Yikes
SAWHORSE
You asked the difference between dead-end vs. common path of egress travel. I'll take a stab at an example:
A dead-end could look (in plan view) like the letter "T", with an exit at the bottom of the r. The upper ends of the T go nowhere: you have to back-up to get out.
A "common path" looks like the letter "P", with an exit at the bottom of the P. You can be at the top of the loop of the P, and exit moving forward in either direction, without having to back up. Unfortunately, no matter which direction you go, you will still end up at the same single door.
The "common path" issue has more to do with separation of exit paths separate, and not rejoining them or getting them too close to each other.
There is a code requirement to keep exit doorways separate (1/2 to 1/3 the diagonal). This is an additional requirement to keep the PATHWAYS to those doors separate as well.
A dead-end could look (in plan view) like the letter "T", with an exit at the bottom of the r. The upper ends of the T go nowhere: you have to back-up to get out.
A "common path" looks like the letter "P", with an exit at the bottom of the P. You can be at the top of the loop of the P, and exit moving forward in either direction, without having to back up. Unfortunately, no matter which direction you go, you will still end up at the same single door.
The "common path" issue has more to do with separation of exit paths separate, and not rejoining them or getting them too close to each other.
There is a code requirement to keep exit doorways separate (1/2 to 1/3 the diagonal). This is an additional requirement to keep the PATHWAYS to those doors separate as well.