Abstract: On May 22, 2013, Employee #1 of San Francisco Recreation and Parks Department sustained a head injury while conducting his duties. Employee #1 was assigned to three of the San Francisco parks including the Franklin Square, which is elevated from its surrounding sidewalks. The park perimeter lawn has slopes approximately 30 to 60 feet, 8-inch thick borders, and four foot-high retaining walls. A riding lawn mower, (Toro Groundmaster 220, 1997) had been used to cut the grass for both the flat and the sloped perimeter. The riding lawn mower was not equipped with Roll-Over Protection (ROP) and seat belt. At approximately 8:00 a.m., Employee #1 started mowing the border lawn area at the corner of Bryant and 17th Street where the lawn slopes were approximately 28.5 to 30% and bordered the 8-inch thick, four-foot high unprotected retaining wall. To start from the edge of the side, which had been blocked by a tree, he started backing up from the edge of the retaining wall when the rear right tire hit the retaining wall. Employee #1 was thrown out of the mower and landed on the sidewalk. He suffered a laceration on his head, which required 10 stitches, and a minor brain hemorrhage. The cause of the accident was using a riding lawn mower on a steeply sloped surface and within 5-feet of the unprotected retaining wall.