A barrier (1) for controlling the transit of vehicles, comprising a supporting frame (2) for a bar (4) for blocking the passage of vehicles, the blocking bar being movable, following the actuation of first motor means (5), with respect to the supporting frame (2) about a first pivoting axis (100) which is substantially parallel to the direction of travel (200) of the vehicles that cross the barrier (1) in order to move between a blocking position, in which the blocking bar (4) is arranged substantially transversely to the direction of travel (200) of the vehicles, and a passage position, in which the blocking bar (4) is arranged laterally with respect to said direction of travel (200) of the vehicles, the blocking bar (4) being movable, following the impact of a vehicle, about a second pivoting axis (101) which is substantially perpendicular to the direction of travel (200) of the vehicles and to the direction of longitudinal extension (201) of the blocking bar (4) in order to move, in contrast to the action of elastic means (6), from an active condition, in which the blocking bar (4) is arranged on a plane which is substantially perpendicular to the direction of travel (200) of the vehicles, to an at least partially broken through condition; the barrier (1) furthermore comprises means (7) for locking the rotation of the blocking bar (4) about the second pivoting axis (101) which are adapted to prevent the passage, owing to the action of the elastic means, of the blocking bar (4) from the at least partially broken through condition to the active condition, the locking means (7) being able to be deactivated on command to allow the passage of the blocking bar (4) from the at least partially broken through condition to the active condition.