If I was raising my child in a big city, and she needed to learn to live and navigate through our big city, yes, I would let her start riding the subway around 9. It's like a small town kid walking down the block to the convenience store to buy a bag of candy. If I was raising my kid as the above mentioned small town kid, no, she wouldn't get to ride the subway on her own at 9. I'd wait until she was in high school, after having been to the city with me many many times. Kids raised in different types of places learn different survival skills. A country kid would be lost in a subway system. Heck, a country grown-up would get lost on a subway system! As for staying home alone, 9 or 10 also seems reasonable to me, for 2-3 hours at a time, and when they're awake. I wouldn't leave a sleeping child alone. Not until they're older. A 9 year old would be too disoriented should she wake up to a fire alarm, alone, at midnight. But, then again, it all depends on your child's ability to be independent, and feel comfortable with it. I was left alone in the afternoons starting around 10 and was fine, but didn't want to be left alone at night until I was 12. It's that whole dialogue with your kid thing. It's as much up to them as it is up to you.