Editing Boulevard Périphérique (section)

==Structure and layout==
[[File:Paris peripherique by night long exposure.jpg|right|upright|thumb|Paris' Périphérique by night at Porte d'Italie]]

The structure of the Boulevard Périphérique is similar to most French [[Autoroutes of France|autoroute]]s, [[United Kingdom|UK]] and [[Commonwealth of Nations|Commonwealth nation]] [[motorway]]s, and [[United States|American]] [[freeway]]s in the following ways:
* It is a two-ring, multiple-lane [[controlled access road]] with no [[Intersection (road)|at-grade]] crossings or [[traffic light]]s. Maximum longitudinal slope is 4%.
* Traffic in opposite directions is separated by a [[median strip]].

But the Périphérique is also different from some of its domestic and foreign counterparts:
* Motorists entering the right-hand lane have the [[right-of-way (traffic)|right-of-way]], i.e. priority over vehicles already on the ring road. This stems from the traditional rules governing Parisian boulevards.
* The right-hand lane is reserved for vehicles entering or preparing to leave the "normal" movement of vehicles in the other lanes, or the Boulevard itself. A solid white line separates recently entered traffic and circulating traffic. This is to prevent entering traffic from disrupting the flow of circulating traffic in the inner lanes, since all traffic would otherwise have to yield to any entering traffic, across all lanes.
* There is no [[Shoulder (road)|hard shoulder]] (emergency lane), except around the Porte de Gentilly. This means that crashes can cause considerable disruption to traffic, making it difficult for [[emergency service]]s to reach the scene of a crash.

There are generally four lanes in each of the two rings of the Boulevard. Variations exist:
* A two-lane section between the Porte d'Italie and the Porte d'Orléans
* A five-lane section between the Porte de Montreuil and Porte de Bagnolet
* A three-lane section between the Porte d'Orléans and the Porte de Sèvres.

The entire Boulevard Périphérique is 35.04 kilometres long, as measured along the central median strip. The route closely follows the municipal boundaries of Paris, but diverges in the [[Bois de Boulogne]] and [[Bois de Vincennes]] (where the roadway is [[Tunnel#Cut-and-cover|cut and covered]]), and the [[Paris Heliport]]. Because the Boulevard was built over the old [[Thiers Wall]], its entrance/[[exit ramp]]s and [[interchange (road)|interchanges]] coincide with locations of the wall's former [[City gates of Paris|city gates]], or ''portes''. The road crosses the [[Seine|River Seine]] via bridges upstream at Charenton/Bercy and downstream at Saint-Cloud/Issy.

Small distance markers are distributed evenly alongside the roadway:
* The 00.0 kilometre point is over the River Seine, upstream of the Porte de Bercy, at the bridge's [[expansion joint]]s.
* Distances from this point increase in the clockwise direction.
* The distance markers on the sign are underlined in red on the inner ring road, and in blue on the outer ring.

The roadway varies in elevation:
* 50% is elevated above its surroundings, i.e. above [[Grade (slope)|grade]].
* 40% is constructed in trench sections, i.e. below grade.
* 10% is at ground level, i.e. at grade.

The Boulevard Périphérique can carry the heaviest vehicles allowed by French regulations. There is a height restriction of 4.75 metres (15 feet, 8 inches).