Murphy's Law in action. With this many flights per day, you need tons of safety measures to ensure that mistakes like this are extremely unlikely. Like "defense in depth", you can't rely on just a few layers of countermeasures, the more the better. So yes, red lights at every intersection are good, but retrofitting planes with a gps-style map that shows exactly where to go and when to turn is even better (and of course probably insanely expensive).