Experimental evidence, as obtained from line tests, shows that, under some circumstances, the level of hunting motion experienced by a railway vehicle negotiating a curve can be higher than for the same vehicle running at the same speed on tangent track. Starting from this experimental observation, this paper aims to propose a physical explanation for the different hunting behaviour of a railway vehicle running in a curve. After presenting the available experimental evidence, a qualitative examination of the phenomenon is provided. A multi-body model of the vehicle running in a curve is defined and validated against line measurements. This model is then used to numerically evaluate the hunting behaviour of the vehicle in a wide range of curve radii relevant for high-speed lines. In this way, the experimental findings are extended to curve radius and cant deficiency values that were not observed in line tests, due to the use of a specific track section and to the range of speeds covered by the tests.