They nick surface skin. They don't sever arteries like a straight razor could. They don't accidentally slice your jugular. A safety treadmill would--instead of

They nick surface skin. They don't sever arteries like a straight razor could. They don't accidentally slice your jugular. A safety treadmill would--instead of sucking a child underneath and pinning them--give them a friction burn or pinch their arm. It's a guard. Add a guard around the roller and you eliminate this scenario.