M-50 (Spain)
The M-50 orbital motorway is the outermost ring road of Madrid and its metropolitan area. It has a length of 85 km and, unlike the other ring roads, doesn't form a closed ring, lacking a connection in the northwest between A-6 and A-1. It runs at an average distance of 13.5 km from the Puerta del Sol. It is managed by the central government. Its construction was financed using a shadow toll system.
Nomenclature
The M-50 name was chosen as the highway is theoretically the fifth ring road in Madrid.
The first ring is formed by the streets that follow the route of Felipe IV's wall of Madrid along the streets known as the Rondas (Ronda de Segovia, Ronda de Toledo, Ronda de Valencia, Ronda de Atocha) and the Bulevares (Génova, Sagasta, Carranza, Alberto Aguilera, Marqués de Urquijo) and the roads linking both.
The second ring is formed by the boundaries of Madrid's 19th Century Ensanche, following the proposed Paseo de Ronda.
Finally, the third and fourth rings are, respectively, M-30 and M-40.