Systems for reminding a driver when height extending cargo is loaded on a vehicle. The warning systems can include an indicator that is selectively moveable between a warning position and a prevention position. In the warning position, the indicator is in a driver's field of vision. In the prevention position, the indicator at least partially obstructs cargo from being loaded on the vehicle. The indicator can be moved from the warning position to a prevention position by an arm, which can be designed to extend and retract.