The origins of elevating highways was racism. Dividing the "prosperous" white neighborhoods from the Hispanic/Asian/black neighborhoods (in some cases the groups from central and southern Europe apply here too). Now it's not always the case. The FDR south of the Brooklyn Bridge, in Manhattan has an elevated highway. So it's mixed
To start this out, I don't think that highways care if you are white, black, or hispanic. Secondly, they are built for convenience mostly. Do you suggest getting rid of bridges because they are "Elevated racist highways?" Oh, what about overpasses? Let's get rid of those racist things too! Oh, and let's lose real estate, because we would have to make room for highways on the ground, instead of just their support columns. What is up with people these days? Highways, elevated or not are not people, and are inanimate, therefore making it impossible for them to be racist.
While Adam2 may very well be rights, and I can't say that the history of vehicular structures are my strongest point, elevated highways are neither racist, or inherently cause racism. Simply because something can be used in a bad way does not render that object immoral or wrong. As it is, these raised roadways allow for efficiency and help to reduce traffic, especially in big cities.
It's got very little to do with racism or separating classes and races. For example, the now-dismantled West Side Elevated Highway in New York was made to divert traffic from Eleventh Ave, which became known as "Death Avenue" because trains and car accidents were commonplace.
It was so congested and dangerous that emergency services literally couldn't get through, so they were forced to create an elevated highway.
They don't create these roads to be racist. That's preposterous. They are made to streamline traffic and de-congest busy roads. For example, The Autobahn in Germany was made to increase trade and transit and create work for a wartime Germany. The closest roads got to racist was in 1908, when the first real highway opened, the Long Island Motor Parkway, which required a toll, because it was mainly used for races and the like, until the 30s where it was shut down.