# The Influence of Track Irregularity in Front of the Turnout on the Dynamic Performance of Vehicles
## 5 Conclusions and Future Works  
In this paper, the effects of three irregularities in front of turnout with the alignment, longitudinal level, and cross level on the dynamic performance of vehicles are studied. The results of this paper will be helpful for understanding the relationship between track irregularities in front of the incoming turnout and running performances of high-speed trains. The wavelengths and amplitudes of the irregularities considered in this paper are referenced from the Chinese standards for track irregularities and the observed track irregularity characteristics of high-speed railway lines. Due to regular repairs and maintenance on high-speed railways, the amplitudes actually observed on high-speed railway lines rarely exceed the values considered in the simulation study. The results obtained in the ranges of amplitudes and wavelengths considered in this study can be summarized as follows.  
1. The alignment irregularity in front of the turnout mainly affects the wheelset lateral force and lateral acceleration of the vehicle body; the irregularity of the longitudinal level in front of the turnout mainly affects the wheel-rail vertical force, wheel unloading rate, and vertical acceleration of vehicle body, and the irregularities of the cross level in front of the turnout mainly affect the wheel unloading rate and lateral acceleration of the vehicle body.
2. The dynamic performance of the vehicle is most sensitive to short-wavelength irregularities in front of the turnout. Short wavelength irregularities are more likely to cause a greater wheel-rail force and wheel load reduction, resulting in a greater safety risk. Thus, special attention should be given to short-wavelength irregularities in front of the turnout during maintenance.
3. Another interesting aspect is that the alignment irregularity with a long wavelength (40 m) has a significant effect on the wheelset lateral force and lateral acceleration of the vehicle body, which is caused by the two-point contact between the wheel and rail.
4. The frequency range of the effect of the irregularities in front of the turnout on the wheel-rail force, safety indicators, and accelerations of the vehicle are mainly below 200 Hz, 50 Hz, and 20 Hz, respectively, according to the frequency analysis.
5. The comprehensive assessment of different irregularities in front of the turnout from time-frequency analysis represents a quantitative and intuitive reflection of the effect of the irregularity on the dynamic indicators, which provide a reference for maintenance.  
In future research, the influence of track irregularities in front of the turnout on the dynamic performance of a vehicle when passing through the turnout on the sideway and from the crossing panel to the switch panel should be further studied. The analysis can also be carried out in combination with included lines, curve lines, and different positions of the irregularity in front of the turnout.  
W.C.: conceptualization, software, methodology, writing--original draft, and writing--review and editing; X.C.: conceptualization, supervision, and writing--review and editing; Q.W.: software and writing--review and editing; X.T.: software and writing--review and editing; J.S.: writing--review and editing; F.Y.: writing--review and editing. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China, grant number 51778050, 52178405, and the Fundamental Research Funds for the Central Universities, grant number 2018 JBZ003, 2020 JBZD013.  
Not applicable.  
Data Availability Statement: Data are contained within the article.  
The authors declare no conflict of interest.