Both lines were built as broad gauge, as far as Rakaia on the Main South Line, reached in June 1873, and Amberley  north of Christchurch, on the Main North Line, reached in 1876.
The two railway lines were built using a broad gauge system, reaching specific points along their routes by June 1873 (Rakaia on the Main South Line) and 1876 (Amberley north of Christchurch on the Main North Line).