imperial post to keep up-to-date licenses. If there was a dispute on the validity of one of these diplomas a judge would be asked to settle the conflict. These documents were handed out rarely due to the high cost in using and maintaining the cursus publicus. This organization would deliver mail, military equipment and taxes. Alongside this, they also worked as an imperial intelligence agency. Although the government supervised the functioning and maintenance of the network of change stations with repair facilities (mutationes) and full service change stations with lodging (mansiones), the system was not a postal service in the same way as the modern British Royal Mail, nor a series of state-owned and operated hotels and repair facilities. As Altay Coskun notes in a review of Anne Kolb's work done in German, the system "simply provided an infrastructure for magistrates and messengers who traveled through the Empire. It consisted of thousands of stations placed along the main roads; these had to supply fresh horses, mules, donkeys, and oxen, as well as carts, food, fodder, and accommodation." The one who was sending a missive would have to supply the courier, and the stations had to be supplied out of the resources of the local areas through which the roads passed. As seen in several rescripts and in the correspondence of Trajan and Pliny, the emperor would sometimes pay for the cost of sending an ambassador to Rome along the cursus publicus, particularly in the case of just causes. Alongside this, there were relay points or change stations (stationes) provided horses to dispatch riders and (usually) soldiers as well as vehicles for magistrates or officers of the court. The vehicles were called clabulae, but little is known of them. Despite this, they carried out their duties on foot. Augustus, at first, followed the Persian method of having mail handed from one courier to the next, but he soon switched to a system by which one man made the entire journey with the parcel. Although it is possible that a courier service existed for a time under the Roman Republic, the clearest reference by Suetonius states that Augustus created the system. Suetonius states: Another term, perhaps more accurate if less common, for the cursus publicus is the cursus vehicularis, particularly in the period before the reforms of Diocletian. At least one praefectus vehiculorum, Lucius Volusius Maecianus, is known; he held the office