Integrating children into space conception is a growing concern in the scientific and urban planning community. In this communication, I suggest studying uses in a particular public space: the train. It brings issues of time and space use by users often forgotten by scientific research and transportation operators. Scientific literature about travel time use in trains has mostly focused on time use on commute and professional travel. While the analysis on time use during leisure travel is growing, children are only considered through activities such as « entertaining children » (Lyons et Urry, 2005). Research about parental attitudes during long-distance travel is emerging (Price and Matthews, 2013) but children's point of view is quite absent. On the other hand, literature about children's experience of mobility talks mostly about daily travel between home and school or time use in family cars (Barker, 2009). The objective of this communication is to replace children as full actors of leisure mobility aboard trains by analyzing their use and experience of travel time. My methodology is based on observations in French high-speed train and inter-city train with different service levels (low cost or not, travel time, etc.), and inspired by methods from environmental psychology (Legendre et Depeau, 2003). Systematic observations of activities and the use of space are registered every ten minutes. The children observed corresponds to age from 6 to 11. Combined with a literature review of time use typologies on trains, I try to offer a new perspective on travel time use for those unknown train passengers, children. The results of this inquiry, coupled with interviews should eventually allow to discuss issues such as "subjective experience of travel time" (Flamm, 2005).