The ludi circenses, Rome's most popular and long-lasting public spectacles, were so expensive to stage that they were held in Rome only a few days each year, perhaps seventeen or so in the early Empire. Other Roman cities with racing facilities held chariot races more or less often, depending on what they could afford. As might be expected, those financed by the emperor and staged in the mighty Circus Maximus were by far the grandest and most prestigious, and they naturally attracted drivers and fans from all over the Mediterranean world.

On a typical day when the Circus Maximus or some other racetrack in the capital featured races, huge crowds jammed the facility. Many no doubt stayed to see all the races, which numbered twenty-four per day by the mid-first century A. D. These spectators were a mix...