The Bremgarten–Dietikon railway line (German: Bremgarten-Dietikon-Bahn BD) is a railway line in Switzerland. It connects Wohlen and Bremgarten in the canton of Aargau with Dietikon in the canton of Zürich. Passenger service on the line now forms part of the Zürich S-Bahn branded as the S17 and a frequent service is provided with trains running up to every 15 minutes.The line was opened in stages and under different ownership between 1876 and 1912.
