On March 31, 2003, two Hispanic guardrail installers (the victims), ages 33 and 20, died after being struck by a section of heavy-duty guardrail that was suspended from a chain attached to the post-pulling jack of a truck-mounted post driver. A crew of six men were installing guardrail at the incident site. One of the men was seated in the rear operator station of the truck-mounted post driver and was attempting to back the truck and move the guardrail horizontally when the truck suddenly jerked and traveled backward. Coworkers positioned in front of the truck saw the truck jerk, then saw the guardrail hang up briefly on a post, flip up into the air, and strike two coworkers (the victims) who were placing bolts in a previously installed guardrail section approximately 25 to 35 feet behind the truck. The truck came to a stop in the traffic lane on the opposite side of the road. After stopping the truck, the operator used his cell phone to call 911. Emergency Medical Services (EMS) and police personnel responded within minutes. EMS personnel provided emergency care to the 20-year-old victim, who was then transported by medical helicopter to a regional trauma center where he was pronounced dead later that day. The 33-year- old victim was pronounced dead at the scene by the county coroner. NIOSH investigators concluded that, to help prevent similar occurrences, employers should: 1. ensure that equipment operators have been trained in the proper use of equipment they are assigned to operate in accordance with manufacturers' specifications and recommendations; 2. conduct a job safety analysis (JSA) to determine the appropriate equipment and standard operating procedures that should be followed when moving heavy-duty guardrail sections with mechanized equipment; 3. develop, implement, and enforce a written comprehensive safety program which includes training in hazard recognition and in the avoidance of unsafe conditions, including, but not limited to, hazards associated with working in proximity of vehicles and equipment; 4. ensure that workers who are part of a multilingual workforce comprehend instruction in safe work procedures for all tasks to which they are assigned; 5. develop and enforce a policy that requires all employees working in highway construction work zones to wear high-visibility apparel. Additionally, 1. manufacturers should clearly identify how equipment is to be used, i.e. the truck-mounted post driver is only to be used for driving and pulling posts and is not intended for other uses, such as hoisting; 2. manufacturers should explore the possibility of incorporating emergency stop switches on the rear control panel of truck-mounted post drivers. Additionally, state departments of transportation should consider requiring that contract proposals include a written comprehensive safety program that addresses safe operating procedures and worker training for all tasks to be performed under the contract, and requires that high visibility apparel be worn by all workers on highway construction jobs.