Dammit, you aren't supposed to notice how various urban interstate viaducts channel and wall off some undesirable neighborhoods.
Example: The St Pete, FL system quartered the peninsula, and walled off the black area of town, with only four easily barricaded exits, and a wide open kill zone across the top.
In fact, most by-passes will make it convenient to lay siege and starve out Socialist cities. I-295, around Chicago, is particularly sweet.
Almost like it was planned that way...