The overpass/bus example is an example of bad engineering, not racism. On the other hand, the building of a highway that separated the black neighborhood (or more likely the poor neighborhood that happened to be majority black) from the rest of a city is a real thing, that really was done in places, with the properties condemned by eminent domain to build it, in such circumstances, carved from the black neighborhood, not the adjacent white neighborhood. Yes, back in the days when we built the Interstate Highway system, there really were racists (in the standard English sense, not the Newspeak sense that includes all white people by definition) in places of power making such decisions.