Since antiquity, Amiens has been a crossroads of important routes. The contemporary city is served by the A16 and A29 autoroutes. The Jules Verne Viaduct, long, crosses the River Somme to the east of the city and allows circumvention of the city by motorway-type roads. The A16 and A29 autoroutes, the RN1 and the RN25 form a bypass-type motorway around the city that the population has called the "Rocade d'Amiens" road of Amiens. Initially constituting national roads which are downgraded today, mostly as departmental roads, the greater urban area of Amiens is served by: