At what age must a child be fastened in a safety seat?

A child must be fastened in a safety seat when they are under 4 years old. This requirement is grounded in safety regulations aimed at minimizing the risk of injury during car travel, as younger children are more vulnerable due to their size and physical development. Safety seats are designed to securely hold a child in place and provide essential protection in the event of a collision.

While the other age limits mentioned in the other choices may seem relevant, they do not accurately reflect the specific legal requirements in Wisconsin regarding when a child must be in a safety seat. For example, the age of 2 years old mentioned in the first choice only covers a portion of the regulations and does not align with the broader scope of child safety seats, which extends up to 4 years old. Choices mentioning the ages of 8 or 12 years refer to other stages of child restraint requirements but do not pertain specifically to the initial safety seat requirement. Thus, the most accurate and contextually appropriate answer is that children must be fastened in a safety seat until they are 4 years old.