Paris has a very well organized public transportation system, which is administered by the state owned company RATP. The system consists of 14 metro lines, 58 bus routes and 4 RER lines.
Single tickets and carnets (bunch of 10 tickets) can be purchased. The best buy is a Paris Viste ticket which is valid for 1-5 days and can be used interchangeably on the metro, RER trains, buses, the Montmartre bus and funicular, and even Île-de-France SNCF trains. It is necessary to keep the ticket till the end of the journey.
353 million passengers use the Paris bus network every year. 1,373 vehicles are operated on a total of 59 lines, with 1,831 stops.
Buses run from approximately 07.00 to 20.00. Exact hours vary according to each bus line with some operating until 00:30. Many of them do not run on Sundays or holidays.
Bus route maps are posted at the bus stops. A single ticket is required to ride most bus lines. An additional ticket is required for each transfer. Special fares apply to Orlybus, Roissybus, Noctilien and Balabus (special bus for tourists).
The city's periphery is served by 3 bus lines that make up the Petite Ceinture (Little Belt), or PC. A single ticket is required to ride any one of these. On Sunday and holidays, Balabus departs from the Gare de Lyon for a 2-hour tour of the city finishing at the Grande Arche de la Défense.
This is a small funicular in Montmartre transporting passengers to the summit of the butte Montmartre and back down again.
The funicular is operated by the Paris Independent Transport Authority (the RATP). You can use it with the same Métro tickets you use in the Paris public transport system. It is a welcome alternative to the rather daunting stairway that you must otherwise climb to reach the summit.
The easiest way to get around Paris is by métro which runs daily from 5:30 a.m.-12:30 a.m. Transportation maps are available at subway stations.
With one single métro ticket you can go anywhere within city limits as long as you don't go out of the station where you are connecting from one line to another. They are available at the stations and from tobacconist’s and must be validated before boarding.
The RER offers rapid transit within Paris along with frequent service to Charles de Gaulle Airport, Versailles, Disneyland Paris, and other suburban destinations.
The RER suburban express network has four lines (A, B, C and D) covering five zones and running between 05.00 - 00.00. The system is linked by the metro network and some SNCF trains.
Métro and RER tickets are interchangeable within the city of Paris (more specifically, in zones 1 and 2 of the Métro/RER network). You can buy an individual ticket or a carnet of 10 tickets at the ticket window of any Métro or RER station or from vending machines.
For travelling beyond the city limits, you need a point-to-point ticket. The fare depends on how far you are travelling. Check the zone map in the RER station or indicate your destination to the counter clerk when buying your ticket. Better yet, use the RER's automated vending machines. (The newer machines are easy to use; just pick your language and follow the instructions. You can pay for tickets with cash or a credit card.)
Map: www.paris.org/Metro/gifs/rer01.map.jpg