Hmm. One star or five stars? One star for being absolutely dangerous. It is such a ridiculous grade that, yes maybe it should be illegal. How would you even access it at all in the winter? There are people living on this street but it would be completely impossible to drive up or down with snow on it. Actually believe it or not, it's even too steep to drive on it when it's wet. Driving down it Is actually illegal, but do it anyways to get the full experience.
I shall give it five stars. For being the steepest street in the world. For its vast amount of character. Character above practicality in this case. It's an old cobblestone street that is not very kept up. You could argue that that is a bad thing. Nah, I say. More character. Where but Pittsburgh would you find a street like this?