TEXT: Overland Journeys
  Variant rules for extended travel in 5th Edition Dungeons & Dragons
  
  Overland Journeys
  W
  ithin the standard 5th Edition ruleset, there's
  very little space given over to the 'third pillar'
  of the game experience - exploration. Many
  DMs will either gloss over extended travel
  with nothing more than evocative narration, or
  simply craft their campaigns to avoid having to
  deal with it in the first place.
  These rules are intended to provide a way for DMs to
  include epic quests and gruelling journeys, where simply
  getting from A to B is a feat in itself.
  Journeys as Dungeons
  The classic dungeon crawl is as old as D&D itself, and many
  an adventure is built entirely around a party's daring delve
  into a dark demense, in search of fame, fortune and sweet,
  sweet experience points. This ruleset effectively re-imagines
  an overland journey as a kind of dungeon crawl, with each
  room in the dungeon being replaced by a scene on the
  journey.
  Long Rests
  The biggest issue with overland travel, from a DM's
  standpoint, is that the party will be able to get a long rest
  every night. This means that unless the DM chooses to pack
  the journey full of four or more encounters every day, the
  party will be full rested and refreshed for almost every
  encounter. To correct for this, introduce the following
  modification:
  Variant Rule: Resting on the
  Road
  For the player characters to take a long rest, they
  must ensure they have at least a basic level of
  comfort and safety. Comfort requires each
  character to sleep in a bed, with four solid walls
  and a roof above them. Safety requires the party to
  not need to set a watch overnight. Unless both of
  these conditions are met, the rest only gives the
  benefits of a short rest.
  Step 1: The Route
  Upon beginning a journey, first determine the route to be
  traveled, noting the distance and the terrain type. Each type
  of terrain has a travel speed and a travel DC, as noted below.
  Terrain Types
  Terrain should be classified into one of the types below,
  which are shown with their corresponding maximum speed
  and travel DC:
  Good Roads. Max speed: Fast. Travel DC: 5. Safe, well-
  traveled roads and trade routes, often connecting major
  cities. Navigation is trivial, and danger is rare.
  Bad Roads. Max speed: Fast. Travel DC: 10. Old roads,
  disused or bandit-prone, connecting towns or running
  through dangerous wilderness areas. Navigation is simple,
  though the road sometimes vanishes for stretches of a few
  miles, and dangers are more common.
  Grassland. Max speed: Medium. Travel DC: 10. Rolling
  hills, plains, or farmland, potentially with game trails or other
  pathways. Navigation is by landmark and the horizon, and
  there are often predators and other dangers to be mindful of.
  Forest. Max speed: Slow. Travel DC: 15. Thick woodlands,
  forests and other areas of heavy tree cover. Navigation can be
  hard, without paths or trails, and dangers lurk beneath the
  boughs.
  Swamp. Max speed: Slow. Travel DC: 20. Bogs, marshes
  and swampland, with uncertain footing and inhospitable
  quagmires. Navigation is tough, and dangers abound.
  Mountain. Max speed: Slow. Travel DC: 20. Cliffs,
  mountain passes, clustered caverns and ragged ravines.
  Trails are few and far between, passes are narrow and hard
  to cross, and predators prowl the peaks.
  Desert. Max speed: Slow. Travel DC: 25. Dessicated dunes,
  shifting sands and barren wastes, with little in the way of
  sustenance or guiding landmarks. Footing is uncertain, days
  are sweltering, nights are chill, and predators stalk any
  travellers.
  Arctic. Max speed: Medium. Travel DC: 20. Freezing
  glaciers and snow-covered reaches, far from the grasp of
  civilisation. Navigation is hard in the snow, and dangers can
  creep close without warning.
  Underdark. Max speed: Medium. Travel DC: 25. A web of
  subterranean tunnels and subsurface mushroom forests,
  infested with monsters and precarious empires of drow and
  duergar. It's easy to be turned around in the Underdark, and
  even easier to fall victim to one of the many threats.
  Travel Speeds
  Each terrain type has its own travel speed, which is the
  amount of miles the party can cross each day of travel.
  Slow. 10 miles per day
  Medium. 20 miles per day.
  Fast. 30 miles per day.
  1
  PART 1 | THE ROUTE
  
  Example
  Alberic, Bern, Charise and Darius are travelling from
  the town of Secomber deep into the High Forest in
  search of a lost temple. It's a long, arduous trek
  through the huge woodland region, and the group
  estimate the whole journey to be roughly two
  hundred miles.
  Forest terrain has a travel speed of Medium,
  which equates to twenty miles per day. This means
  that the trip should take around ten days of travel.
   
  Step 2: Embarking
  With the journey duration and difficulty assigned, it can be
  populated with events. The number and difficulty of
  encounters the party finds along their quest will be modified
  according to the party's skill in the roles below, to result in a
  dynamic, reactive journey.
  Remember that not all encounters have to be combat, or
  even hostile. Think of each encounter as a "point of interest"
  along the route - an opportunity for the DM to zoom in on the
  party as they find something interesting, or a potential threat
  to avoid or confront.
  Roles
  Once the party has planned their journey, the There are four
  roles for the party to fill along the journey, the Navigator, the
  Lookout, the Scout, and the Hunter. Each role requires a
  skill check, the results of which will affect the time it takes
  the party to complete the journey and the difficulties they face
  along the way.
  In parties with fewer than four members, each character
  can fill up to two roles, though if they choose to fill two roles
  their skill checks for both will be made with disadvantage.
  In parties with more than four members, up to two
  characters can fill each role - in a role filled by two
  characters, the character with the highest modifier for the
  check makes the skill check with advantage.
  The Navigator
  The Navigator is in charge of reading the map, orienteering
  and keeping the party on-course and on-time. At the outset of
  each journey leg, the Navigator makes an Intelligence
  (Survival) check against the terrain's travel DC, with the
  result affecting how quickly the party can complete the
  journey.
  Pass by 5 or more: Short-cut. The journey's travel time
  is reduced by 10%, and if there are any long rest locations
  along the way, the party will find them.
  Pass: On-track. The journey takes the expected amount
  of time.
  Fail: Off-course. The journey's travel time is increased by
  50%.
  Fail by 5 or more: Lost. The journey takes twice as long
  as expected.
  The Lookout
  The Lookout is in charge of watching for danger, alerting
  the party when bandits or roving predators are near, and
  keeping an eye out for places or things of interest along the
  way. At the outset of each journey leg, the Lookout makes a
  Wisdom (Perception) check against the terrain's travel DC,
  with the result affecting how many encounters the party will
  come across along the journey.
  Pass by 5 or more: In the clear. The party will see 1
  encounter per ten days of travel.
  Pass: Interesting times. The party will see 2 encounters
  per ten days of travel.
  Fail: Dangerous terrain. The party will see 3 encounters
  per ten days of travel.
  Fail by 5 or more: Stalked by misfortune. The party will
  see 4 encounters per ten days of travel.
  The Scout
  The Scout is in charge of assessing the terrain ahead, and
  steering the party clear of monster lairs and environmental
  hazards. At the outset of each journey leg, the Scout makes a
  Wisdom (Nature) check against the terrain's travel DC, with
  the result affecting the difficulty of the encounters the party
  will face along the way.
  Encounter difficulty is adjusted by the DM using the CR
  system on page 274 of the Dungeon Master's Guide.
  Pass by 5 or more: No threat. The journey's encounters
  will be Easy.
  Pass: On guard. The journey's encounters will be
  Medium.
  Fail: Uncertain territory. The journey's encounters will
  be Hard.
  Fail by 5 or more: Danger abounds. The journey's
  encounters will be Deadly.
  The Hunter
  The Hunter is in charge of keeping the party fed and watered,
  tracking down game animals, searching for fresh water, and
  monitoring the party's supplies. At the outset of each journey
  leg, the Hunter makes an attack roll against the terrain's
  travel DC, with the result affecting how physically draining
  the trip is.
  Pass by 5 or more: Abundance. The party consume no
  supplies, as food is plentiful. Each player characters may
  remove one level of Exhaustion, if they have any.
  Pass: Good hunting. The party consume their supplies at
  half the usual rate, if they have any, as they can forage
  sufficient food to sustain them.
  Fail: Sparse pickings. Game is in short supply - the party
  can only find enough forage to just about keep them alive,
  and must rely solely on their supplies for solid meals and
  clean water. If they run out, each member gains one level
  of Exhaustion for each ten days travelled without supplies.
  Fail by 5 or more: Barren. Game is absent and the party
  is unable to find sources of potable water - the party
  consume their supplies at double the usual rate, if they
  have any. Should they run out, each member gains one
  level of Exhaustion for each ten days travelled without
  supplies.
  2
  PART 2 | EMBARKING
  
  Example
  Alberic, Bern, Charise and Darius are about to set
  off on their trek through the High Forest, and each
  of them chooses a role. The forest's travel DC is
  15, so they'll each make their checks against a DC
  of 15.
  Alberic, a learned wizard, chooses to navigate.
  He makes an Intelligence (Survival) check and
  scores a 16 - a pass. The party will be on-time to
  make the journey in the expected ten days.
  Charise, a cunning rogue, chooses to be the
  lookout. She makes a Wisdom (Perception) check
  and scores a 19 - a pass. The party will see two
  encounters across their ten-day trip.
  Bern, as a wise druid, elects to scout. He makes a
  Wisdom (Nature) check, but only scores a 9 - a fail
  by 5 or more! The two encounters the party faces, if
  they turn to combat, will be Deadly!
  Darius, a skilled fighter, takes charge of hunting.
  He makes an attack roll, and scores a 14 - a failure.
  Luckily, the group brought enough rations and
  supplies to last them the full ten days, because
  they're forced to rely entirely on rations as forage and
  food is little to be found. If anything happens to
  them, the whole group would be forced to gain a
  level of exhaustion!
   
  Step 3: The Encounters
  With the journey's real duration determined, and the number
  and difficulty of encounters along the way decided, all that
  remains is for the Dungeon Master to combine it all into a
  cohesive whole.
  Premade Encounters
  Should the DM wish, each encounter along the route can be
  pre-planned in advance. The DM might decide that the party
  will first wander into the territories of an isolationist enclave
  of wood elves, before a few days later stumbling across the
  entrance to an overgrown temple still crawling with foul
  undead, for example.
  This approach works best if there is either sufficient time
  between the outset of the journey and the actual in-game
  traveling for the DM to plan out these encounters, or if the
  DM already has enough workdbuilding detail in place for the
  region - it allows the encounters the party face to both evoke
  the foes and themes of the campaign, but also to be carefully
  crafted for the party themselves.
  Random Encounters
  If the DM prefers, they can simply roll on the random tables
  found on pages 92 - 112 of Xanathar's Guide to Everything,
  which are broken down by terrain type and Challenge Rating.
  As a simple conversion:
  For Easy encounters, roll on the table for the level bracket
  below the players.
  For Hard encounters, roll on the table for the level
  bracket above the players.
  For Deadly encounters, roll on the table for the level
  bracket two above the players.
   
  Example
  The DM for Alberic, Bern, Charise and Darius elects
  to roll for the two encounters the party will face
  along their journey. The party are level 7, but
  thanks to Bern's fumbling scouting their
  encounters will be Deadly, so the DM finds the
  table for Forest encounters at levels 17+ (XGE
  p.100) and makes two rolls.
  She gets an 18 and a 91 - a herd of unicorns,
  and an ancient green dragon. She's confident that
  the good-aligned party won't find conflict with the
  unicorns, but the ancient dragon is far above their
  weight class: the four adventurers will have to play
  their cards right to avoid a potentially lethal fight.
  Notes
  There are some class features or other game elements that
  can alter how the DM might like to use these rules, which are
  addressed below.
  Characters with the Outlander background. The
  Wanderer feature states "you can find food and fresh water
  for yourself and up to five other people each day, provided
  that the land offers berries, small game, water, and so forth."
  As such, it is recommended that if the character with this
  feature takes the Hunter role, they make their attack roll with
  advantage - their background helps them find what game is
  around, but cannot help if there simply is nothing to find, after
  all.
  Rangers with Favoured Terrain. The Natural Explorer
  feature grants a number of benefits which sadly see little use
  in many campaigns. With this in mind, it is recommended
  that they apply to these journey rules as such:
  If the journey is made through the Ranger's favoured
  terrain, the party's maximum speed is raised by one level
  (from Slow to Medium, or from Medium to Fast).
  If the journey is made through the Ranger's favoured
  terrain, the terrain's travel DC is lowered by 5.
  If the journey is made through the Ranger's favoured
  terrain, the Ranger makes their check for any role they fill
  with advantage.
  3
  PART 3 | PUTTING IT ALL TOGETHER
  
SOURCE: textdata/thevault/Dungeons & Dragons [multi]/5th Edition (5e)/3rd Party/Homebrew/Overland Journeys.pdf