Abstract: A motorized bar barrier device, including a shaft (14) supporting the bar, a motor unit (12) for the rotation of the shaft and a unit (13) for offsetting the moment produced on the shaft by the weight of the bar. The offsetting unit (13) comprises a torsion spring (24) wrapped coaxially at the shaft and which has a first end (27) that is pushed by the rotation of the shaft to wind the spring when the shaft (14) is turned in a first direction starting from a neutral position and a second end (28) that is pushed by the rotation of the shaft to wind the spring when the shaft (14) is turned in a second opposite direction starting from the neutral position. This way, the system can provide offsetting of the moment produced by the weight of the bar in both the directions of rotation starting from the neutral position.