Example vehicle restraints having example anti-rotation features are disclosed herein. In some examples, an actuator in the form of a hydraulic cylinder moves both a vehicle barrier and its brace between stored and activated positions. If the vehicle pushes the barrier from an upper blocking position to an intermediate blocking position, the brace helps support the barrier at the intermediate blocking position to prevent the vehicle from further pushing the barrier to its stored position. To avoid damaging a cover plate or other relatively weak areas of a vehicle's RIG (rear impact guard), some example barriers disclosed herein exert a holding force that is less at the upper blocking position than at the intermediate blocking position.