Final answer:
Trade on the Royal Road peaked during the Pax Mongolica era of the Mongol Empire from 1207 to 1360 CE, when the Silk Road network was highly active and facilitated extensive cultural and economic exchange.
Step-by-step explanation:
Trade on the Royal Road reached its peak during the Pax Mongolica era, under the expansive Mongol Empire, which lasted from 1207 to 1360 CE. This period marked the zenith of Silk Road activity due to the political stability and uniform administrative policies across the vast territories under Mongol rule.
These factors facilitated trade and communication, leading to increased economic integration and cultural exchange between East and West. The decline of the Mongol Empire saw a corresponding reduction in the importance of the Royal Road, which eventually ceased to be a major trade route by around 1453 CE.