Abstract: A parallelogram gate for controlling traffic on a roadway, comprised of an arm assembly that is rotatable between a raised position and a horizontal, longitudinally-extended, roadway blocking position, a housing, and a drive assembly mounted within the housing. The arm assembly has parallel, elongated upper and lower rails, and a plurality of spaced-apart pickets pivotally attached to the upper and lower rails. A stationary pivot attaches a pivot end of the upper rail to the housing. A pair of vertical, grooved channel guides are attached to the housing at a location within the housing that is intermediate the stationary pivot and a lower portion of the housing. The drive assembly includes a hydraulic cylinder having a vertically-upward directed piston arm and mounted to the lower portion of the housing. A horizontal pin inserted through a traveling clevis carried by the piston arm, and inserted through a pivot end of the lower rail, extends into a groove within each of the guides.