From BOUDICCA'S REBELLION AD 60-61 The Britons rise up against Rome by Nic Fields

 Republican denarius (Oxford, Ashmolean Museum), struck in c.48 BC by L(ucius) HOSTILIUS SASERNA. It shows a seated charioteer and a standing warrior riding into action on a Celtic chariot. The carriage superstructure has double arched sides, within each arch a Y-configuration. It is possible that the Y was a braided rawhide thong, the four of which suspended a springy riding platform of strapwork. Clearly the arch and Y strap suspension system made the Celtic chariot an effective (almost) all-terrain war machine. (Ashmolean Museum, University of Oxford, UK/Bridgeman Art Library)