Vanderbilt anthropologist Kristina Killgrove explains a lot about crucifixion in an article entitled Line on the left, one cross each: Bioarchaeology of Crucifixion:
The Romans practiced crucifixion – literally, "fixed to a cross" – for nearly a millennium. Like death by guillotine in early modern times, crucifixion was a public act, but unlike the swift action of the guillotine, crucifixion involved a long and painful – hence, excruciating – death. So crucifixion was both a deterrent of further crimes and a humiliation of the dying person, who had to spend the last days of his life naked, in full view of any passersby, until he died of dehydration, asphyxiation, infection, or other causes. The Roman orator Cicero noted that "of all punishments, it is the most cruel and most terrifying" and Jewish historian Josephus called it "the most wretched of deaths."
. . . Only one bioarchaeological example of crucifixion has ever been found. In 1968, Vassilios Tzaferis excavated some tombs in the northeastern section of Jerusalem, at a site called Giv’at ha-Mivtar. . . .
Well worth reading!