15 items or less does not mean 2 carts

I am an employee at a local grocery store, and for one I hate working express lanes. Why you may ask, because people are dumb and don't know how to read the big green sign that clearly states 15 ITEMS OR LESS! Really people it is right above you, some of you almost hit your head on it, but still remain completely oblivious or just pretend too. Oh and then when people see the sign and simply come in anyways, what do you think, you're special and get special treatment? Some of you may think oh he's just being lazy or maybe he's a disgruntled employee............ No it has nothing to do with that, I started there at 14 and have had to work my ass off and put up with so many rude and bitchy people to get where I am today. Anyways, I understand you are the customer and I basically have to take you, regardless you read the sign or not, but it doesn't help when I do take you and then customers behind you with 15 items or less ( who can obviously read) are all pissy with me, or when other lanes that are not 15 items or less are all clearly open and you come to me because I am closest, seriously.... walking 5 more steps ain't gonna kill ya. Ooooh and it really just boils my clams when I do decide to be nice and take a customer with a lot more than 15 items and then they are completely rude the whole time.....wtf? Didn't I just do you a favor, would it kill you to show some common courtesy, or to at least say "Thank you I did find what I was looking for," or a simple hi would suffice. Ugh seriously I wonder how I was able to work through 4 years there and still am..... seriously people A sign that says 15 Items or Less means 15 Items or Less. It's not a hard concept to grasp!