Abstract: A security apparatus for a shopping cart or other wheeled vehicle having a plurality of casters has a braking member rotatably mounted on a wheel axle of one of the wheels. The braking member is movable between a raised position spaced above the ground surface and an operative position contacting the ground surface, and has a portion projecting radially outwardly from the outer peripheral rim of the wheel at least in the operative position so as to separate the wheel from the ground and impede movement of the vehicle. A locking device releasably locks the braking member in the raised position, and is released by a trigger device in response to a signal from a signal system extending around an area in which carts are to be retained, at which point the braking member rotates into the operative position, stopping normal movement of the cart.