A86 autoroute

The A86 is the second ring road around Paris, France. It follows an irregular path around Paris with the distance from the city centre varying in the range. The south-western section of A86 contains one of Europe's longest urban motorway tunnels known as the, opened in two parts in 2009 and 2011. The tunnel is limited to a height of and commercial vehicles are prohibited as a result.
Although now a complete motorway-standard loop, the A86 is a product of its heavily urban route and piecemeal construction, meaning that there are several points at which one has to Glossary of [road transport terms#TOTSO|turn-off-to-stay-on] and sections which are briefly parts of the A3 and A4 autoroutes.
A86 is a part of the three-ring-road system surrounding Paris and Île-de-France:

Boulevard Périphérique, completed in 1973, roughly an ellipse and limits of Paris city.
A86, completed in 2011, irregular,, similar in size with London's North Circular and South Circular.
The Francilienne, a partial ring, circa in diameter, comparable with London's M25 motorway.

The Grand contournement de Paris, two wide loops bypassing Paris, referred to as the First and Second Solutions, may be considered the fourth and fifth ring roads, but are too far from Paris to be considered real ring roads.

History

Beginnings

The first Paris beltway projects stretching several miles beyond the walls of the city began in the early 20th century. In the 1910s, Eugène Hénard proposed a ring road known as the "route des forts". This would have connected the fortifications surrounding the city which would thereafter have been replaced by parks. Several proposals advanced during the 1919 concours du Grand Paris, including those of contest winner Leon Jaussely and runner-up Alfred Agache, similarly advanced the idea of a banlieue connected by a beltway. Agache's submission encircled the capital in three such roads, all connected by a series of radial expressways.
Between 1932 and 1934, Henri Prost developed the Prost plan, an urban infrastructure expansion roadmap for the region of Île-de-France. The plan introduced several radial expressways, such as the A12 and A13 highways' connection at the Triangle de Rocquencourt. All such expressways were connected by a series of bypasses which formed a loop several miles outside the city.
In 1932, RN-186 was articulated as the main route from Versailles to Choisy-le-Roi. Gradual modifications developed it into a full loop which was relatively far from the city but not classified as an expressway.

Duplex A86

The Duplex A86 is a 10 km long motorway tunnel in Paris, which forms part of the A86. Unlike most tunnels, this one is a single tube, double deck tunnel. It opened in two stages: the northern section opened on 26 June 2009 and the southern section on 9 January 2011. It was initially open between 06:00 and 22:00. From 1 September 2009, it became operational 24/7.
Due to the nature of this tunnel, it has a height restriction of 2 m which precludes large vehicles using the tunnel and has a speed limit of 70 km/h. Motorcycles and vehicles with dangerous goods are also not permitted.