Mass transit passenger vehicle seat and mass transit passenger vehicle comprising such a seat

This mass transit passenger vehicle seat (2) comprises a seat bottom (4). It also comprises a fall prevention device (6) placed on the side (C1) of the seat bottom (4) and translatable in a globally vertical position (Z6) perpendicular to the seat bottom between a first configuration (figure 1), where it is completely integrated into the seat bottom, and a second configuration (figure 2), where it protrudes above the seat bottom.