Fallout 4 • From Vault 111 to Diamond City without enemy encounter or taking any damage

The video is at 2x speed, otherwise it would be too boring to watch. If you want to see it at normal speed feel free to change the video speed to 0.5 in the video player setting. I use mods, obviously, one of them let me run without losing AP, so if you take the same route it will take you longer, because you simply can't sprint the entire time.
This seem to be the fastest and safest route to reach Diamond City straight from Vault 111 without risking limbs and life. At the end you can also see a little trick on how to skip scripted scenes like the one with Piper. Punch the NPC with your fists and immediately put away your "weapon" or the NPC will pull their weapon and kills you. Enjoy!