Central Station is a lore friendly alternative fast travel for survival mode.
Across the commonwealth there are 6 stations you can unlock in order to gain access to the subway network. There are only a couple stations so you will still be walking a fair bit!
Stations are located at Red Rocket, Diamond City, Natick, Boston Airport, Quincy and Salem.

Install Instructions:
Download using NMM (Easy)
When installing manually (Also Easy!), ensure your INI is configured to allow archive invalidation, then extract the Data folder of the mod to your own data folder, overwriting if prompted.