RER A

RER line A is one of the five lines in the RER system serving Paris, France.

The line runs from the western termini of Saint-Germain-en-Laye (A1), Cergy Le Haut (A3) and Poissy (A5) to the eastern termini of Boissy-Saint-Léger (A2) and Marne-la-Vallée – Chessy (A4).

• Inaugurated: 12 December 1969
• Length: 108.5 km (67.4 mi)
• Number of stops: 46
• Traffic (2007): 300,000,000 journeys per annum (figure for both the RATP and SNCF section of the line)

Line A serves over 1,200,000 passengers per day. It is formed from the connection of the Saint-Germain-en-Laye-Nanterre line in the west to the Vincennes – Boissy-St-Léger line in the east. Two branches were added in the west, to Poissy and the new town of Cergy-Pontoise, and in the east to the new town of Marne-la-Vallée. The two latest extensions were to Cergy-Le Haut and Disneyland Paris.

Popular success and responses

With more than one million passengers per workday, line A is the busiest Parisian urban rail line. 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. 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. SACEM (Système d'aide à la conduite, à l'exploitation et à la maintenance) is still one of the 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 ordered a significant number of MI79/MI84 trains to remedy premature wear and tear on MS61 stock caused by over-utilization on 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 Paris Métro Line 14 (also known as METEOR).
• The same need governed the choice of the route of RER Line E in the early 1990s and is a factor in plans for that line's westward or south-westward extension.
• A new class of double-deck 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 of the central section) would relieve congestion on Line A. This was followed in 2011 by the MI 09 double-decker stock, aimed at replacing the aging MI 84 and MS 61 stocks.

Chronology

• 14 December 1969: RATP buys the "ligne de Vincennes" from SNCF, connecting Bastille with Boissy-Saint-Léger in the east. A new 2.5-km tunnel between Vincennes and Nation, which replaces Bastille as the terminus. Length: 17.5 km (10.9 mi).
• 21 February 1970: RATP buys the "ligne de St-Germain" from SNCF, connecting the Gare Saint-Lazare with Saint-Germain-en-Laye in the west. A new tunnel between La Défense and the Place de l'Étoile, which replaces St-Lazare as the terminus. Shuttle ("navette") service is operated La Défense – Étoile, 4 km (2.5 mi).
• 23 November 1971: Tunnel opened Étoile – Auber, 2 km (1.2 mi). Shuttle service extended to operate La Défense – Auber.
• 1 October 1972: Tunnel opened La Défense – Nanterre-Université, 2 km (1.2 mi). Shuttle service extended on the "ligne de St-Germain" (La Défense – Saint-Germain-en-Laye, 13 km (8.1 mi)) to operate Saint-Germain – Auber.
• October 1973: New underground station, Nanterre-Préfecture, between La Défense and Nanterre-Université.
• 9 December 1977: The lines are connected by a 6-km tunnel, giving birth to the RER A line, Saint-Germain – Boissy-Saint-Léger, 42.5 km (26.4 mi). Two new stations: Châtelet-les Halles and Gare de Lyon. A new branch, "ligne nouvelle de Marne-la-Vallée", 8.5 km (5.3 mi), in the east from Vincennes to Noisy-le-Grand.
• 19 December 1980: The "ligne nouvelle de Marne-la-Vallée" extended from Noisy-le-Grand to Torcy, 9 km (5.6 mi).
• 29 May 1988: New service, "Interconnexion Ouest", Cergy-St-Christophe – Marne-la-Vallée (Torcy), 47 km (29 mi). New branch in the west from Nanterre-Préfecture to Cergy-St-Christophe, 15.5 km (9.6 mi).
• May 1990: A branch in the west from Maisons-Laffitte to Poissy, 8.5 km (5.3 mi).
• 1 April 1992: The Marne-la-Vallée line extended from Torcy to Marne-la-Vallée-Chessy, 11 km (6.8 mi), to create a link from the centre of Paris to Disneyland Paris.
• 29 August 1994: Extension opened Cergy-St-Christophe – Cergy-Le Haut, 2.5 km (1.6 mi). New station, Neuville-Université, between Conflans-Fin-d'Oise and Cergy-Préfecture.
• 10 June 2001: New station, Val-d'Europe, between Bussy-St-Georges and Marne-la-Vallée-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 Vallée branch.

During off-peak hours, the Poissy – Noisy services operate every 20 minutes plus a La Défense – Noisy service every 20 minutes, and the St-Germain – Boissy and Cergy – Chessy services operate every 10 minutes.

Operations are very complex during peak periods, with an average of one train every 2 minutes (30 trains / hour) 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 (24 trains / hour). The Marne la Vallée branch has the most intensive service.

Text imported from Wikipedia article "RER A" and modified on July 22, 2019 according to the CC-BY-SA 4.0 International license.