Final answer:
Roads were essential for sending messages across the Persian Empire, as they provided a well-maintained network for communication. Messengers would travel along the roads, changing horses at stations, to cover long distances quickly.
Step-by-step explanation:
Roads played a crucial role in sending messages across the Persian Empire. The empire relied on a network of well-maintained roads, such as the Royal Road, to facilitate communication between the satraps and the king. These roads were equipped with inns, resting places, and waystations, as well as stationed troops for safety. Messengers would travel along the roads, changing horses at the stations to cover long distances in a short time.