In Courtabœuf, the bus is just more.
Why are lines 2, 21, 22 and 23 being upgraded?
Until now, lines 2, 22 and 23 had different routes depending on the time of day, with stops served only in one direction or not served on Saturdays. They also operated by half-day on weekdays. Île-de-France Mobilités has chosen to simplify and strengthen the service offer for the Courtaboeuf business park.
The restructuring implemented on 22 April 2025 makes it possible to improve readability and rationalise the bus service: from 4 to 3 new, clearer lines to facilitate travellers' travel and encourage users to take the bus. These lines are redesigned to allow access to all areas of Courtaboeuf from Massy-Palaiseau station.
This evolution is also an opportunity to integrate the new regional numbering for the three new lines with the prefix "46" while waiting for a change in the numbering of the other lines in the territory to come.
This restructuring brings:
- Better readability of the service: the two main lines now have an identical route for the outward and return journeys and the stops will be served in both directions (towards Massy and towards Les Ulis). Line 4622 operates in a circular way via Courtabœuf from Massy-Palaiseau. New districts of Les Ulis are linked to the Courtaboeuf area, such as the Cévennes.
- Continuous service all day: These three lines run all day. On Saturdays, the Canada / Baltic (line 4602) and Parana (4621) sectors also benefit from a bus service. This provides access to certain facilities in the tertiary industry, particularly services (hotels).
- A wider range of hours: The operating range is extended in the evening. On the 4602 route, the service always starts at 4:30 a.m. on weekdays but ends around 1:30 a.m., Monday to Sunday. The timetable allows you to connect with the last RER B coming from Paris (towards Saint-Rémy-Lès-Chevreuse). The extension of the amplitude of line 4621 also offers additional service to the Parana sector.
Departing from Massy-Palaiseau, these 3 new lines serve the "Château d'Eau" stop.
The 4602 line
Your line 4602 connects the Ulis 2 Shopping Centre to Massy-Palaiseau station.
It serves the Canada and Baltic sectors of the Courtaboeuf business park.
In Les Ulis, it serves the districts of Béarn, Saintonge, Périgord, Anjou Île de France, Bourogne and Alsace.
For simplicity, the itinerary is identical all day long on the outward and return journeys.
» Operation : Monday to Sunday
» Amplitude : 4:30 to 1:30
» Weekly frequency : 6 minutes during rush hour and 15 minutes on peak
» Saturday frequency : 15 minutes
» Sunday frequency : 30 minutes
The 4621 line
Your line 4621 connects the Ulis 2 Shopping Centre to Massy-Palaiseau station.
It serves the Parana sector of the Courtaboeuf business park.
In Les Ulis, it serves the districts of the Cévennes, Ventoux, Burgundy, Franche-Comté, Alsace.
For simplicity, the itinerary is identical all day long on the outward and return journeys.
» Operation : Monday to Saturday
» Amplitude : 6:00 a.m. to 11:00 p.m.
» Weekly frequency : 10 minutes during rush hour and 30 minutes during off-peak hours
» Saturday frequency : 30 minutes
Line 4622
Your line 4622 connects Massy-Palaiseau station to the northern area of Courtabœuf.
It serves the Baltic, Norway and Quebec City sectors.
It operates in a loop, departing from Massy-Palaiseau.
» Operation : Monday to Friday
» Amplitude : 6:00 a.m. to 9:30 p.m.
» Weekly frequency : 12 minutes during rush hour and 30 minutes on the slack
The renumbering of the lines in the Paris Saclay territory
Why does the number of the lines change?
The Ile-de-France bus network is made up of about 1900 lines, with numbering systems that coexist, but which are not alike.
Currently, there are very different names (12, 114, DM10A, etc.), which complicates the understanding of the network.
How to find your way around the new issues?
Île-de-France has been divided into departments and sectors, each with a specific code, according to where the line operates.
The renumbering of the lines in the Paris Saclay territory
On the territory of Paris Saclay, all regular bus lines will now start with " 46 " Ex: line 2 becomes line 4602.
Express line numbers begin with the number of their department. Ex: the Express line 91-05 becomes 9105.
What will this new number bring to travelling customers?
Passengers will be able to find their bus line more easily when searching on the app or the iledefrance-mobilites.fr website, as it will be the only one in Île-de-France to have this number.
When do the lines change number?
With the exception of lines 4602, 4621 and 4622, which will be integrated into regional numbering from 22 April, all lines in the Paris Saclay area will change their numbers in the autumn of 2025.