The 6-mile hex has long ago established itself as the default size for overland travel on hex grids for a number of reasons. And I rally quite like it myself. I like consistency.
Hexes are a nice aid for GMs in that you can break down all distances in easy to track chunks, and more importantly can note down where the party of PCs is currently at by simply marking the hex they are in.
One thing that D&D has always gotten annoyingly wrong however, is that the various systems for overland travel speeds all don’t work with 6-mile steps. This whole thing is getting really rambly, but I don’t know how to get it more concise right now, and I really want to get some new stuff on the site.
In B/X, movement speed outdoors is either 24, 18, 12, or 6 miles, depending on a character’s encumbrance. Great. But if you are traveling through forests, deserts, hills, and broken lands, this speed is reduced to 2/3 the normal progress. So 16, 12, 9, or 4 miles. Only one of these is a multiple of 6. Same issue even now in 5th edition. Movement speeds of 30, 24, and 18 miles work great. But not if you cut them to half in any kind of difficult terrain and you get rates of 15, 12, and 9 miles per day.
You don’t actually get the most convenient feature that using a hex grid can provide. You still have to track how many half hexes or even third hexes the party has moved in a given day.
The most convenient for GMs would be a system in which all possible distances are increments of 6 miles. And the only way in which this really works is using base speeds of 36, 24, and 12 miles per day, with all forms of difficult terrain reducing that by half to 18, 12, and 6 miles per day.
|Unencumbered||36 miles||18 miles|
|Encumbered||24 miles||12 miles|
|Heavily Encumbered||12 miles||6 miles|
However, 36 miles is really quite a lot.
But how unrealistic is it really? There are plenty of sources for military references for marching armies that put good progress somewhere in the 24 to 30 miles per day range, though often much less than that. And if you look around for advice on how far people can expect to hike for a day, those 24 to 30 miles numbers show up as well as recommendations for beginners who might be unsure how far they can actually make it in a day. 36 miles in a day is significantly more than that.
But a party of PCs in a wilderness exploration game is usually not an army on the march. Nor are they inexperienced hikers. Also, all those numbers assume 8 hours of moving per day. That leaves 8 hours of resting in camp and 8 more hours of… what exactly? If you’re on vacation and hiking for fun, there’s plenty for you to do during that last third of the day. But moving through dangerous territory to get to an even deadlier dungeon is very much not a vacation. I think adventurers crossing the wilderness would do a bit more walking each day than tourists. And another very important factor is that in most systems, being “unencumbered” usually translates to very light gear with very little weapons, tools, and supplies. When a party is crossing through the wilderness for several days, they won’t be unencumbered. If using the numbers I’ve proposed above, 36 miles in a day would be something that only really happens for messengers in a hurry. No loitering around, carrying only the barest necessities, sticking to roads and easy ground. And in that context, 36 miles in a day does not seem that implausible. Much more common, at least for the campaigns that I run, would be traveling with a medium load, mostly going through forests and swamps, which would reduce the usual distance per day down to 12 miles. A much smaller number.
And at the end of the day, we’re talking about a game that has hit points as one of its basic mechanics. We’re not running an actual simulation of anything here. Also, any amount of miles really is just a made up number in an almost undefined virtual space, not any actual physical distances. Might some people think that 36 miles in a day is a bit of a stretch? Sure, why not. And I am not going to argue with anyone on whether that can actually be sustained for more than a day or two. But having to bother with only full hexes and not dealing with any fractions or partial hexes is a big convenience for running fantastical adventures in a made up space, and that’s the part that really matters.