Zzarchov has a great house rule for handling the rigors of wilderness travel:
"I use more abstracted rules than this, basically boiling down to you take damage as you travel and heal slowly while going through the wilderness without creature comforts ... as well as different terrain types having different "Miles per day" ratings. This leads to two things: 1) an increase in taking the longer route if it passed through civilization, roads and inns; 2) No more 'rushing through the wilderness', the bean counters came out and 'frontier living' was replaced with carefully planned expeditions."Let's shamelessly steal the idea. It feels like the perfect abstraction that highlights the contrast between traveling through civilization and wilderness without bogging down into a level of detail that would detract from the evening's fun.
Essentially, every hex of wilderness (at the macro scale, roughly speaking 1 hex = 1 league = 1 day's travel on foot) will deal X hp of damage per day as it is traversed. Roads, settlements, proper provisions, the right clothing, and such will all reduce the damage taken. This damage is applied to everyone traveling, including animals. The damage abstracts all negative aspects of travel, such as animals foundering and an increased chance of disease.
Tally the following adjustments to find the total damage taken per hex traveled. Select one value from each column of the following table:
Terrain type is highly abstracted and can be expanded to fit more thorough hex maps. Climate uses the five main definitions of climate according to the Köppen-Geiger climate classification. Season is a temporal factor, so after every hex has been populated by terrain and climate type, the DM will have to throw in season as well. Likewise with roads; roads could also be defined as major roads (such as Imperial highways or Reichsstraße), maintained roads between towns, and trails that are only maintained by foot traffic. However, the road modifier would not apply to the entire hex, rather only if the party was traveling along it.
The following situational modifiers are applied on the fly and are not part of a hex's intrinsic HP penalty.
This provides a backbone for an abstraction to cover overland travel. An enterprising DM can calculate the HP loss value for each hex on their map and have a valuable resource for gameplay. More situational modifiers can make the calculations more robust if needed. Feel free to chime in with any suggestions on adding more entries to either table.