|For a vehicle of the same name in Fallout: New Vegas, see Monorail.|
|The following is based on Fallout: Brotherhood of Steel and has not been confirmed by canon sources.|
The monorail system was designed to provide fast travel between different sections of Vault-Tec's own Secret Vault. By 2208 most cars were destroyed and only a few was still functional. One line also led to a distant location in the mountains, miles away from the Vault, providing evacuation in case of emergency decontamination.