I think what @fritz is getting at is this trend (conspicuously, at least, in the US) toward more and bigger cars and trucks. I'm 41, and I grew up on a cul-de-sac street where all the kids played by ourselves outside until the street lights came on. That was my experience. My parents never seemed to have a worry that we'd take care of ourselves and come home for dinner.

But today, even in that same neighborhood (which we moved away from when I was 10), there are many more cars, and the rise of the pickup truck and SUV has created a minefield for kids. The drivers of most pickup trucks in the US couldn't see a five-year-old who is less than about 10 feet from the hood. You see parents buying trucks and SUVs because they consider them safer, which is true in the sense that we're in a battle of who can drive the biggest, heaviest truck. But to pedestrians, they're fatal. If you're struck by a car, you roll over it. If you're struck by a pickup truck, it rolls over you.

The truck problem is mainly regulatory, and it bothers me personally only because I know that the Ford F-150 is the most-sold vehicle in America, and that some 70% of those truck owners don't use them to haul anything, ever. Now I have a five-year-old son, and we live on a sort of main road in town, and we're hesitant to let our kid play even in the front yard of our own house. Last year, a distracted driver failed to follow the curve of our street two doors down from us, chopped a telephone pole in half, crashed into a tree and their car caught on fire.

My kid's bus stop is at a crosswalk on our street, and drivers don't even slow down for it, even with a bunch of kids and their parents standing there. Something culturally has changed with how drivers behave. We are auto-centric here, and we design our towns and cities to strongly broadcast that.