Around these parts, that and about $1.50 will get you a cup of coffee. Most people revel in their ignorance and would rather nit-pick symantics of posting.
By in large, I find Americans to be dumb and arrogant. Well, I'm one of them ... probably right up to and including my own complaint. ;-D
My "gut feeling" is that it probably takes more than twice as much space to stop if you double the vehicle's speed.