Subway Runner is a unique Fallout 4 mod that connects most of the subway stations around the Commonwealth. 90% of them to be exact.
The mod creates a vast network of subway tunnels that connect various subway stations across the map. Some of these stations have been added to the game.
The tunnels aren't just filled with debris and train wrecks. As you explore, you'll encounter various Ghouls, Raiders, Super Mutants, and Synths. Once you clear out the enemies, you'll be able to move quickly from one place to another, making it an ideal mod for those playing the game on Survival Mode.
You'll be able to move around unseen and you'll also find beds. Survival Mode requires you to find a bed in order to save your game.
The tunnels are also companion-friendly which means you can take Dogmeat, Nick Valentine, or whoever you want with you.