I'll have a bit more data soon on the vanishing + lengthening commutes of South Dallas residents (and how those two issues are tethered), but first, a graphic on the average commute times:
Highways form two types of barriers in cities: physical and distance. The former is immediate and obvious, but in all likelihood not as subtly pernicious as the latter. Jobs continue to spill northwards year after year. As jobs get further and further away, what's the point in staying? Those with means end up leaving for more opportunistic places elsewhere. The area is left to die on the vine. Yes, 30 is a problem but it is more symbolic. 345 is what siphons the life out of South Dallas.
Turning and turning in the widening gyre
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold;
Mere anarchy is loosed upon the world,