# Review on Rail Damage Detection Technologies for High-Speed Trains
## 4 Railway Non-Destructive Testing Platforms and Equipment
### Comparison and Discussion of Platform Characteristics for Four Detection Methods  
Different rail inspection methods and platform equipment can achieve the non-destructive testing of rails to a certain extent. Table 1 shows a comparative analysis of the characteristics of the summarized rail inspection methods and platform equipment. From Table 1, it can be seen that different detection methods and platform equipment have their own advantages and disadvantages. Suitable detection methods and equipment can be selected according to specific rail conditions. Electromagnetic detection methods have relatively deep development and application in theoretical research and technical application. Currently, they mainly focus on the quantitative analysis and research of rail defect detection, as well as the formulation of detection standards, including rail surface quality detection under multi-physical field coupling. However, they have certain \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Serial** & **Testing Methods** & **Detection** & **Advantages** & **Disadvantages** & **Digital Twin and Life Prediction** & **Normal Testing Pass Rate** \\ \hline \multirow{2}{*}{1} & Manual detection methods & Viewing with human eyes & Direct judgment of defects & Defects are easily missed, fatigue, and low efficiency & NO & (depending on testing experience) \\ \hline \multirow{2}{*}{2} & Ultrasonic & Ultrasonic & Long detection distance and high accuracy & Poor noise resistance and inability to reflect defect types & NO & 85–95\% (internal defects) \\ \hline \multirow{2}{*}{3} & Eddy current testing methods & Eddy current effect & High detection accuracy & Low signal-to-noise ratio and low anti-interference ability & NO & 80–90\% (surface/near-surface defects) \\ \hline \multirow{2}{*}{4} & Laser vision inspection methods & Image recognition & Non-contact and high precision & Internal defects cannot be detected & NO & 85–95\% (visible surface defects) \\ \hline \multirow{2}{*}{5} & Infrared thermal sensing & Infrared thermal sensing image recognition & Non-contact and high precision & Poor noise resistance and inability to reflect defect types & NO & 70–80\% (thermal anomaly defects) \\ \hline \multirow{2}{*}{6} & LiDAR detection methods & Electromagnetic energy pulse detection & Non-contact and high precision & High cost and inability to reflect defect types & NO & 90–95\% (geometric damage) \\ \hline \multirow{2}{*}{7} & Terahertz detection methods & Terahertz time-domain spectroscopy & Non-contact and high precision & High cost and limited detection thickness & NO & 60–80\% \\ \hline \multirow{2}{*}{8} & Hand-pushed track inspection & Manual pushing and multi-sensor fusion & Small size, light weight and easy to install & Low efficiency and slow detection speed & NO & 95–98\% (comprehensive testing) \\ \hline \multirow{2}{*}{9} & Active track inspection car & Automatic multi-sensor fusion & Autonomous detection and high efficiency & Low battery life & NO & (comprehensive testing) \\ \hline \multirow{2}{*}{10} & Rail inspection robot & Active multi-sensor fusion & Large detection angle and high accuracy & Unable to be controlled remotely and high cost & NO & 95–98\% (comprehensive testing) \\ \hline \multirow{2}{*}{11} & Vehicle-mounted track inspection vehicle & Active multi-sensor fusion & Large detection angle and high accuracy & Unable to be controlled remotely and high cost & NO & 95–98\% (comprehensive testing) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of detection characteristics. Figure 20: On-board rail inspection vehicle. limitations and cannot accurately judge the rail life. Machine visual inspection methods based on image processing technology have solved the problem of low accuracy in rail surface quality inspection to a certain extent, and non-contact detection methods have also become a hot research topic.