Happy RER A users! According to the line punctuality bulletin for September that Ile-de-France Mobilités (IDFM, the transport organizing authority) just posted on its website, they use the most reliable RER lines in the network.
Punctuality – that is, the percentage of trains on time at a station compared to the bid ordered by IDFM – reached 95.4% in September, 94.6% cumulatively since the start of the year… and an even more impressive punctuality of 97.5% if we limit ourselves to the middle of the line, in the Paris intra-muros. These good results reflect a timeliness barometer that is “generally stable and in line with established goals,” according to IDFM analysis.
However, they hide major gaps and persistent difficulties in some of them. This is particularly the case on line D, which is now ranked last in the Ile-de-France RER class with a cumulative punctuality rate at the end of September that peaked at just 86.2%. In concrete terms, this means that more than one in 10 trains is late or does not run.
The end of line C is in pain
Long considered the “sickest path in the network,” B maintains a slightly higher level of regularity (with 88.4% on-time in September and an average of 89.4% since the start of the year). It has now reached the minimum performance threshold of 89% set under contract by IDFM to SNCF and RATP who jointly manage the line. But the impact of the recovery plan, implemented from 2024, is still yet to be seen by its users… who will also have to wait longer than expected (perhaps until 2030) for a complete update of the rolling stock and the improvements resulting from it.
Another “worrying” line: the broad C line. In September, the company exceeded the regularity threshold of 90% (contractual goal) and showed quite encouraging results… However, performance was clearly lacking in some of its branches.
This is especially true at the “end of the line”, on the Dourdan/La Norville (Essonne) axis, where the cumulative on-time rate of 82.8% is the lowest on the entire RER network. In contrast, the young line V, created from the former RER C Versailles-Chantiers/Massy branch, continues to accumulate good results with a cumulative punctuality rate of 95.6% that is worthy of a metro.
Users are sure that they will receive compensation
For 4 years, IDFM has provided compensation to train line users who experienced the most delays and malfunctions throughout the year. Reimbursement costs, which can range from half a month to one and a half months of Navigo subscriptions, and will be made next spring, will be allocated to users of train routes whose punctuality is less than 80% for at least three months this year.
Even before the timeliness barometer for the last quarter of 2025 was published, users of the Aulnay-sous-Bois/Mitry-Mory (on line B) and Dourdan/La Norville (line C) axes were already confident of being able to claim this compensation.
