COMBAT TURNS & INITIATIVE PASSES
As an update to RAW [SR4A, 144], each turn remains 3 seconds long but passes are updates as follows:
1) There are 3 movement passes per combat turn, each lasting one second. Characters earn movement on their initiative score (as referenced below) losing it if not used in the pass.
2) On movement passes 1-3, characters earn their action passes as appropriate. Characters with only one action only earn an action on the first movement pass, etc. Characters with 4 passes, earn that pass on the end of the third movement pass. Characters with 5 passes earn that at the end of the second movement pass.
* Characters with 3+ movement passes lose any held passes when a new one is earned.
* Characters with 3 or less passes may act in any pass after they have earned a pass. They may not act more than once in any given pass. ergo: If a character with 2 passes holds action until movement pass three, he only gets one action in the turn.

MOVEMENT
As an update to RAW [SR4A, 149], to support movement passes and align movement closer to real life, movement is updated as follows:

Race	Rate per Pass
	Walking	Running	Sprinting	Sprint hits	Per additional pass
Humans, Elves, Orks	1.5m	3m	6m	+1.0m/hit*	+0.5m/add pass
Dwarfs	1.0m	2m	4m	+0.5m/hit*	+0.5m/add pass
Trolls	2.5m	5m	9m	+1.5m/hit*	+0.5m/add pass

Walking
Walking is defined as leasurely moving by walking. Walking incures no penalties to actions.
Running
Running is effectively jogging. It incurs the standard penalty of -2dp to ranged combat. Other penalties will be assessed by GM judgement call.
Sprinting
Sprinting is all out. Effective ranged combat is not capable when sprinting. Characters can use the running skill to increase movement. Hits are capped at running skill +1. ergo. characters who are defaulting can still get a success.
Reminder [SR4A, 136]: The gamemaster may apply modifiers for various types of terrain (slippery, rocky, and so on) and other conditions.
Effects of Additional Passes
Reaction enhancers that increase the number of physical passes that a character receives simply affects their ablity to pump their legs faster. This translates into faster movement as well for each pass after the first. This bonus applies to walking, running & sprinting.

FATIGUE
A character can sprint for a number of turns equal to his Body plus the hits on a Running (Long Distance) + Strength Test before he or she begins to lose steam. If the character continues to run beyond this base period, he or she begins taking 1 box of Stun damage each Combat Turn from fatigue; this damage cannot be resisted. If a character is merely jogging along at his base running rate instead of sprinting, the gamemaster should increase the base period to (Body + hits) x 2 minutes, and only apply 1 box of fatigue Stun damage each time that period passes (rather than each Combat Turn) The maximum amount of fatigue that can be taken is 6 boxes of Stun. After that point, the character must make a Body + Willpower (2) Test each Combat Turn (sprinting) or Body + hits minutes (jogging). If the character fails, he collapses from exhaustion and is simply unable to continue any sort of strenuous activity until he rests. [SR4A, 164]