The railroad tracks I showed three days ago cut across Webster Groves but aren't much of a barrier (unless you are trying to drive across them when a train comes by, but that's not often). Interstate 44 is another matter. It forms a shallow artificial canyon with far fewer places to cross than the railroad. Much of it is depressed below the surrounding ground level so it's not visually in your face but is something of a scar and a barrier between neighborhoods.
As long as America remains so car dependent I suppose we need it. These roads are much uglier and cause worse social divisions in some other cities.