Saint-Germain – Boucles de Seine bus network

Development of lines operated by CTCOP

Before the opening to the competition, the line Express A14 was operated by the CTCOP (Compagnie des transports collectifs de l'ouest parisien), this line have many services from La Défense – Terminal Jules Verne.

However, the line A14 were split into many lines and were transferred to Mantois and Poissy – Les Mureaux, excepting the line A14 Chambourcy.

Development of lines operated by Entre Seine et Forêt

On July 31, 1998, the network of Entre Seine et Forêt was created. It consists of seven lines (9A, 9B, 9D, 9G, 10, 18 and 21). The network was operated with fourteen vehicles, including eleven standard buses. The fleet features a distinctive livery consisting of a blue pinstripe and two oak leaves on a white background.^[3]

On September 2, 2019, the network was restructured with many changes through the lines:^[4]

• A new shuttle was created under the name "NEX" and experimented for eight months between Le Mesnil-le-Roi (Quartier Cité) and Gare de Saint-Germain-en-Laye.
• The line 10 abandons his diversion to Le Pecq applicated during Sundays and holidays.
• The line 15 gains some services to Lycée International de Saint-Germain-en-Laye during school days.
• The line 20 is created between the Gare du Vésinet - Le Pecq to Gare du Vésinet - Centre, replacing the line 21M.
• The line 21 is simplified and extended to Gare de Marly-le-Roi, with a better frequency during rush hours.
• The line 21S is created as a school service of Le Pecq (École Félix-Éboué) replacing the old line 21M. However, this line serving a primary school, is limited to students only.

On January 1, 2022, the line 20 was integrated to Argenteuil – Boucles de Seine bus network due to the opening to the competition of transports in Île-de-France.

Development of lines operated by Poissy Aval - Deux Rives de Seine

Before the opening to the competition, the line 8 was integrated to Poissy Aval - Deux Rives de Seine.

Development of lines operated by Résalys

Before the opening to the competition, the old network of Résalys was restructured many times:

• In 1997, the network was operated by the CGEA Transport and serves the communes of Aigremont, Chambourcy, Fourqueux and Saint-Germain-en-Laye with the lines 3B, 3C, 3BC, 3D, 3E, 3F and 3G.
• In 2004, the network was operated by Connex Transport and serves the communes of Aigremont, Chambourcy, Fourqueux and Saint-Germain-en-Laye with lines A, B, C, BC, F, L, M, S, T, TS.
• In 2010, the network was operated by Veolia Transport and serves the communes of Aigremont, Chambourcy, Fourqueux, Mareil-Marly and Saint-Germain-en-Laye with lines R1, R2, R3, R4 and R5. Before the restructuring of the network this year, the commune of Mareil-Marly was served by the line 23 of Courriers de Seine-et-Oise (CSO).^[5]

On September 2, 2012, Transdev gained the operation of Résalys.

On August 30, 2015, a new line R6 was created.

On January 7, 2019, the network was restructured again, with a better frequency of the lines R1, R2, R3, R4 and R5 during rush hours.^[6]

Development of lines operated by Transdev Montesson Les Rabaux

Before the opening to the competition, the line Express 1 was integrated to Transdev Montesson Les Rabaux.

Restructuration of the network

From July 13, 2026, the lines of Saint-Germain – Boucles de Seine were renamed, in accordance with the single regional numbering system planned by Île-de-France Mobilités in order to remove duplicated lines. The new lines will all begin with the prefix "63", followed by the last two digits of the old number, as soon as possible. For Express lines, the number will include the department number (in this case, Yvelines, therefore "78") and the last two digits of the line number. These changes grants better services of the schools of the arrondissement of Saint-Germain-en-Laye and for the Tramway line 13.

The correspondence between old and new numbers is as follows:^[14]