 In major transit hubs, such as the Île-de-France region surrounding Paris and the Frankfurt area, major national highways converge just outside city limits before forming one of several routes of an urban network of roads circling the city.Unlike in United States, route numbering is not a challenge on European ring roads as routes merge to form the single designated road.However, exit and road junction access can be challenging due to the complexity of other routes branching from or into the ring road.