The caravan served as the principle method for transporting goods across the Silk Road. This image from "The Silk Road Atlas" depicts what the journey may have looked like.
Source
Eduljee, K.E. "Zoroastrian Heritage." Aryan Trade and Zoroastrianism. Silk Roads. Zoroastrian Heritage, n.d. Web. 07 May 2015. <http://www.heritageinstitute.com/zoroastrianism/aryans/trade.htm>.