During the time this verse was revealed, mankind had no idea that in the future things other than animals could be used for transportation. That is why Allah states in this verse: He has created (other) things of which you have no knowledge. In fact, the history shows that mankind has continuously discovered new methods of transportation. At any given point of time, a few means of transportation were always unknown. This verse thus is true for all generations of mankind. (The Quran, 16:8)

Surat An-Nahl (The Bee) 16:8

He created the horses, mules and donkeys for you to ride and [as] adornment. And He creates that which you do not know.