
Lateral signal taken over by 'SACEM' (X)

Inside an 'MI 84' during rush hour
The 'RER A' is one of the five lines in the
RER urban rail system serving the
Ăle-de-France ''
région'', notably
Paris and its agglomeration.
The line runs from ''Saint-Germain-en-Laye (
A1), Cergy Le Haut (
A3), and Poissy (
A5). To Boissy-Saint-Léger (
A2) and Marne-la-Vallée - Chessy (
A4)''
★ First inauguration:
December 9,
1977
★ Length: 108.5 km (67.4 miles)
★ Number of stops: 46
★ Traffic (2004): 272,800,000 journeys per annum ''(figure only for the RATP section of the line)''
Line A is Europe's busiest line with over 1,000,000 passenger/day. Line A is formed from the connection across Paris of the
Saint-Germain-en-Laye-
Nanterre line in the west to the
Vincennes â
Boissy-St-Léger line in the east. Two branches were added in the West, to
Poissy and the 'ville nouvelle' of
Cergy, and another in the East, to the ville nouvelle of
Marne-la-Vallée. The two latest extensions of the line were to
Cergy-Le Haut and
Disneyland Resort Paris.
Popular success and responses
Line A has been a runaway success since its inauguration and, with its million-plus passengers per workday, has frequently been presented as the busiest urban transit line in the world. This claim has been disputed (Gerondeau C, 2003 — see reference) by reference to the figure of 103,080 passengers per hour claimed by the Japanese Ministry of Transport for the JR Chëà Line in Tokyo — almost twice the equivalent figure (55,000) for the RER Line A (both 1992). Japan being something of a case apart in the field of rail transport, accounting for 40% of all train journeys in the world, it clearly remains the case that the RER Line A is an exceptionally busy route.
Ever-increasing traffic volume and the need to ward off imminent saturation have been major factors in RATP and SNCF's planning since the inauguration of the Line A. At least five major capital investment decisions can be directly traced back to this issue:
★ In the early 1980s RATP contracted German conglomerate
Siemens to develop a dynamic traffic control system that would remove the capacity constraints caused by conventional block traffic management. This system, called SACEM (''
SystĂšme d'aide Ă la conduite, Ă l'exploitation et Ă la maintenance''), remains today one of the world's most advanced traffic control systems and enables extremely short spacing (under 90 seconds in stations, under 2 minutes in tunnels) between trains during rush hour. (Parisians have become used to the sight of a train pulling into a station as the one before it is just clearing the platform.)
★ Around the same time, RATP had to order a significant number of additional MI79/MI84 trains to remedy premature wear and tear on its existing MS61 rolling stock caused by over-utilization of Line A.
★ Later in the 1980s, the need to relieve congestion on the central segment of Line A was a key factor in selecting the route of the new, fully automated
Line 14 (also known as METEOR) of the
Métro.
★ The same need governed the choice of the route of RER Line E in the early 1990s and is a factor in current plans for that line's westward or south-westward extension.
★ An entirely new class of double-decker trains (
MI 2N series) entered service in 1998, in part a product of RATP's belief that no further infrastructure improvement (short of an extremely expensive track quadrupling) would relieve congestion on Line A.
One simple (if partial) solution to the congestion problem that has never been implemented is a change in the seating configuration inside the trains themselves. The RER is unusual among high-capacity urban train networks in its attachment to "transversal" (front and back facing) seating. A change to "longitudinal" (sideways window-lining) seating typically reduces the number of seats by 10% but increases standing room by 30%. The result is increased capacity and a less cramped ride for those without seats.
Chronology
★ '
December 14 1969': The Paris subway operator, the
RATP, buys the "ligne de Vincennes" from the
SNCF which connected
Bastille with
Boissy-Saint-Léger in the east. A new 2.5-km tunnel was built between
Vincennes and
Nation, which replaced Bastille as the terminus. Total length of segment: 17.5 km.
★ '
February 21 1970': The RATP buys the "ligne de St-Germain" from the SNCF which connected
St-Lazare train station with
Saint-Germain-en-Laye in the west. A new tunnel was opened between
La Défense and the
Place de l'Ătoile, which replaced St-Lazare as the terminus. Shuttle ("navette") service operated
La Défense -
Ătoile, 4 km.
★ '
November 23 1971': Tunnel opened
Ătoile -
Auber, 2 km. Shuttle service extended to operate
La Défense -
Auber.
★ '
October 1 1972': Tunnel opened
La Défense -
Nanterre-Université, 2 km. Shuttle service extended on the "ligne de St-Germain" (
La Défense -
Saint-Germain-en-Laye, 13 km) to operate
Saint-Germain -
Auber.
★ 'October 1973': New underground station,
Nanterre-Préfecture, opened between
La Défense and
Nanterre-Université.
★ '
December 9 1977': Both lines are connected with a new 6-km tunnel giving the birth to the 'RER A' line,
Saint-Germain -
Boissy-Saint-Léger, 42.5 km total. Two new stations were inaugurated:
ChĂątelet-les Halles and
Gare de Lyon. A new branch, "ligne nouvelle de Marne-la-Vallée," 8.5 km, was opened in the east from
Vincennes to
Noisy-le-Grand.
★ '
December 19 1980': The "ligne nouvelle de Marne-la-Vallée" was extended from
Noisy-le-Grand to
Torcy, 9 km.
★ '
May 29 1988': New service, "Interconnexion Ouest,"
Cergy-St-Christophe - Marne-la-Vallée (
Torcy), 47 km total. Included new branch in the west from
Nanterre-Université to
Cergy-St-Christophe, 15.5 km.
★ 'May 1990': Another branch was created in the west from
Maisons-Laffitte to
Poissy, 8.5 km.
★ '
April 1 1992': The Marne-la-Vallée line was extended from
Torcy to
Marne-la-Vallée-Chessy, 11 km, in order to create a direct link from the centre of Paris to
Disneyland Paris.
★ '
August 29 1994': Extension opened
Cergy-St-Christophe â
Cergy-Le Haut, 2.5 km. New station, Neuville-Université, opened. Located between Conflans-Fin-d'Oise and Cergy-Préfecture.
★ '
June 10 2001': New station, Val-d'Europe, opened. Located between Bussy-St-Georges and Marne-la-Vallée-Chessy.
Map

Geographically accurate path of the RER A
List of RER A stations
★ A1
★
★
Saint-Germain-en-Laye
★
★
Le VĂ©sinet â Le Pecq
★
★
Le VĂ©sinet â Centre
★
★
Chatou â Croissy
★
★
Rueil-Malmaison
★
★
Nanterre â Ville
★
★
Nanterre â UniversitĂ©
★ A3, A5
★
★ A3
★
★
★
Cergy â Le Haut
★
★
★
Cergy â Saint-Christophe
★
★
★
Cergy â PrĂ©fecture
★
★
★
Neuville â UniversitĂ©
★
★
★
Conflans â Fin d'Oise
★
★
★
AchĂšres â Ville
★
★ A5
★
★
★
Poissy
★
★
★
AchĂšres â Grand Cormier
★
★
Maisons-Laffitte
★
★
Sartrouville
★
★
Houilles â CarriĂšres-sur-Seine
★
Nanterre â PrĂ©fecture
★
La Défense
★
Charles de Gaulle - Ătoile
★
Auber
★
ChĂątelet - Les Halles
★
Gare de Lyon
★
Nation
★
Vincennes
★ A2
★
★
Fontenay-sous-Bois
★
★
Nogent-sur-Marne
★
★
Joinville-le-Pont
★
★
Saint-Maur â CrĂ©teil
★
★
Le Parc de Saint-Maur
★
★
Champigny
★
★
La Varenne â ChenneviĂšres
★
★
Sucy â Bonneuil
★
★
Boissy-Saint-Léger
★ A4
★
★
Val de Fontenay
★
★
Neuilly-Plaisance
★
★
Bry-sur-Marne
★
★
Noisy-le-Grand â Mont d'Est
★
★
Noisy â Champs
★
★
Noisiel
★
★
Lognes
★
★
Torcy
★
★
Bussy-Saint-Georges
★
★
Val d'Europe
★
★
Marne-la-VallĂ©e â Chessy
Operation
Branches
Line A provides two groups of services:
★ St Germain branch — common trunk line — Boissy branch
★ Cergy or Poissy branches — common trunk line — Marne la VallĂ©e branch.
During off-peak hours, the Cergy-Torcy and Poissy-Chessy services operate every 20 minutes, and the St-Germain - Boissy-St-Leger service operates every 10 minutes.
Operations are very complex during peak periods, with an average of one train every 2 minutes on the common trunk line in the busier direction (east to west in the morning, west to east in the evening), and one train every 2 min 30 sec in the other direction. The Marne la Vallée branch has the most intensive service.
Names of Services
RER trains do not display the name of the destination station, but instead display a "nom de mission" or "name of service." These are, literally, names used to designate (and distinguish) individual services ("runs"), and are accompanied by a two-digit number.
The first letter corresponds to the destination station (gare d'arrivée):
★ B =
La Défense
★ D =
Noisy-le-Grand Mont d'Est
★ N =
Boissy-St-Léger
★ O =
Torcy
★ Q =
Marne-la-Vallée - Chessy
★ R =
La Varenne-ChenneviĂšres
★ T =
Poissy
★ U =
Cergy - Le Haut
★ W = No Passengers ('Train vide,' "Empty Train")
★ X =
Le Vésinet - Le Pecq
★ Y =
Rueil-Malmaison
★ Z =
Saint-Germain-en-Laye
(The letter "W" is used to represent the two letters "v" in 'v'ide 'v'oyageurs, "empty of passengers.)
The second letter corresponds to the stations served. The letter "E" indicates a train calling at all stations ('omnibus', only on the route
Saint-Germain-in-Laye -
Boissy-St-Léger).
The third and fourth letters are used to form a pronounceable name. These letters are changed when the service number (from 01 to 99 eastward, from 02 to 98 westward) reaches the maximum. Therefore, two services with the first two letters identical serve the same station, e.g. ZEUS and ZEMA (local trains with destination
Saint-Germain-en-Laye, or NELY, NEGE and NEMO (local trains with destination
Boissy-Saint-Léger. The letters ZZ generally indicate that the established service pattern was changed for an unspecified reason, generally a technical problem which disrupted operations.
Morning Peak Periods
Each of these services operates every 10 minutes:
★ Boissy - Le VĂ©sinet-Le Pecq, all stations except Nanterre-Ville.
★ La Varenne - St-Germain, all stations except Chatou-Croissy and Le VĂ©sinet-Centre.
★ Marne-la-VallĂ©e - Chessy - Cergy-le-Haut, all stations except Lognes, Noisiel, Bry-sur-Marne, Houilles and Maisons-Laffitte.
★ Marne-la-VallĂ©e - Chessy - Poissy, all stations except Val d'Europe, Bussy-St-Georges, Lognes, Noisy-Champs and Sartrouville.
★ Torcy - Rueil-Malmaison, all stops except Bry, Neuilly-Plaisance and Nanterre-PrĂ©fecture.
★ Cergy - Torcy, all stops except Maisons-Laffitte, Houilles, Noisiel and Lognes.
★ Poissy - Chessy, all stops except Neuilly-Plaisance and Bry.
★ St-Germain - Boissy, all stops except Le VĂ©sinet-Centre and Chatou-Croissy.
★ Le VĂ©sinet-Le Pecq - La Varenne, all stops except Nanterre-PrĂ©fecture, Vincennes and Fontenay.
Evening Peak Periods
Each of these services operates every 10 minutes:
★ Cergy - Noisy-le-Grand, all stops except Maisons-Laffitte and Houilles.
★ Poissy - Chessy, all stops except Sartrouville, Bry, Noisiel and Lognes.
★ St-Germain - Boissy, all stops except Nanterre-Ville and Nanterre-PrĂ©fecture.
★ Le VĂ©sinet-Le Pecq - La Varenne, all stops except VĂ©sinet-Centre and Chatou-Croissy.
★ La DĂ©fense - Torcy, all stops except Neuilly-Plaisance and Bry.
★ Chessy - Poissy, all stops except Bry and Neuilly-Plaisance.
★ Boissy - Le VĂ©sinet-Le Pecq, all stops.
★ Noisy - Cergy-le-Haut, all stops except Houilles and Maisons-Laffitte.
★ La Varenne - St-Germain, all stops except Fontenay, Vincennes, Nanterre-PrĂ©fecture, Chatou-Croissy and Le VĂ©sinet-Centre.
Off-Peak Hours
Each of these services operates every 20 minutes:
★ Cergy-le-Haut - Chessy.
★ Poissy - Torcy.
This service operates every 10 minutes:
★ St-Germain - Boissy-St-LĂ©ger.
See also
★
List of stations of the Paris Métro
★
List of stations of the Paris RER
External links
★
RATP official website ''(in French)''
★
RATP English speaking website
★
Interactive Map of the RER (from RATP's website)
★
Interactive Map of the Paris métro (from RATP's website)
★
Mobidf website, dedicated to the RER (unofficial) ''(in French)''
★
Metro-Pole website, dedicated to Paris public transports (unofficial) ''(in French)''