Velocity of the Undead It's pretty simple to consider velocity. You see a zombie rumbling towards you at 3 m/s. You better run faster than 3 m/s to survive. Simple as that. You have a zombie approaching you from a perpendicular hallway, approximately 20 meters from the entrance, moving up to 4 m/s (You can't see the zombie, so you better be preparing for the worst here) If that zombie covers 4 meters in one second, it will cover that 20 meters in 5 seconds. That means you have less than that 5 seconds to run past that hallway before the zombie can block the exit. You happen to be about 30 meters from that entrance when that zombie starts to approach you. To cover 30 meters in 5 seconds, you must be going 6 meters a second to make it out of there alive. To be reasonable, though, keep in mind that you are a living human, and you tire after a while. Zombies do not tire, so they don't slow down. If you slow down to a velocity slower than the zombie behind you, then the zombie will catch up over time.