One of the main issues with elevated roadways &#x2F; trains &#x2F; bike lanes &#x2F; what have you over city streets is the relatively dark and undesirable areas they create below them. Seattle had this problem back at the turn of the century, and it generally doesn&#x27;t create a nice urban atmosphere to have massive elevated roadways above the main city, even if it&#x27;s trains or bikes that run on them.<p>That&#x27;s why cities like San Francisco consider tearing down their elevated freeways and replacing them with surface streets -- it creates a more desirable atmosphere when you&#x27;re below. (Think the Embarcadero.)<p>Chicago&#x27;s L is efficient, certainly, but the entire downtown core is hidden under a dark, loud, shaking train track. It&#x27;s not the most pleasant thing to spend your time around.