Not at anywhere near the speeds or volume that they’re used by cars today

You've moved the goalposts. You previously said streets aren't for cars. Now you're fine with cars, but its the volume/speed you take issue with? The article you're replying to had a car driving at 17mph before the kid ran in front of it. A horse drawn carriage can go about twice that fast at top speed.

Streets used to be legitimate and safe places where kids could play or people could walk.

You...actually think that there weren't people injured and killed by horse carts long before cars existed? Are you serious? I'm beginning to think you have no idea what you're talking about especially with regard to history.