Why does it take so long to replace the tracks?

By 2021, a total of 24 kilometres of track and 27 switches must be completely replaced on the central trunk of the RER A, between Nanterre-Préfecture and Vincennes. To complete track replacement while minimising disruptions and the inconvenience to passengers, RATP ruled out the solution of night-time construction, because it would take years and years to complete the project, and train speeds would have to be reduced to levels incompatible with the need to transport more than a million passengers daily. Instead, RATP opted to conduct the construction work in phases, with the total closure of stations along key segments of the RER A each summer as follows:

- Total closure 24 hours a day, 7 days a week during a 4-week period each summer until 2018

- Partial closure at night and on weekends between 2019 and 2021.

Click here for more information on the 2015-2021 line closure calendar.