The oldest meaning of traffic (trade, commerce, business) has been with us since the 15th century, but it has only signified "people and vehicles coming and going" since the 1820s. Thus the OP would be quite correct to assume a person from the medieval ages would not have used the word "traffic" to suggest a flow of vehicles and people. With the guidance of etymonline, may I suggest the following alternatives:
Old English bisig "careful, anxious," later "continually employed or occupied,"
- The lanes bustled
- The bustle of the city
"be active," 1570s (bustling "noisy or excited activity" is from early 15c.),
Old English crudan "to press, crush."
Dictionary.com dates crowded between 1605-1615
Way is an archaic term for road, derived from Old English weg (ca. 500-1100). In fact, portweg meant "the way to town" or "public road"