Fallout, Fallout 2 and Fallout Tactics
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, will increase one's fast travel speed, but only as long as there is gas in the tank.
Fast travel in Fallout 3 involves selecting a discovered location marker from the world map, upon which one can fast travel to. 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 have not 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 Vegas
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 passes 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.
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 14 hours game time at the default timescale of 20. Decreasing the timescale causes the fast travel to take much less 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. Fast travel (including via the Institute) is impossible while the player is overencumbered (and does not have the fourth rank of the Strong Back perk) unless using a Vertibird.
In Survival mode, fast travel is only possible via Vertibird or the Institute. Additionally, while the player can still travel to the Institute from anywhere, the only location to which the player can travel from the Institute is the C.I.T. ruins.
In Fallout 76, the player character can fast travel for free to Vault 76, their C.A.M.P, a party member, the C.A.M.P. of a party member, a friend, Foundation, the Crater, or Fort Atlas. The player character can also fast travel -- at the cost of a small sum of bottle caps -- to other discovered locations, or any camp that has active vending machines. This cost is lowered for player characters under level 25. Fast travel can be initiated from both indoor and outdoor locations, unless there are enemies nearby in which case a 15 second timer is initiated and will automatically fast travel after that time, provided the player character doesn't get damaged. The timer is only triggered by proximity to hostiles, the player's combat status ([DANGER] or [CAUTION]) does not inhibit them from fast travelling instantly.
- Fallout 76 patch 184.108.40.206: "Fast Travel: Cap costs when Fast Traveling have been reduced for players under level 25."