## 4 Conclusions and Recommendation  
### Conclusions  
The purpose of this research was to find out potential factors for Bogie Instability Detection System (BIDS) alarms and possible solutions to reduce wheel/rail interface concerns subject to BIDS alarms, so that operating costs and maintenance costs can be reduced.  
Based on experiment results in this study, it can be inferred that temperature change is the main factor. However, the rules for this factor can vary from T1 to T4.  
According to decision trees, all generated rules have their own forming orders. Hence, aside from temperature as the main factor for BIDS alarms, train speed, accumulated mileage and location are subordinate factors. As to reduce the number of BIDS alarms, there are some improvements that can be made which are described in detail in the following:  
1. Temperature  
From experiment results, when temperature falls from group T1 to T3, the number of BIDS alarms increases. However, temperature is a factor that is difficult to control. Moreover, THSR cannot plan its schedules due to temperature change. Therefore, there are no possible improvements that can be made to temperature.
2. Train speed  
From experimental results, when temperature falls from group T1 to T3, it is very likely that alarms occur due to train sets belonging to group S4; therefore; reducing train speed can improve the number of BIDS alarm occurrences. However, it must also be considered that reducing train speed can possibly lead to trainset errors and also reducing train services. Therefore, although it is an effective factor to reduce BIDS alarms, it can lead to serious problems for THSR operation. As a result, improvements by reducing train speed are not feasible.
3. Trainset accumulated mileages  
From experimental results, when temperature falls from group T1 to T3, it is very likely that alarms occur due to train sets belonging to group M3, M4 and M5. Therefore, when trainset accumulated mileages reach near M3, whirling can be implemented to maintain wheel roundness and improve the number of BIDS alarms.
4. Alarming location  
From experimental results, when temperature falls in group T3, it is very likely that alarms occur due to train sets belonging to group L4 and L5. Therefore, due to maintenance on railroad in specific locations, improvement can be made. However, improvement implementation can be made for group T3 only. When temperature falls in group T1 and T2, it is impossible to reduce the number of BIDS alarms. As a result, improvement for alarming location is still very limited.  
Based on the above analysis, it can be inferred that when train accumulated mileages reaches near M3, whirling operation can be implemented to reduce BIDS alarms. On the other hand, this takes only maintenance into consideration. Timing of whirling operation can also be a new study topic. Based on experiment results, when temperature falls in group T4 and T5, it is very unlikely for BIDS alarms to occur. Therefore, whirling operation implemented in these periods of time does not only benefit THSR much but is also a waste of maintenance workforce and costs. Note that when temperature reaches near group T3 to group T1, the number of BIDS alarms increases; as a result, timing of whirling operation can be made set to when temperature falls within these three groups.  
Based on this study, it can be inferred that when temperature falls from group T1 to group T3, and accumulated mileages reach near M3 where trainset wheels can be whirled, the number of BIDS alarms is reduced.