Only use sprint when you want to actually lose a zombie using trees and the like (or if a survivor is trying to kill you, naturally). Zombies have to stop to attack, so as long as you are running they will never hit you. Sprinting uses up water quicker, so save it for when you really need it.|
The hiding in trees works because the zombie melee attack damage uses a line of sight algorithm (the decision to attack is based on alertness and proximity to a target player). I don't know how pine trees are modelled with respect to LOS mechanics, maybe a cone, but it is certainly open to abuse. You can thank the fix that stops zombies attacking through walls for that.
Also, you notice that when zombies start to run they do so in the direction that they were already travelling. That's because their waypointing algorithm gets updated less often than their alertness (wandering/investigating/attacking). The waypointing algorithm checks the alertness state and then sets waypoints depending on which state is active.
Wanderng zombies set a waypoint in open ground up to 100m away and it doesn't get updated as often. Investigating zombies (try eating near a zombie and see what happens) will waypoint to the sound's location. Attacking zombies waypoint to their target's current location. The algorithms don't update the waypoints and states very often. So you have to break line of sight for an appreciable length of time to lose their focus.
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