Despite the use of automatic backing-up warning systems, large mobile equipment is still involved in reversing collisions, causing injuries, fatalities, and property damage. This paper discusses specific human factors that contribute to the failure of this type of system as used on front-end loaders in the surface mining industry. The use of the backing-up automatic alarm causes the operators to lose the perception of responsibility for vigilant behavior, while the ground crew predictably becomes habituated to the alarm. These human factors and their interaction with the noise pollution created by the alarms sets up a potentially unsafe condition. U.S. Bureau of Mines research into discriminating backup warning systems could provide an effective alternative to the conventional backup alarm.