Abstract: A security device (2) is described for protection access to and from a parking space by being suitable for secure mounting to the entrance/exit of the parking space at ground level comprising a barrier or sign (9) capable of movement between a raised position for preventing movement of a vehicle past the barrier (9) and a lowered position permitting the vehicle to be driven over the device (2), and arming pedal (4) which is depressed when the vehicle is driven over the device (2) to energize a driving means in the form of a torsion spring (78) which is connected via a control means including a cam (40) having two cam lobes (42,44) for effecting movement of a bar (60), to the barrier (9) by a suitable connection means, such as for example a slotted wheel (84) and pulley arrangement, so that operation of the control means causes lower or raising of the barrier.