an imperial curator (though probably armed with extraordinary powers) that Corbulo denounced the magistratus and mancipes of the Italian roads to Tiberius. He pursued them and their families with fines and imprisonment for 18 years (21–39 AD) and was later rewarded with a consulship by Caligula, who also shared the habit of condemning well-born citizens to work on the roads. It is worth noting that under the rule of Claudius, Corbulo was brought to justice and forced to repay the money which had been extorted from his victims. Other curatores Special curatores for a term seem to have been appointed on occasion, even after the institution of the permanent magistrates bearing that title. The Emperors who succeeded Augustus exercised a vigilant control over the condition of the public highways. Their names occur frequently in the inscriptions to restorers of roads and bridges. Thus, Vespasian, Titus, Domitian, Trajan, and Septimius Severus were commemorated in this capacity at Emérita. The Itinerary of Antoninus, which was probably a work of much earlier date, republished in an improved and enlarged form, under one of the Antonine emperors, remains as standing evidence of the minute care which was bestowed on the service of the public roads. Construction and engineering Ancient Rome boasted impressive technological feats, using many advances that would be lost in the Middle Ages. Some of these accomplishments would not be rivaled in Europe until the Modern Age. Many practical Roman innovations were adopted from earlier designs. Some of the common, earlier designs incorporated arches. Practices and terminology Roman road builders aimed at a regulation width (see Laws and traditions above), but actual widths have been measured at between and more than . Today, the concrete has worn from the spaces around the stones, giving the impression of a very bumpy road, but the original practice was to produce a surface that was no doubt much closer to being flat. Many roads were built to resist rain, freezing and flooding. They were constructed to need as little repair as possible. Roman construction took a directional straightness. Many long sections are ruler-straight, but it should not be thought that all of them were. Some links in the network were as long as . Gradients of 10%–12% are known in ordinary terrain, 15%–20% in mountainous country. The Roman emphasis on constructing straight roads often resulted in steep slopes relatively impractical for most commercial traffic; over