments are shown in Figure 12. At 0.49 s, the first wheel of the front bogie collided with the DCP, and at 0.62 s, the second wheel of the front bogie collided with the DCP. The lateral contact force for each wheel obtained through the simulation results is shown in Figure 13. It can be seen that the maximum lateral acceleration and lateral contact force were generated when the second wheel of the front bogie collided with the DCP.  
Figure 11: Post-derailment behavior of the flat wagon (top view).  
Figure 12: Lateral acceleration of the flat wagon: (**a**) raw and filtering data and (**b**) the point at which the wheels collided with the DCP.  
Figure 13: Cont.  
In the case of the test flat wagon in this study, when the second wheel of the front bogie collided with the DCP after derailing, the rear bogie was still on the rail, so it can be assumed that 50% of the total mass was involved in the collision load. Table 2 shows the comparison of the contact force (simulation result) generated when the second wheel of the front bogie collided with the DCP and the collision load (experimental result) using Newton's second law. In Table 3 and Figure 14, it can be seen that the collision load by the experiment considering only 50% of the total mass agreed well with the contact force by the simulation. That is, when the front bogie of a derailed railway car collides with the DCP, if the rear bogie has not yet derailed, it can be seen that the mass contributing to the maximum collision load at this time is 50% of the mass.