## 3 Correct Direction of Chinese HSRS Improved Design  
### Rational Condition of Wheel-Rail Matching  
In view of the particularities of Chinese HSR practices, i.e., the back-to-back distance of wheelest, \(L=1353\) mm, and the improper ratio of curve to tangent in route planning on dedicated lines, the rational condition of wheel-rail matching should be as follows: the nominal equivalent conicity \(0.10\geq\lambda_{eN}>\lambda_{emin}\), and the minimum allowable equivalent conicity \(\lambda_{emin}=\) (0.03-0.06). This rational condition can be determined by referring to relevant experiences at home and abroad. Although bogie articulated and car body tilted are two key technologies for speeding up on the present European rails, the rail grinding treatment is one of the important preconditions for their implementation. For the practices of Japanese Shinkansen or speeding up on the present European rails, although the bottom inclinations are different, but \(L=1360\) mm in general. When the wheel standard profile S1002 is matched to UIC rail 60E1 with a bottom inclination of \(1/20\), \(\lambda_{eN}=0.01\). However, as shown in Figure 3a,b,d, the tight track gauge or narrow track window is formed between them, the negative influences of which are eliminated by rail grinding or wheel renewal profiles. Figure 2: Flow chart of large-scale MDO such as HSRS by using dynamic design methodology. Relatively speaking, the operation and maintenance practices of French TGV/AGV trains have a more appropriate technical economy, and the survey of service lines shows two areas with a relative higher probability distribution density of low and high track conicity [39]. These are closely related to the techniques of articulated bogies and longitudinal damping between inter-vehicles. The articulated bogies have a 3 m wheelbase and are configured with 2 anti-yaw dampers per bogie to ensure the stability performance of bogies at higher equivalent conicity. Meanwhile, there are four longitudinal dampers installed in the upper and bottom parts between inter-vehicles to remove and eliminate the car body instability at lower equivalent conicity. For the dedicated lines with a speed grade \(\geq\) 230 km/h [39], there are two extreme cases as follows:  
(1) Italian ETR600 train requires that the track conicity after rail grinding be less than 0.05, tries to achieve the expected goal of uniform wear stage at an extraordinary cost, and the maximum speed can reach 300 km/h in mountain lines. After the acquisition of tilting techniques from FIAT, the first ETR 600 tilting train launched by ALSTOM switched to traditional anti-yaw dampers, i.e., the mechanism of large damping to suppress hunting. However, an active control technique of lateral and roll integrated suspension may be developed when considering the car body instability that occurred occasionally at low conicity [40]. (2) German ICE3 train requires that the occurrence probability of track conicity 0.10, 0.20, and 0.30 is 50%, 95%, and 99%, respectively. However, the rail grinding treatment unexpectedly acquires the stable wear stage at a high conicity of \(\lambda_{e}\) = (0.25-0.35), and the period of wheelset re-profiling under the floor is extended to (35-45) \(\times\) 10\({}^{4}\) km [39]. The general regulations presented in the wear survey of worldwide wheel-rail contact are as follows: wheel hollow tread and railroad top crown, i.e., curvature radius is varied from 350 mm to 150 mm [41]. The radical reason for implementing one kind of wheel-rail matching or the other is often institutional inertia--a strong tendency to continue doing what has been completed in the past. But the impacts of wheel and rail profiles on the  
Figure 3: Influences of track parameters on low wear area of wheel-rail contact and detrimental wear evolution. (**a**) Two-point contact problem on rail shoulder at one side of gauge corner such as flange root and side wear. (**b**) Comparison of three typical wheel-rail matching situations for contact point variation on railroad.