I've made the same observation as Capt Bloggs on more than one occasion. The ability to put .1NM right in (or have it automatically fed in) above 20,000' would be enough to stop the head on case - the GPSs are that accurate. (I know it doesn't fix the crossing problem, but if you knew someone was going to fire a bullet over your head on a fixed line, would you be happy to stay on that line and rely on his aim to fire it over your head, or, being a 'belts and graces' man (as most would hope all airline pilots are), would you take one step to the side as well, 'just in case'?