R3 (RER Vaud)

The R3 is a railway service of RER Vaud that provides hourly service between Vallorbe and Aigle in the Swiss canton of Vaud. A limited number of trains continue to St-Maurice. Swiss Federal Railways, the national railway company of Switzerland, operates the service. The service was previously known as the S3.

Operations
The R3 operates every hour between Vallorbe and Aigle, using the western end of the Simplon line. The R3 makes all local stops between Vallorbe and Cossonay-Penthalaz and between Lausanne and Aigle. The R3 is paired with the R4 between Le Day and Aigle, providing half-hourly service. The R4 makes a limited number of stops between Lausanne and Aigle. Both the R3 and R4 provide limited service beyond Aigle to St-Maurice.

History
The "first" S3 was one of the six original lines of the RER Vaud, then called the Vaud Express Network (Réseau express vaudois, REV), when that system was established in December 2004. It ran hourly between Allaman and Villeneuve, on the Simplon line. With the December 2020 timetable change, the S3 was cut back to Lausanne, with the S5 taking over the Lausanne–Villeneuve service.

The RER Vaud lines were substantially reorganized for the December 2022 timetable change. The "new" S3 was a combination of the former S2 and S5, making local stops on the Simplon line between Vallorbe and Aigle, with limited service from Aigle to St-Maurice. On 10 December 2023, all RER Vaud lines were renamed as "R" and a number, instead of "S."