Troubling signs

I don't understand the signs posted on freeway overpasses that show the clearance height to oncoming truckers. You know the ones that say, "Truck 14 Feet?" I can just imagine a trucker humming along at 70 miles per hour, looking up to see a sign telling him that his semi is too tall for the overpass he's about to go under. What his option at this point? It's like they're giving the truckers just enough time to duck and pray.

I'm amused by signs that say, "For Sale By Owner." Isn't it implied that whoever's selling the item is the owner? What's the alternative to this - "For Sale By Shady Roommate?"

I took a CPR class and learned that when you're choking you're supposed to put your hands up to your throat. This "international choking sign" is supposed to indicate that you need the Heimlich maneuver. I also learned that when you perform the Heimlich on someone, you'll most likely break their ribs. This all makes me very nervous. People naturally put their hands to their throat whenever they're having trouble swallowing, even if they aren't in a life-or-death situation. I think that there should be an additional sign that a person can use if they are really in danger of choking - like a "twig snapping" motion followed by a "thumbs up." That way I can jump right in and start crackin' their ribs like a dump truck running over a pile of walnuts (while saving their life, of course).