These sort of machines are supposed to have dead man switches that require a certain level of force to keep them going. This is to prevent the vehicle from careening on if the driver has a heart attack or becomes unconscious. However, the drivers hate these (because they are tiring to use due to the constant force required), so they get their unions to pressure the operators to reduce the required pressure. The end result is that a fat nigger can operate it with just the weight of her larditous arm. Dumb nigger falls asleep and the train keeps on "truckin'".