Or make mandatory aerodynamic figures, or mandatory hybrid powertrains, or mandatory fuel types... bzzzzzzzzzzzz...
Those sort of solutions are short-sighted and idiotic. Make the law favor more efficient cars. Don't make the law favor a particular implementation. $20 says that someone with a coating patent bought someone with bureaucratic oversight a nice dinner. When the law selects a particular implementation, it runs a significant risk of becoming outdated.
As someone who's other home is Chicago, I can say that sun heating in the winter makes a difference to me (lower latitude, to be fair), and cell phone reception is *already* a problem there.
There is indeed quite a spectrum between dead and alive; Life has never been easy to classify and put into boxes, because the curious thing about it is you never observe the same thing twice looking at it.
And that is why the Abortion debate is so heated. It gets lost in an emotional hissy fit about 'murder' and 'choice.' Nobody seems to bring up the amount of sentience in a fetus at different stages of a pregnancy and where to draw the line between a bunch of cells (not worth protecting in law) and a sentient being (possibly worth protecting in law). As for the US media's constant use of loaded terms such as 'pro life' and 'pro choice,' don't get me started on that.
On a clear disk you can seek forever.