HOW 1.5 INCREASES WORK: 1st point is only one. Second is two, third is one, fourth is two, etc.

Fatigue costs are cumulative: if you're walking for 5 turns and rest for a bit, you'll get the 1 point cost when you get up. This is for all of them, not just movement. Body armour fatigue costs do it too.

Things that cause fatigue: running, crawling, walking over long distances, movement over rough terrain, jumping, fighting, being shot, being clubbed, being punched, falling, lifting heavy objects, trotting about in body armour, etc.

Things that recover fatigue: rest, sleep, relaxation, break-taking.

If a character has trouble breathing, whether from a gas mask, lung injury, etc., exertion has a higher fatigue cost.
Minor: "every X turns" reduced by 1, to a minimum of 1.
Moderate: "every X turns" reduced by 2, to a minimum of 1.
Significant: "every X turns" reduced by 4, to a minimum of 1.

If winded: no running, sprinting, jumping or climbing.

Fatigue costs:
+:

Walking: 1 point every 4 turns if unfit, every 6 if fit.

Running: 1 point every 2 turns if unfit, every 4 if fit.

Sprinting: 1 point every turn if unfit, every 2 if fit.

Crawling: 1 point every 2 turns if unfit, every 3 if fit.

Climbing (steep slope, tree, wreckage, ladder etc.): as crawling.

Climbing (rope, building, cliff, pole etc.): 1 point every turn.

Jumping: 3 points of fatigue if jumping up or leaping, 1 if jumping down. Fitness does not affect fatigue costs, only distance.

-:

Resting: +1 point of fatigue regained per turn. +1.5 if reasonably comfortable. This is in addition to the normal recovery rate.

Sleeping: +1 points of fatigue per hour. +2 if in a proper bed, warm, etc. This is in addition to the normal recovery rate.

Being alive: 1 point recovered every 12 turns if unfit, every 9 if fit. This also applies when resting.

Modifiers:

Rough terrain (rocky ground, forest, minor rubble etc.): reduce "X turns" by 1, to a minimum of 1.

Broken terrain (boulders, lots of fallen trees, building wreckage etc.): reduce "X turns" by 2, to a minimum of 1.

Engaging in hand-to-hand combat: "every X turns" reduced by 1, to a minimum of 1.

If 5 points or more of fatigue are received from a single injury, treat the character as winded for their next turn.

Sleep loss:
There's Fatigue, and there's fatigue. Of them, Fatigue goes away if you sit down for a bit, and fatigue doesn't go unless you sleep/indulge in stimulants. Fatigue is physical, fatigue is mental. They'll both make you less effective, but sleep loss is cumulative. If you exercise too much, you probably won't suffer much the next morning beyond muscle stiffness, assuming you rest well, represented by having a higher Fatigue cost of activity until you've had a chance to ease into things. Mental, though.. if you don't get enough sleep three nights in a row, you'll suffer for it more and more each day. And you'll have a chance of nodding off if you're resting/doing something for more than a few turns. NOT good by any means if you're the driver, believe you me. Someone who hasn't slept at all for two days will be effectively useless in a fight; probably a liability, in fact, since they won't be aiming well and might even mistake you for the enemy if things more too quickly for them to keep track of.

One day of sleep deprivation (or two of insufficient sleep):
For every action carried on outside of combat for more than 3 turns: roll 1-10. If 3 or less, character nods off for 1-5 turns.
If character wakes up: -1 "per turn number" on all activity related fatigue costs for 1-3 turns. Walking would be 1 point every 5 turns, etc. This also applies to waking up after a nap.