At about 9:10 a.m., the tiller ladder truck was conducting a routine check and was making a right turn from Mission Street onto New Montgomery Street when it struck the parked Penske big-rig, fire department spokeswoman Mindy Talmadge said.
After being struck, the big-rig hit the 20-year-old operator of the truck who was on the sidewalk behind the passenger side door, Talmadge said.
The man fell to the ground but was alert and talking. He had minor complaints of pain and was transported to San Francisco General Hospital, according to Talmadge.
The accident is being considered industrial and the California Division of Occupational Safety and Health has been notified and will be investigating.