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 lines were built using a broad gauge system, reaching Rakaia on the Main South Line by June 1873, and Amberley north of Christchurch on the Main North Line by 1876.