ARCCA experts have investigated hundreds of incidents in construction zones involving numerous types of vehicles and equipment. In one case, we were asked to determine the cause of an accident where the boom of an excavator swung and hit a stand, which then toppled and caused serious injury to a bystander. Upon inspection of the excavator and an accident recreation, the ARCCA expert determined that the excavator's operator stood up to see his fellow worker on the ground who was providing direction. When he sat back down, the boom control joystick got caught in his pocket, causing the boom to swing. If appropriate machine control guarding had been in place on the excavator, this accident would not have happened.