## 4 Next Generation HSRS with Higher Speed
### Comprehensive Assessment of Safety and Stability  
By using three different wheel profile designs and the lateral span variations of nominal rolling circles, as shown in Table 2, eight different conditions are constructed for wheel-rail matching. The comprehensive assessment of safety and stability shows that when \(\lambda_{e}\) < 0.10, as shown in Figure 12, the hunting motion stabilization will be maintained with  
Figure 11: Semi-active damping solutions between inter-vehicles and associated technical implementation. (**a**) Motor-trailer-motor trainset with relevant parameters. (**b**) Cracks occur on lower part of outer windshield at both sides. (**c**) Semi-active damping implementation with stiffness and damping in lateral and vertical directions per constraint point. (**d**) Principles of pneumatic technique when activated or inactivated.  
the hypothesis of small creepge and non-spin, which is a sufficient and necessary condition for the formation of the uniform wear stage at low conicity.  
However, when \(\lambda_{e}\) = 0.10/0.16, the hunting motion stabilization is transformed into instability hunting oscillation. For the motor vehicle, according to UIC518 or UIC14363, the maximum speed is allowed to 555/530 km/h. Meanwhile, for trailer vehicles, the maximum speed can be increased to 650/600 km/h if the safety threshold value is set to 1.5 g. So, the self-adaptive improved design of higher speed bogies is able to break the worldwide HSR record of 575 km/h when \(0.03<\lambda_{e}\leq 0.15\). Considering the normal wear of wheel-rail contact and associated effects of tight track gauge, when \(\lambda_{e}\) = (0.20-0.35), there is little room for promoting the safety speed.  
For this reason, the rail experts are reminded that the occurrence probabilities of track conicity (0.03-0.10), 0.25, and 0.35 should be controlled with 85%, 95%, and 99%,  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Wheel Profile** & **Lateral Span between** & **Equivalent** & **Max. Speed for** & **Max. Speed for** & **Remarks** \\
**Typical** & **Nominal Rolling** & **Circles/mm** & **Criticality/\(\lambda_{e}\)** & **Moor** & **Trailer** & **Remarks** \\  & & & & & Vehicles/(km/h) & \\ \hline XP5S & 1493 & 0.06 & 790 & 740 & When \(\geq\) 200 km/h and \(\lambda_{e}\) < 0.10, safety speeds & under hunting motion stabilization are \\ LM & 1472 & 0.08 & 765 & — & determined by maximum wheel unloading rate. \\ LM & 1493 & 0.10 & 555 & 650 & For motor vehicle, safety speeds are determined \\ S1002G & 1500 & 0.16 & 530 & 600 & as required in UIC518 or EN1463, but for trailer, \\ S1002G & 1504.3 & 0.20 & 435 & 480 & safety speeds are decided by concept of limit \\  & & & & & speed. i.e., safety threshold of lateral acceleration \\ S1002G & 1506.1 & 0.25 & 405 & 420 & of bogie frames can be increased to ca. 1.5 g. \\ S1002G & 1506.8 & 0.30 & 390 & 390 & Safety speeds are determined as required in \\ S1002G & 1507.2 & 0.35 & 380 & 380 & UIC518 or EN14363. \\ \hline \hline \end{tabular}
\end{table}
Table 2: Influence of actual equivalent conicity on limit speeds of motor and trailer vehicles.  
Figure 12: Safety and stability assessments of self-adaptive improved motor and trailer vehicles. (**a,b**) Evaluations of safe speed space of motor vehicle and associated lateral acceleration of bogie frame based on UIC518 or EN14363. (**c,d**) Evaluations of safe speed space of trailer vehicle and associated lateral acceleration of bogie frame according to concept of limit speed.  
respectively, i.e., the occurrence probability of track conicity (0.25-0.35) is required to be less than 5%.