I only saw this once, but it was an interesting one. The high LOD zone did not load when I was in the city, even though I walked right up to the zone. So I was left with the low LOD zone. Here are some pictures: Cars were blocked by the low LOD zone and so were piling up when they hit it. Johnny Gat also got stuck here.
Someone else reported a similar issue on the Steam forum here: http://steamcommunity.com/app/304530/discussions/0/1473096694448640882/
