Fallout, Fallout 2 and Fallout TacticsEdit
When stepping on the exit grid in any map, one will enter the world map. If one wants to get anywhere at all, fast traveling is required.
Moving across the vast desert takes a varied amount of time based on the terrain; mountains cause slower travel, while deserts are easier to get through.
Driving in a vehicle such as a Chryslus Motors Highwayman in Fallout 2 or a Brotherhood Hummer in Fallout Tactics in will increase one's fast travel speed, but only as long as there's gas in the tank.
Fast travel in Fallout 3 is significantly more simple. Simply select any discovered location marker from the world map, and one can fast travel to it. Any fast travel, be it from Raven Rock to Rivet City, or from Vault 101 to Megaton, will take one game hour to complete.
One cannot fast travel to locations that haven't been formally discovered, and cannot fast travel while inside a location, while in the air (such as in the middle of a fall), while overencumbered or while in the vicinity of or fighting enemies.
Fallout: New VegasEdit
Fast travel in Fallout: New Vegas is identical to that of Fallout 3 except in the time it takes to get to one's destination. The player character may also fast travel while overencumbered using the Long Haul perk. If one travels to a close destination, time seems to pass in increments of 10 minutes, while farther destinations result in increments of hours. Holding a two handed weapon does not affect the time it takes to travel, but sneaking while fast traveling will increase the time it takes. One can only fast travel to locations already discovered and visited prior.
Fallout 4 Edit
Fast travel in Fallout 4 is identical to fast travel in Fallout 3, except that the game time increment during fast travel is dependent on the distance traveled, unless traveling to and from the Institute. Fast travel from opposite corners of the map takes about 2 hours and 15 minutes game time at the default timescale of 20. Decreasing the timescale causes the fast travel to take much more game time (about 7 hours at timescale 10).
The Sole Survivor can mitigate the traveling time by using the Institute as a jumping platform as it only takes one in-game minute to teleport to and from it.
There are four locations that allow fast travel to and from an inside location: the Railroad HQ, Home Plate, the Institute and The Mechanist's lair.