Promoting rail transport is one of the most effective ways of combating climate change and reducing the carbon footprint. This has naturally led to increased demands on rail transport to enhance track capacity by increasing travel velocity, the number of trains, and axle loads. Track design usually considers the critical velocity of the moving force as a safety limit. This velocity is equal to the lowest wave propagation velocity in the supporting structure, resulting from the dynamic interaction of all its components. It is tacitly assumed that other aspects, such as instability of the moving inertial object, can only occur in the supercritical velocity range, and therefore do not affect this safety limit. This contribution aims to show that these considerations are not as straightforward as they may appear. In particular, analyses of instability typically consider a single contact point with the structure, leading to conclusions regarding its relation to the critical velocity. Therefore, the first part presents and justifies the analysis of situations in which instability can occur in the subcritical velocity range, showing that a necessary condition is the consideration of two proximate contact points to activate dynamic interaction [1]. The second part of this contribution demonstrates that the critical velocity does not necessarily represent a limitation for moving loads. By tailoring the parameters of a three-layer model, the lowest critical velocity can be adjusted to a hardly noticeable pseudocritical velocity, which does not impose a limitation on moving loads [2].