Most Helpful Girl
Faster than it can run.0
Most Helpful Guy
Your eyes can track the zebra as it runs, so it won't.
So suppose there's a fence in front of it, and you can only see through one slot, and thus can't track it.
Standard incandescent light bulbs turn on and off 120 times a second, yet they look steady to most people. Similarly, CRT monitors at 75 Hz look steady to most people. Many people will see them flicker at 60 Hz, however, especially out of the corner of the eye. So, we need to get the stripes to alternate around 75 times a second.
At widest, I'd guess they're about 4 inches wide. 8 inches, 75 times a second is 600 inches / second is 34 mph is 15.25 meters / second is 55 kph.
Take this with a grain of salt. The stripes are not vertical on the ends, they may be wider than 4 inches, different people's visual systems have different tolerances, etc.1