Abstract: At 8:15 a.m. on August 17, 2017, an employee was in a Hyster Model R30XMS3 Narrow Aisle Order Picker putting stock away on the outside of the aisle (Aisle #1). The employee was 16 feet high and protected from falling through the use of a personal fall arrest system. The employee was unable to move the order picker based on the height he was working from. The forklift was not blocking any of the perpendicular aisles. A coworker was traveling down Aisle #16 in a second Hyster Model R30XMS3 Narrow Aisle Order Picker after retrieving materials. The coworker was approximately 12 feet high while traveling at approximately 3.5 mph. The aisles are on a wire guided system. The employee was traveling with the load in front of him. The boxes were stacked as high as 6 feet 5 inches high, blocking the employee's view. The employee was honking his horn while traveling down the aisle to alert others of his presence. The employee pulled the lift out of the aisle and struck the employee's order picker, knocking it over. The employee struck furniture that was on the floor below. Paramedics were called, and the employee was taken to Shock/Trauma. The employee received a laceration to his knee and bruising to the body. The coworker is trained on forklift operation, and there is a certification record of that training. The coworker received training from a previous employer, but was never retrained when he started with his current employer.