Thanks to the post on The Hydra's Grotto, I decided to use 6 mile hexes instead of the usual 5 mile hexes. This fits perfectly with D&D 5e. According to 5th edition rules; a party travels 24 miles a day, 18 miles if cautious and 30 if travelling at haste; which translates to 4, 3 or 5 hexes per day. How do Wandering Encounter rolls work 5e rules are a bit vague on the how' and whys of random encounters. But basically, when a GM thinks that there might be a chance of a random encounter, they roll a d20; on a 18-20 a random encounter occurs. The details are left to the GM.
Wandering Encounterdescriptor, Every hex in the overland map has a one of these. This will either be 'NO', x1, x2 or x3.
No: Means that there are no random encounters in that area.
x1: Is the standard Wandering Encounter; roll a d20 and 18-20 triggers a random encounter.
x2: Is for regions that are more densely populated with potential encounters; roll 2d20 and any die that comes up 18-20 triggers a random encounter. A 2nd 18-20 means making 2 random rolls and using both the results.
x3: This is for very heavily populated areas, such as enemy bases or encampments. Roll 3d20, a single 18-20 triggers a random encounter, further 18-20 results trigger additional random encounters.
Wandering Encounter Roll A wandering encounter roll is made to determine if a random encounter will occr or not Below are the conditions that generally trigger a wandering encounter roll.
Every time the party enter a hex.
Every short and long rest.
Generally, any skill use that is related to overland travel - IE a tracking roll, or survival roll.
Generally an activity that take at least 30 mins to perform
The Random Encounter Roll The random encounter roll determines what the kind of encounter it will be.
In my overland map, every hex is divided into 2 types of area, standard areas and named areas.
Standard areas are hills, forest, grassland, swamp etc. Each standard area has it's own random encounter table, this will vary according to the general difficulty of that region. So starting forests will be populated with less dangerous encounters, later forests will have more potent random encounter tables.
Named areas will have their own tailored random encounter tables.
Encounter Type Roll Finally; a roll will be made to see what kind of encounter it will be. In a west marches game, pretty much everything encountered will be a threat of some sort or other. Roll a d6:
1: PCs have the advantage at the start of the encounter.
2-5: Neither side has advantage.
6: The other side has the advantage, this could be surprise, ambush or whatever the GM sees fit to use.