Moving in Combat

Scarterra d10’s RPG system is not intended to require a grid or battle map, it is played in the mind’s eye. It is often okay to use vague cinematic terms and let characters move “at the speed of plot” and use generic terms “like you are seven successes away from the nearest enemy.” But sometimes you need to assign a concrete number to distance traveled.
A combat round is 30 seconds and you get an A-action and B-Action. If you use either or both actions to run, a human or human-like character rolls Dexterity + Athletics and covers 20 yards per success.
For reference, the maximum range of a long bow or crossbow is about 240 yards so if your characters wants to charge a well positioned archer in order to hit them with a sword, your character needs to accumulate 12 successes.
If a character uses their A-action and their B-action, they can do this in one cinematic round if they roll six successes twice in a row which for context is just a little bit slower than a gold medal class Olympic sprinter. Though that also assumes you aren’t trying to dodge arrows (something that rarely comes up in modern track and field events). If you want your character to run while also defending herself you have to use one action to run and one action to parry or dodge.
The difficulty for running requires a Dexterity + Athletics with a variability difficulty which depend on three primary factors. How much is the character is carrying? How fast the character’s race normally moves? How open and unobstructed is the area the character running through?
A character carrying little more than the clothes his back has a base difficulty 5. A character running with a weapon and shield and light amount of basic adventuring gear (assuming light or medium armor and a backpack with provisions and basic camping gear) is going to have a base difficulty 6. A character carrying a fairly heavy load of gear has a base difficulty of 8 ("fairly heavy" being relative to their own strength score).
Humans are the base-line difficulty and most humanoids run roughly as fast as humans. Tengku, elves, and goblins get -1 on their base difficulty from their innate Dexterity bonus but they have the same base running speed. Satyrs get -1 difficulty from their Athletics bonus which has the same effect in this situation but they also have a higher base running speed.
Gnomes, kobolds, and other characters with the puny trait do not suffer a penalty on their roll, but most puny characters have a movement rate of 15 feet per success rather than 20 feet (goblins are the exception since they evolved to be good at running away). Their legs are shorter and thus their stride is shorter though most smaller humanoids can take additional strides slightly faster which is why they are only 25% slower not 50% slower.
A nice flight featureless plane has no difficulty modifier, but the game master can adjust the based difficulty at his discretion. There are two many possible complications to cover everything that can make running more difficult here, but included are some examples.
-Having a chase scene through a crowded marketplace might raise the difficulty by +1 as you have to run around shoppers and carts full of cabbage.
-Running through an intense battlefield where you have to run around combatants, lose weapons, and the bodies of the wounded and dying would probably constitute a +2 difficulty modifier.
-Steep or uneven terrain can raise the difficulty by +1. Loose or slippery terrain can roll the difficulty by +1 or +2 depending on how severe it is.
If you are running downhill, you move more than 20 yards per success but the difficulty goes up depending on how steep the terrain is. In other words, you are moving faster but you are also more likely to trip and fall down.

What if you don't roll any successes?

It is unlikely that a character won't get any successes on a movement rule but hardly impossible. It doesn't necessarily mean your character didn't move.
A botch means your character had some sort of major accident and probably fell down in an embarassing fashion.
A failure means you might have to stop or swerve to narrowly avoid a major accidents or had to backtrack at some point. In a lot of cases, failed movement rolls meant your character knocked something or someone over.

Free Movement

The rule guidelines above assume your character is making serious effort to move from Point A to Point B. But if you character is not using an action or partial action to move that doesn’t mean your character is not moving at all.
In a real sword fight, it’s not like the combatants are going to stand still and swing swords at each other. They are probably going to be constantly moving, not unlike watching a professional boxing match where the combatants move around the ring. Characters do not have to give up any actions or dice for this assumed movement.
If you are using a battle map or something similar precise, this is assumed to be net zero movement assuming the figuring for every step forward in the fight, your character is going to take a backwards step in the fight, eventually. If your character is trying to move somewhere gradually and defensively, you can move about ten yards for free, unless your opponent is actively to trying to stop you from moving that direction in which case the free movement is negated. If one fighter has the other on the ropes so to speak, that fighter can push the fight two to five yards for free at the Game Master’s discretion depending on how many successful strikes gets in. In this case, soaks and parries are irrelevant, even if a character isn’t taking damage, if one combatant is parrying or soaking more attacks than the other they are probably being forced back at least a bit each time they block an attack or are struck.