A protection system for motorized pedestrian access passageways, comprising a mechanism for the closing or opening of said passageways, suitable for activating at least one sliding and oscillating shutter (12), which emerges from and re-enters, respectively, the interior of at least one seat (25) of a shaped structure positioned to the side of the access passageway; the shutter (12) is fixed to a longitudinal covering strip (17) which is thus entrained along the seat (25), by means of side guides (9, 10), so as to inhibit access to the seat (25) when the shutter (12) is in a position which closes the passageway.