A vehicle mounted mobile container or vehicle inspection system, including: a radiation source, a movable vehicle for carrying the inspection system, and a detector arm rack which has a horizontal arm and a vertical arm, a first end of the horizontal arm is connected to the vehicle and a second end thereof is connected to an end of the vertical arm. The horizontal arm and the vertical arm are connected by a pivotal connecting device such that the vertical arm may pivot in a vertical plane, and the horizontal arm and the vertical arm may be retracted in a same horizontal plane. The novel arm rack construction may reduce the space occupied by it on top of the scanning vehicle after the arm rack is stowed so as to reduce the eight of the scanning vehicle under running condition.