You're Using Mounts All Wrong!

 Or: "Horses Aren't Bicycles."

Consider the following scenario: the party wants to go somewhere that is Far Away. They ask the GM how long the trip will take, which results in some quick math dividing the total distance by the daily movement speed of the party. The players, hearing the result, wince and ask how much four horses would cost. They pay the fee and reduce their travel times by half. The horses are never brought up again outside of reminding the GM that the party now travels at horse speed, not walking speed.

Or, alternatively, one of the players buys a lance to go with their horse and leans into trying to joust anyone hostile-looking who they encounter in an outdoor setting. This is represented by the fact that the mounted character now moves at 60' per round, rather than 30', but still has the exact same maneuverability as a character moving around on foot.

Those are both obvious nonsense, but they share the same source: tables treating mounts as equipment, when they should be treated as hirelings. And not just nameless hirelings: the sort of hirelings who change over time, gaining personality and character as they go through shit right alongside the PCs. The sort of hirelings where you remember their names.

To that end, I propose the following two rules:

1. Use Horse Gaits.

Different horses move differently. Each horse is capable of a handful of 'gaits' (ways of moving) but a trot from a work horse and a trot from a race horse are two very different trots. Giving each horse unique gaits goes a long way toward making horses feel like specific individuals.

Walk. Every healthy horse can walk at a pace of 40' per round or 30 miles per day at a sustainable pace. If you're not doing some sort of 'changing horses at every stable' Pony Express business, this is as fast as horseback travel normally goes. Gait options don't change this any: if you canter four miles at the start of the day, your horse gets tired an hour sooner and you end up making the same net distance that day.

Trot vs. Pace. Every healthy horse can either trot or pace. Both are faster than a walk but can only be maintained for a limited amount of time. An average trotter moves at 80' per round for up to an hour at a time and an average pacer moves at 60' per round for up to two hours. Once a horse is tired from trotting/pacing, they need an hour of walking rest before they're ready to go again. Pacing is easier on untrained riders and gives a +4 bonus to any check required to stay in the saddle.

Race horses have a faster trot than usual (with 100' per round for 30 minutes or 150' per round for 20 minutes being common race horse trots) while gaited horses (ie. ones who can pace) can be trained to amble for longer and longer durations (3, 4 or even 5 hours) at their pace speed. As with pacing, ambling is easier on the rider and lets you do things in the saddle that would be much more difficult atop a trotting horse.

Canter vs Gallop. Every healthy horse can do one or the other. Some can be taught to do both. Horses who canter so at 100' to 200' / round for up to 4 miles, while horses who gallop do so at 250' to 300' / round for up to 2 miles. Once a horse is done cantering or galloping, they must walk or trot for an hour before they can do so again. Pacing and ambling doesn't count, which is one of the main reasons to prefer a trotter.

Weird Gaits. If you have a weird horse (or horse-like critter) it can have a weird gait. Kelpies can swim, fairy horses can canter onto a fairy trod, nightmares disappear into hell when galloping and skeletal steeds sacrifice their ability to trot for endless stamina at a walk.

2. Use Horse Morale.

Horses are naturally very skittish creatures. They are often afraid of things that are unfamiliar to them and need coaxed into understanding that an umbrella is not going to hurt them. Or cows. Or butterflies. Or lines painted on the ground. Or smaller horses. Every horse has their own idiosyncratic and characterful list of things that spook them. When buying a horse, working out its personality is just as important as working out what breed it is and how fast it can gallop. Hence, Horse Morale.

If you're using a system where Morale is 1d20, roll under, a horse starts with 6 Morale, +2 per thing this particular horse is spooked by. If you're using 2d6 Morale, a horse starts with 5 Morale, +1 per thing that spooks it. Horses bought at a stable start out spooked by 1d4-1 random things and thus have between 6 and 14 Morale (d20 Morale) or between 5 and 8 (2d6 Morale). Brave horses are weirder and weird horses are braver.

When horses encounter something scary (combat, loud noises, being injured, monsters) or sufficiently strange (to a horse), they test Morale. If the source of the fear is something this particular horse is spooked by, the rider needs to spend ten minutes coaxing their horse before the Morale test can even be attempted. Successfully coaxing a horse to overcome its fear on three occasions means it loses its fear. If the whole party has horses, roll a single die for all the horses, such that skittish horses either all spook at once or not.

On a success, the horse is unbothered. On a failure, the owner of the horse picks out a new idiosyncratic feature of the situation for their horse to be spooked by going forward and adds +2 Morale to their horse. If there's a goblin with a blue scarf threatening the PCs with a magic wand, the horse is more likely to be afraid of blue scarves or people holding sticks than it is to be afraid of goblins. Horses are weird like that.