The study of train-track interaction and resulting ground vibrations generally (and often exclusively) focuses on the vertical direction. This study explores the directional characteristics of train-induced ground vibration, based on in-situ measurements conducted at different locations in the Netherlands with two subsoil types - sand and clay, and different substructures, for a set of operational parameters. Triaxial accelerometers were installed at the ground surface along the track, in a spatial configuration capturing both near-field (or non-radiating) and far-field (or radiating) contributions of the ground response in terms of particle motion. Through statistical and comparative analyses of field-measured data, the results show a strong dependence of the dominating directions of particle motion on the ground composition (soft or still soils) and therefore also on the cross-sectional track geometry in terms of substructure and embankment. These findings highlight the relevance of paying due attention to both normal and in-plane (longitudinal and lateral) components of train-track interaction and ground particle motion in the modeling, mitigation and prediction of train-induced vibration hindrance.