Lockout/tagout is an important safety procedure to prevent accidental movement or operation of machinery and electrical equipment when it might endanger workers. Under lockout procedures, the machinery is completely shut down and padlocks or other safeguards are implemented to keep the equipment from being activated. To further prevent accidental turn on, a "Do Not Start" sign is mounted on the controls. In a study of accidental death caused by failure to observe lockout/tagout procedures, OSHA found that accidents happened most often with moving machinery, electrical equipment, and vehicles. The four basic causes of these deaths were: failure to deactivate machinery, accidental activation, equipment failure or malfunction, and inadequately followed or not at all followed lockout/tagout procedures.