@mott555 Farm tractors are not easy things to stop for anyone but the driver. Their large tires and the torque that the engine applies to the wheels allow them to climb over most types of barriers. It's dangerous to try to get onto one while it's moving, because the weight and unstoppability will result in one's serious injury or death if one fails to board and gets run over instead. If it has a PTO shaft on the back, then there's yet another thing that needs to be avoided, because that's direct power from the engine, and it won't stop until the engine does.
I'm going to choose to assume that this was posted for the benefit of others, and was not an attempt to educate a farmboy like me on how tractors work.