A solid yellow line on your side of the road means hang out behind the big rig a little longer because the line of sight isn't quite what it needs to be to make a solid pass/no pass decision. A dotted line means go for it, but don't kill anyone or run anyone off the road. For the most part this system works pretty well and seems to be understood by most drivers.
In New Mexico they looked at this line system and at some point decided it wasn't enough. They added signs. Signs at every change from a solid to dotted line. There are thousands of signs. Not only are there signs to tell you not to pass, but they have signs that tell you that it's okay in addition to the lines.
Pass with care, New Mexico seriously has to tell their drivers to be careful when passing? As opposed to just pulling into the other lane without looking and gunning it? The only logical explanation I can come up with is that some New Mexico State Senator's brother owned a road sign printing business.
Either that or there isn't much logical going on in New Mexico.