This is fun. Interesting analysis. A few quick thoughts: Why the focus on Jerk/Volatility instead of Acceleration/Force? The energy imparted to the passengers

This is fun. Interesting analysis. A few quick thoughts: Why the focus on Jerk/Volatility instead of Acceleration/Force? The energy imparted to the passengers is proportional to the forces. Is there any reason to suppose that Jerk is more important to the experience of discomfort (or mechanical wear for that matter)? The analysis notes that the distribution is not normal, but it does not explore the what the underlying distribution might be instead. Given that the train's velocity is constantly accelerating/decelerating it seems unlikely that it would be a single distribution. However it may be the case that the observed variations are the result of a superposition of normal distributions. A Fourier transform could maybe helpful to explore these aspects.