孩子坐车用哪种座椅按年龄分四段：后向尽量坐久、坐后排到13岁
孩子乘车时用哪种座椅，不是看家长方便，而是按年龄和身材分四段推进。美国疾病控制与预防中心（CDC）的儿童乘车安全指引说，每一段都要坐到孩子达到该座椅的身高或体重上限再换下一段，并强调一个总原则：13岁前，孩子都应系好安全约束坐在后排。
第一段是后向安全座椅，从出生用到大约2到4岁。用安全带式约束（harness）把孩子固定在后向座椅里，尽量坐久，直到达到座椅标注的最高身高或体重上限；后向座椅绝不能放在前排，因为前排乘客安全气囊在碰撞中弹出可能重伤甚至杀死幼儿。
第二段是前向安全座椅。孩子长大坐不下后向座椅后，改坐带约束带和顶部系带（top tether）的前向座椅，同样坐在后排，至少用到5岁，并一直用到达到座椅上限为止。
第三段是增高坐垫（booster seat)。孩子坐不下前向座椅后，在后排用增高坐垫，直到汽车安全带不靠坐垫也能贴合身体。安全带真正贴合通常发生在9到12岁：腰带应横过髋部上方的大腿（不是肚子），肩带应横过肩膀和胸口中央（不是脖子、脸，也不能滑下肩膀）。
第四段才是直接系安全带。在此之前不要急着「毕业」：CDC 提醒，各段推荐年龄会因孩子生长速度和不同座椅的限值而不同，判断换段的标准应以座椅说明书上的身高体重上限为准，而不是年龄到了就换。（来源：美国疾病控制与预防中心）
Four Stages of Child Passenger Safety: Rear-Facing as Long as Possible, Back Seat Until Age 13
Which seat a child should ride in is decided by age and size, in four stages, according to the U.S. Centers for Disease Control and Prevention (CDC). Each stage lasts until the child reaches the seat's maximum height or weight limit, and one rule runs through all of them: keep children properly buckled in the back seat until age 13.
Stage one is a rear-facing car seat, used from birth until roughly age 2 to 4. Children should ride rear-facing, buckled in a harness, as long as possible, until they reach the car seat's maximum weight or height limit. A rear-facing seat must never be placed in the front seat, because front passenger air bags can injure or kill young children in a crash.
Stage two is a forward-facing car seat with a harness and top tether, in the back seat. Children move to it after outgrowing the rear-facing seat, and should stay in it until at least age 5 and until they reach that seat's limits.
Stage three is a booster seat, again in the back seat, used after outgrowing the forward-facing seat and until the vehicle's seat belt fits properly without a booster. Proper fit usually occurs between ages 9 and 12: the lap belt must lie across the upper thighs, not the stomach, and the shoulder belt across the center of the shoulder and chest, not the neck or face and not off the shoulder.
Only then does a child graduate to a seat belt alone. The CDC notes that recommended age ranges vary with children's growth and with each seat's limits, so the manual's height and weight limits, not a birthday, should decide when to move up a stage. (Source: U.S. Centers for Disease Control and Prevention)
来源：美国疾病控制与预防中心
发布：GSM·美国（发布链接）
图片来源：图：两名幼儿坐在汽车安全座椅里。Wikimedia Commons 图片（公共领域）。 / Photo: Two young children buckled into car seats. Image via Wikimedia Commons (public domain).
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