Yes, I've seen this happen before. Why? The carz are stopped for the train... BUT, the short section of road continues to spawn carz. So they just pile up inside each other. You have to just learn to lay your roads carefully so this doesn't happen. Don't put a short section of track like this right near a crossing. And don't put a spline circle too close to a crossing either or the carz will continue across the crossing, even if the crossing bars are down, right thru the train.