Answer: First, when placing the steel coil vertically, the contact area with the vehicle floor is smaller and the pressure on the floor is greater. This will be dangerous if it exceeds the maximum allowable load on the container floor.
Second, placing it vertically will cause the steel core to easily roll forward due to inertia or centrifugal force (when the vehicle stops suddenly or turns), causing danger to the driver as well as other road users, which has happened many times in reality.
Based on common reasoning, it can be seen that if the steel core is placed horizontally, the above two problems are considered solved because at that time the contact area with the vehicle floor will be the largest, causing the pressure on the floor to be the smallest, at the same time the horizontal iron core cannot roll far when encountering problems on the road or during transportation.