Final answer:
For a child in a rear-facing car seat, harness straps should be at or below the child's shoulders to appropriately distribute forces and minimize injury risk during a crash.
Step-by-step explanation:
When securing a child in a rear-facing car seat, it's essential for safety that the harness straps are positioned at or below the child's shoulders. This ensures that in the event of a crash, the forces are better distributed across the child's body, minimizing the risk of injury. The straps should be snug, with no slack, to hold the child firmly in place. Pediatric safety guidelines often emphasize this point as part of a comprehensive approach to infant safety in vehicles.