Paris is the centre of a national, and with air travel, international, complex transport system. The modern system has been superimposed on a complex map of streets and wide boulevards that were set in their current routes in the 19th century. On a national level, it is the centre of a web of road and railway, and at a more local level, it is covered with a dense mesh of bus, tram and metro service networks.
Streets and thoroughfares
Paris is known for the non-linearity of its street map, as it is a city that grew 'naturally' around roadways leading to suburban and more distant destinations. Centuries of this demographic growth created a city cramped, labyrinth-like and unsanitary, until a late 19th century urban renovation, overseen by Georges-Eugène Haussmann, resulted in the wide boulevards we see there today. This remained relatively unchanged until the 1970s, and the construction of cross-city and periphery expressways.
More recently, the city began renovations to prioritise public transport systems, and has created 'purpose' lanes dedicated to buses, taxis, and, more recently, cyclists, narrowing the passages reserved for automobiles and delivery vehicles. Although reducing traffic flow within the city itself, this traffic modification often results in traffic congestion at the capital's gateway thoroughfares.
Public transport
Locally, Paris's most-frequented public transport is the Métro network, mostly underground. Across 16 lines, its closely spaced stations (around 500 metres between them on average) allow a connection between any capital quarter to any other, and a few lines extend quite far into the suburbs. This is complemented by a bus route network of 347 lines, and, since 1992, the tramway has made a reappearance with 12 lines in the Île-de-France region (mostly outside the city borders). Paris is also the hub of the Réseau Express Régional (RER), a train network with higher speeds and larger stop spacing compared to the Métro that connects the capital to suburban regions. The Transilien, a rail network radiating from the capital's train stations, provides service to other suburban destinations.
Paris's transport fares consists of the Ticket t+ for single trips with some transfers permitted, and monthly or weekly passes covering transport across the Île-de-France region available on contactless Navigo cards.
Organisation
For the governance of Paris-area public transport, the basic rule of thumb is that the RATP (Régie Autonome des Transports Parisiens) governs all transport within and extending from the Parisian Capital, and the SNCF (Société Nationale des Chemins de Fer Français, the state-owned rail company whose network covers all of France) governs all transport outside of and only penetrating the capital, but there are exceptions to this rule. Metro, Tramway, most of the Bus services and parts of the RER network are run by the RATP. Other sections of the RER, as well as the Transilien, are run by the SNCF.
Métro
Paris's métro has 16 lines, and 12 of these penetrate into the surrounding suburbs. Lines 2 and 6 form a circle within Paris, with most other lines crossing the city diametrically.
RER
The RER (Réseau Express Régional) is a network of regional trains that run far into the suburbs of Paris, with fewer stops within the city itself. From its first line A in 1977, it has grown into a network of five lines, A, B, C, D and E: three (A, B, and D) pass through Paris's busiest and most central Châtelet-Les-Halles station. Line C occupies the path of former railways along the Seine's Rive Gauche quays, and the most recently built line E leaves Paris's Gare Saint-Lazare train station for destinations to Paris's north-east.
Transilien
These are suburban train lines connecting Paris's main stations to the suburbs not reached by the RER. The Transilien lines are named as a play-on-words for the "transit" of "Franciliens," inhabitants of the "Île-de-France" région of which Paris is the capital. lien also means link in French.
Tram
All of Paris's tramways had stopped running by 1937, but this mode of transport has returned recently. Beginning in 1992, two lines (the T1 and T2) were built parallel to the outer boundaries of the capital. The T3 line, opened in stages starting in 2006, runs on grassy track alongside much of the city borders of Paris.
Bus
Paris's bus lines interconnecting all points of the capital and its closest suburban cities. There are 58 bus lines operating in Paris that have a terminus within city limits.