You get some wonderful ideas, Alfiesgirl, don't you? I'm sure, however, that 'black' in this case is merely a statement of physical fact and not a reference to black as a symbolic colour for death. A road covered in black ice looks no different from a wet road, so you are unaware the ice is there until your car-wheels start doing naughty things! In other words, the ice is said to be black simply because you can't see it, as compared with the more normal 'white' ice which you can.