Not sure if it's the topic you abandoned, but runway incursions certainly seemed hot for a while. Someone else posted here a few months back, trolling for ideas to prevent incursions via some form of visual alert. I think I suggested powerful red lasers for painting giant vibrating X's on the taxiway pavement for no-go zones, and for progressive taxi, big arrows dynamically painted in front of planes with the N-# or flight number tagged on it.

Never heard back