Based on a choice experiment conducted in the Rhône-Alpes Region, this paper estimates an Integrated Choice and Latent Variable model which addresses the heterogeneity of values of time. We evaluate how sensitivity to travel time by public transport is distributed along with level of comfort. Comfort is modeled as a function of objective attributes and individual perceptions about it : whether a seat is guaranteed, quality of trip experience (experienced feelings), (perceived) use of travel time during the trip, and overall ease of using public transport (perceived behavioral control). The results show that the two latter ones play a significant role in the choice of a public transport mode and that the value of time function is downward sloping with higher levels of objective and perceived comfort. We discuss public policy implications by means of simulated scenarios.